US20170307282A1

Movatterモバイル変換

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Publication number: US20170307282A1
Application number: US15/513,468
Authority: US
Inventors: Simon Philip Jelley; Stuart Mark Banister; Andrew David CHAPMAN
Original assignee: 42 Technology Ltd
Current assignee: 42 Technology Ltd
Priority date: 2014-09-22
Filing date: 2015-09-22
Publication date: 2017-10-26
Also published as: WO2016046528A1; EP3198205A1; GB2530327A; GB201416666D0

Abstract

Disclosed herein is a heat transfer device (2), the heat transfer device comprising a heat exchanger (10) driven by movement of a fluid, a heat transfer cavity (6) and a fan (12) for creating a circulating gas flow between the heat exchanger and the heat transfer cavity. The heat transfer device (2) includes: a housing having an opening (14) for allowing an object to be inserted into the heat transfer cavity (6); an outlet valve (52) for exhausting gas and/or liquid from the heat transfer cavity (6); and a controller arranged to operate the outlet valve (52). The heat transfer device (2) may, for example, take the form of a cooling device for rapidly cooling a drinking vessel such as a beer glass.

Description

The present invention relates to heat transfer devices that may be used to cool or heat an object to a desired temperature, and corresponding methods of cooling or heating an object. The invention also relates to cooling apparatus and methods of drying a heat transfer device, for example after use.
WO 2011/042698 describes a heat transfer device for hygienic cooling of objects such as drinking vessels. A rapid cooling effect is achieved using turbulence to generate a frosted effect. However this method of rapid heat transfer requires high rates of air circulation e.g. high fan speeds. It may be inefficient to have the fan running at high speed all the time and, in addition, there may be potential problems with frost build-up. It would be desirable for a rapid frosting mode to be turned on/off as required. However the very cold temperatures in such a cooling device, and the internal build-up of frost, add to the complexity of achieving reliable means of control. The present invention seeks to improve known heat transfer devices and corresponding methods.
According to a first aspect of the present invention there is provided a heat transfer device comprising: a heat exchanger, a heat transfer cavity and means for creating a circulating gas flow between the heat exchanger and the heat transfer cavity; a housing having an opening for allowing an object to be inserted into the heat transfer cavity; a sensor arranged to provide a detection signal when an object is inserted into the heat transfer cavity; and a controller for adjusting the rate of circulating gas flow in response to a detection signal from the sensor. It will be appreciated that such a device is able to intelligently control the rate of circulating gas flow by using the sensor to detect when an object is inserted into the heat transfer cavity. For example, upon receiving a detection signal from the sensor, the controller may increase the rate of circulating gas flow between the heat exchanger and the heat transfer cavity so as to enter a rapid heat transfer mode. This may be particularly efficient where the heat transfer cavity is arranged to create turbulence in the circulating gas flow. As is discussed in WO 2011/042698, a highly turbulent gas flow has been found to generate a high heat transfer coefficient and thereby accelerate heat exchange with the object. Thus, in preferred embodiments the circulating gas flow may be constrained to pass through a gap adjacent the object that is defined by the heat transfer cavity so as to promote turbulence in the circulating gas flow. This aspect of the invention also includes a method of cooling or heating an object, comprising: creating a circulating gas flow in a heat transfer cavity that can receive an object; cooling or heating the circulating gas flow; sensing when an object is inserted into the heat transfer cavity; and adjusting the rate of circulating gas flow in response to said sensing.
Some of the ways in which the rate of circulating gas flow can be adjusted are discussed further below.
It is important that the sensor can reliably detect when an object is inserted into the heat transfer cavity. While a manual switch could be used to control adjustment of the rate of circulating gas flow, for example activated by a user when/after inserting an object, this requires additional interaction. It is advantageous for the device to automatically detect an object and trigger the rapid heat transfer mode without intervention being required. In some embodiments the sensor comprises at least one contact sensor, for example a mechanical contact sensor such as a microswitch, that may be activated directly or indirectly when an object is inserted into the heat transfer cavity. For example, a contact sensor may be activated directly by the passage of the object through the opening or by the seating of the object in the heat transfer cavity. A pressure pad could be used to detect when an object is present in the heat transfer cavity. Or, in another example, a contact sensor may be activated indirectly by movement of another part that takes place when an object is inserted into the heat transfer cavity, e.g. movement of a seal that closes the opening when an object is not present.
The Applicant has found that the reliability of a contact sensor can be readily degraded by environmental factors. Especially when the heat transfer device is a cooling device, a tendency for ice to build up can interfere with proper operation of a contact sensor. It is therefore preferable for the sensor to comprise at least one non-contact sensor. Appropriate non-contact sensors may include sensors for electromagnetic radiation (e.g. optical, near-infrared, far-infrared, ultraviolet), ultrasound transducers, and capacitive sensors. Some example of contactless sensor arrangements will now be discussed in more detail, however, it is envisaged that other non-contact sensor technologies may also be employed.
In a set of embodiments the non-contact sensor may comprise an active or passive sensor arrangement for electromagnetic radiation or ultrasound. In a passive sensor arrangement, for example, the non-contact sensor may simply comprise a sensor that detects ambient conditions and/or a change due to electromagnetic radiation being emitted, scattered, lensed, obstructed, absorbed or reflected by an object that is inserted in the heat transfer cavity. A passive receiver such as a photocell or photodiode may simply detect changes in light level when an object is inserted, e.g. increased brightness as an object opens a seal that closes the opening or reduced brightness when an object prevents ambient light from reaching the sensor. In other examples the sensor may comprise a vision camera that provides an optical image of the opening and/or heat transfer cavity and uses appropriate software to determine when an object is inserted or present. However such passive optical sensors are sensitive to ambient lighting conditions, which may be highly variable e.g. at different times of day. A heat transfer device used to cool glasses may be located in a bar or nightclub with flashing lights.
In yet other examples, the sensor may comprise an infrared (IR) sensor that detects changes in thermal emission when an object is inserted into the heat transfer cavity, preferably a far-infrared (FIR) sensor. The sensor may comprise a simple IR thermopile or an IR camera that images the infrared radiation emitted by the object and its surroundings. As the object will likely be at a different temperature to the heat transfer cavity when it is first inserted (e.g. a warm object entering a cool cavity), the infrared sensor or camera can use the change in signal or contrast in a thermal image to generate a detection signal. A passive infrared sensor using thermal emission can provide reliable results even if there are changing ambient light conditions. In some embodiments the IR sensor or camera may be positioned above the opening and, optionally, angled to look down on the opening. This may ensure that the sensor has a good view of the normally cold interior environment of the heat transfer cavity and is therefore sensitive to temperature change when an object is inserted into the cavity. In an active sensor arrangement, the non-contact sensor may comprise a radiation emitter and a radiation receiver that detects reflection and/or transmission of the emitted electromagnetic radiation. This can reduce the arrangement's sensitivity to background illumination. For example, the sensor can detect a background radiation reading when the emitter is off and compare this value to the reading when the emitter is on. In addition, or alternatively, the radiation emitter may emit frequencies of the electromagnetic spectrum that are not visible to the human eye, e.g. near-IR or ultraviolet light, so as to avoid light beams that could potentially annoy or distract a user. Ultraviolet may be more readily reflected or scattered by an object being detected, but there may be risks associated with the use of ultraviolet radiation in close proximity to a user who is inserting the object. An infrared sensor arrangement may be preferred for user safety. In particular, a sensor arrangement comprising an infrared emitter operating in a narrow band, e.g. the wavelength range of 800-1000 nm, has the advantage of the receiver being able to readily filter out broadband sources such as artificial lighting. Such arrangement can conveniently be achieved using low-cost emitters (e.g. infrared LEDs) and receivers (e.g. infrared photodiodes) that are readily available.
In various embodiments it can be desirable for a radiation sensor (e.g. operating at visible or infrared wavelengths) to detect an object, such as a drinking vessel, that is made of transparent material e.g. glass or clear plastic. This can make it difficult for the non-contact sensor to operate in a transmission mode as radiation may shine straight through the object. One possibility is for such objects to include opaque markings (for example printed or etched on the transparent material) that can obstruct the transmitted radiation to increase detection. However this may not be feasible or desirable to implement in practice.
Even a reflectance sensor can be hindered by the shiny nature of such materials, making it difficult to differentiate between reflection of the emitted radiation from the object and background reflections from the ambient illumination. A non-contact sensor comprising a radiation emitter and a radiation receiver, operating in a reflection mode, may be angled so as to better pick out reflections from an expected object. However the angle of such reflectance measurements may need to be adjusted for different objects and this can reduce the reliability of the sensor when the device is used with more than one size or type of object, e.g. different glass shapes.
In another example, a non-contact reflectance sensor may use binocular range sensing to determine the distance to an object from a correlation of the radiation reflected and/or scattered by the object. Such a sensor arrangement may be able to differentiate between the weak reflections from a transparent object (such as a glass) and background light reflections. An infrared proximity sensor such as the Sharp GP2Y0A21YK may be suitable.
The Applicant has devised a novel kind of active sensor arrangement, comprising an electromagnetic radiation emitter and receiver, that can detect an object from transmission of the emitted radiation. This arrangement can be particularly suitable for transparent objects that may have a lensing effect on a transmitted beam. In such preferred embodiments the non-contact sensor comprises an electromagnetic radiation emitter and a corresponding electromagnetic radiation receiver arranged on opposite sides of the opening to define a transmission path passing through an object that is inserted through the opening. In the absence of an object the transmission path may be straight. When a transparent object, such as glass drinking vessel, is present in the opening it can have a beam bending effect so that the emitted radiation does not follow the transmission path to reach the receiver. This effect may be optimised by arranging the radiation emitter and receiver at a height (e.g. at, above or below the opening) corresponding to the expected height of a detectable feature on an object when inserted through the opening, for example a height corresponding to the thickened base of a glass or some other feature e.g. etched onto the glass. It can be advantageous for the sensor to be sensitive to objects of a particular height as this can ensure that the device only operates with certain objects, for example intended glassware.
The radiation emitter and receiver may be arranged diametrically on opposite sides of the opening, so as to define a transmission path passing through a region central to the opening. However, the Applicant has surprisingly found that the beam bending effect may be greater for an off-centre transmission path. It is therefore preferable that the radiation emitter and receiver are arranged non-diametrically on opposite sides of the opening, so as to define an off-centre transmission path. This makes it more likely for an intervening object to deflect the emitted radiation from the transmission path so that it does not reach the receiver. The sensor may compare an output from the receiver with a preset threshold to determine when an object is present in the transmission path. Preferably the emitter is a pulsed source of radiation. This enables the sensor to compare the radiation received when the emitter is on and off. In addition, or alternatively, the sensor may filter the output from the receiver so as to be sensitive to a wavelength of the emitted radiation.
Another example of an active sensor arrangement uses ultrasound. The non-contact sensor may comprise an ultrasound transducer or transceiver e.g. arranged to emit an ultrasound pulse and detect reflection of the pulse when an object is inserted through the opening and/or present in the heat transfer cavity. The ultrasound transducer may be continually pulsed and the time-of-flight measured for reflections. A longer time-of-flight for reflections crossing the opening and/or the heat transfer cavity may indicate the absence of an object while a shorter time-of-flight may indicate the presence of an object. A suitable type of ultrasound sensor is the SRF series available from Devantech Ltd. An advantage of such an ultrasonic range sensor is that it may be able to detect the presence of wide range of different objects, regardless of their optical properties. A detection signal provided by an ultrasound transducer may be less sensitive to the build-up of frost on an object being cooled, which could interfere with electromagnetic sensing techniques. Such an ultrasound transduce is preferably waterproof, so as not to be affected by condensation or ice.
In another set of embodiments the non-contact sensor may comprise a capacitive sensor arrangement. Many objects are made of insulating materials, such as ceramic or glass, which have a relatively high permittivity. For example, glass has a relative permittivity of between around 4 and 10, which gives good detectability in air using capacitive sensing. The capacitive sensor arrangement may operate by exciting electrodes to different voltages (e.g. using a high frequency signal) and monitoring current, e.g. the charge transferred for a given voltage change or the lead time between current and voltage. In various examples the capacitive sensor arrangement may comprise at least one electrode arranged to sense a capacitance change indicating proximity of an object inserted through the opening and/or into the heat transfer cavity. Such a capacitive sensor arrangement may comprise a pair of electrodes arranged to generate a fringe field that will be interrupted when an object is inserted into the heat transfer cavity. However, the Applicant has found that off-the-shelf fringe field capacitive sensors may not provide sufficient sensitivity as they typically require an object to approach within a few millimetres for detection. This can cause a problem if objects of different size or dimensions are inserted into the heat transfer cavity. Furthermore, in a cooling device a typical capacitive sensor may be sensitive to frost build-up and provide false readings. For example, the Applicant has found that a thin layer of ice in close proximity to a capacitive sensor can give a reading that is very similar to that of a glass-walled object such as a drinking vessel. The Applicant has devised a novel capacitive sensor arrangement that may be particularly suitable for a heat transfer device in which the heat transfer cavity is shaped to receive a hollow object such as a drinking vessel. The capacitive sensor arrangement preferably comprises a pair of electrodes arranged in the heat transfer device to receive an object therebetween. The electrodes may be at least partially annular and preferably arranged concentrically so that an object, such as a drinking vessel, can be received between inner and outer electrodes. The electrodes may not be fully annular, so as to save on material, but the Applicant has found that a higher surface area is beneficial to help eliminate sensitivity to local ice build-up and improve reliability of object detection. The electrodes may therefore be substantially cylindrical or frustoconical.
In a preferred set of embodiments the heat transfer cavity may be formed, at least in part, by a separable and/or removable ducting member. For example, the ducting member may comprise a generally cylindrical sheath that is shaped to receive an inverted drinking vessel such as a beer glass. It is advantageous for the ducting member to be a separable insert so that it can be removed from the device to be cleaned. A further advantage is that different ducting members may be fitted to match different drinking vessels in use, without needing to change the rest of the device. This can be particularly beneficial when the ducting member defines a gap adjacent the object that is chosen to promote turbulence in the circulating gas flow. In embodiments where the sensor comprises a capacitive sensor arrangement, the ducting member may conveniently position or carry one or more of the electrodes. Although the ducting member may be formed of plastics material(s), it can carry a conductive e.g. metallic layer or conductive coating to form the electrode(s). Where the electrode(s) are carried by the ducting member then a separable electrical connection may be provided. Otherwise the electrode(s) may be positioned inside or outside the ducting member with a permanent electrical connection. In a further set of embodiments the circulating gas flow may be created by a fan positioned inside or below the heat transfer cavity, for example beneath the ducting member. The gas flow may be circulated by the fan through a generally cylindrical exhaust tube that is arranged concentrically inside the ducting member. The exhaust tube can conveniently position or carry one of the electrodes of a capacitive sensor arrangement, e.g. without the need for a separable electrical connection.
Of course it will be appreciated that the heat transfer device may include more than one sensor, in particular one or more of the different sensor arrangements discussed above, in any combination. The use of multiple sensors may provide for increased reliability, with a detection signal being required from more than one sensor before the controller operates. In addition, or alternatively, the use of multiple sensors may provide a failsafe in the event that one of the sensors becomes inoperative e.g. due to frost build-up in a cooling device. In a preferred set of embodiments the sensor(s) are chosen so as to detect when a drinking vessel is inserted into the heat transfer cavity. The sensor(s) may be integrated with an opening and/or heat transfer cavity that are sized or shaped to receive a given type of drinking vessel, for example a particular kind of beer glass. As is mentioned above, the sensor(s) may be arranged so as to provide a detection signal only when a certain type of drinking vessel is inserted, e.g. to prevent the device from being used with certain beer glasses.
There will now be described some further features of the heat transfer device that apply irrespective of the type of sensor.
In some examples the device may not operate when an object is not present, and the rate of circulating gas flow may therefore be increased from zero upon detecting that an object is inserted into the heat transfer cavity. However, in many examples it is preferable for the device to operate at least in a standby mode, with a certain minimum rate of circulating gas flow, so as to help maintain the heat transfer cavity within a certain temperature range even when an object is not present. In a particularly preferred set of embodiments, the heat transfer device is a cooling device and the heat exchanger is a thermal sink arranged to cool the circulating gas flow. For example, the minimum rate of circulating gas flow may be chosen to maintain the heat transfer cavity at a temperature in the range of about −35° C. to −45° C. When the sensor detects that an object has been inserted into the heat transfer cavity, the controller may increase the rate of circulating gas flow so as to enter a rapid heat transfer mode, e.g. a rapid cooling mode that can create a frosted effect on the outer surfaces of the object.
It is preferable that the rapid heat transfer mode continues only for as long as necessary to bring the object to a desired temperature, as the high rate of circulating gas flow might have a high energy demand. Where the heat transfer device is a cooling device, it may not be desirable to prolong the rapid cooling mode as this could result in an unwanted build-up of ice on the object or in the heat transfer cavity. During rapid circulation, any ambient (typically damp) air that leaks into the heat transfer cavity will be mixed in more, and for a cooling device this can cause excess frost as well as requiring extra energy input. In addition, the means for creating the circulating gas flow (e.g. a fan) may dissipate significant energy during operation, both demanding energy and requiring further cooling of the heat transfer cavity, thereby lowering the efficiency of the device. In various examples the rapid cooling mode is terminated once a desired frosting effect has been achieved for the object. Preferably the controller reduces the rate of circulating gas flow after an object has undergone a desired heat transfer treatment.
In a set of embodiments the sensor may further be arranged to detect when an object is removed from the heat transfer cavity. The controller may then adjust the rate of circulating gas flow in response to a further detection signal from the sensor indicating removal of the cooled/heated object. Preferably the controller decreases the rate of circulating gas flow so as to enter a standby mode. As is mentioned above, the standby mode could be one in which the circulating gas flow is turned off completely, or a “keep cold/warm” mode where the gas flow is circulated at a lower rate to maintain the heat transfer cavity within a particular temperature range. However there may be times when an object is inserted into the device and not removed for immediate use but instead left inside the heat transfer cavity. A user may forget to remove the object or may choose to leave the object in a cooled/heated state until it is required. It would be inefficient for the device to maintain the rapid heat transfer mode indefinitely. The device may provide a user alert when the controller determines that an object is ready to be removed, but it may be desirable to switch out of the rapid heat transfer mode without needing to remove the object.
In another set of embodiments, alternatively or in addition, the controller may be further arranged to adjust the rate of circulating gas flow so as to exit the rapid heat transfer mode, e.g. in response to a manual input, a timer signal or a temperature signal. In a first set of examples a user may provide a manual input when it is judged that the object has been heated/cooled to a desired degree. This allows a user to dictate the result that is achieved and makes the device more flexible. However it may instead be desirable to avoid a perception of variability and ensure that a repeatable heat transfer treatment is achieved by the device automatically ending the rapid heat transfer mode.
In a second set of examples, alternatively or in addition, the controller may respond to a temperature signal indicating that the object has reached a desired temperature. The temperature signal may be provided by the same sensor that detects when an object is inserted, or a further sensor, for example a passive infrared sensor. In a third set of examples, alternatively or in addition, the controller may respond to a timer signal. For example, the controller may set a simple time limit triggered by the detection signal when an object is first inserted into the heat transfer cavity. The controller may be programmed with different time limits for different objects, which could be set manually or informed by the detection signal (e.g. based on the type of object that is detected). In at least some examples, the controller may monitor a temperature signal or a timer signal during the rapid heat transfer mode and determine the length of time left in that mode. An audible and/or visible countdown may be provided to inform a user of how long the object needs to stay in the heat transfer device. Of course one or more of these techniques may be provided in the same device, for example a default timer in case a user does not remove the object from the heat transfer cavity or its removal is not detected for some reason. When the controller operates to adjust the rate of circulating gas flow so as to exit the rapid heat transfer mode, a communication signal may be output by the device. The communication signal may comprise an audible and/or visible alert to a user that the rapid heat transfer mode has ended and e.g. the object is ready to be removed. As is mentioned above, as a default the device may operate in a standby mode with a certain minimum rate of circulating gas flow, so as to help maintain the heat transfer cavity within a certain temperature range even when an object is not being rapidly cooled/heated. Where the device is a cooling device, it has been found beneficial to maintain relatively cold temperatures throughout the internal gas flow path by recirculating the cold gas, e.g. so that temperatures remain cold even further away from the heat exchanger. In embodiments where the circulating gas flow is generated by a fan or other mechanical device, such a standby mode can prevent ice build-up from locking the moving parts, as might occur if there was zero circulation in between rapid cooling modes.
In a set of embodiments the device operates in a standby mode where the heat exchanger is operating (e.g. circulating refrigerant through heat exchange coils) and there is a gas flow circulating between the heat exchanger and the heat transfer cavity. The gas flow may be circulated at a lower rate than in the rapid heat transfer mode. Preferably the heat exchanger is driven to provide substantially the same heat transfer rate in the standby mode as in the rapid heat transfer mode (for a given rate of circulating gas flow). For example, refrigerant may be circulated through the heat exchanger at the same rate and temperature. Of course the rate of circulating gas flow does not need to stay constant in the standby mode but could be adjusted, e.g. based on a temperature measurement for the heat transfer cavity. In such a standby mode the heat transfer cavity of a cooling device may, for example, be maintained in a range of about −35° C. to −45° C. This may be considered a “peak” standby mode as the heat transfer cavity is kept at temperature range quite far from ambient and is ready to move into a rapid heat transfer mode at any time. Such a “peak” standby mode would be ideal for a device that is in regular use, for example to frost glasses in a bar during evening service.
The Applicant has recognised that there may be “off-peak” times when it is desirable to keep the device running, but with a lower energy demand, e.g. when objects may still need to be cooled/heated but less frequently than at peak times of use. One option could be to further adjust e.g. reduce the rate of circulating gas flow. However, without a certain rate of recirculation it has been found that ambient air can more readily leak into the heat transfer cavity and quickly change its temperature. Where the heat exchanger is passive, e.g. fins simply arranged to exchange heat with the atmosphere, there may be little scope to change its effect on the circulating gas flow. On the other hand, it has been recognised that an active heat exchanger can provide for control of the cooling/heating effect without necessarily adjusting the rate of circulating gas flow. Thus, in preferred embodiments, the heat exchanger is driven to provide a first heat transfer rate for a given rate of circulating gas flow in a first (“peak”) mode of operation, and a second, lower heat transfer rate for the same given rate of circulating gas flow in a second (“off-peak”) mode of operation. A controller may be arranged to switch between the first and second modes of operation. This is considered novel and inventive in its own right. According to a second aspect of the present invention there is provided a heat transfer device comprising: a heat exchanger, a heat transfer cavity and means for creating a circulating gas flow between the heat exchanger and the heat transfer cavity, wherein, in a first (“peak”) mode of operation, the heat exchanger is driven to provide a first heat transfer rate for a given rate of circulating gas flow and, in a second (“off-peak”) mode of operation, the heat exchanger is driven to provide a second, lower heat transfer rate for the same given rate of circulating gas flow; and a controller arranged to switch between the first and second modes of operation. It will be appreciated that such a device can be controlled so as to switch between “peak” and “off-peak” modes of operation without necessarily adjusting the rate of circulating gas flow. By actively driving the heat exchanger to provide different average heat transfer rates, the temperature of the heat transfer cavity may be allowed to change but the circulating gas flow can ensure that there is an even temperature distribution. This can keep the device primed so that a desired cooling/heating effect is achieved when an object is inserted into the heat transfer cavity and the controller then adjusts the rate of circulating gas flow e.g. so as to enter a third, rapid heat transfer mode. In the context of vapour-compression refrigeration, it will be understood that what is meant by the heat exchanger being “driven” is the heat transfer rate achieved as a result of movement of a coolant fluid therein, for example movement of a refrigerant in the coils of a heat exchanger. This may depend on factors including (but not limited to) the choice of fluid driving the heat exchanger, the fluid flow rate, and the temperature of the fluid before it undergoes heat exchange. In the context of thermoelectric heat transfer using the Peltier effect, the heat exchanger may be “driven” at different heat transfer rates by varying the voltage applied across (or current through) the solid state device. Other types of heat exchanger may also be envisaged that allow for the heat transfer rate to be adjusted e.g. depending on the power supplied to the heat exchanger.
This aspect of the invention also includes a method of cooling or heating an object, comprising: creating a circulating gas flow in a heat transfer cavity that can receive an object; cooling or heating the circulating gas flow; in a first (“peak”) mode of operation, cooling or heating the circulating gas flow at a first heat transfer rate for a given rate of circulating gas flow; in a second (“off-peak”) mode of operation, cooling or heating the circulating gas flow at a second, lower heat transfer rate for the same given rate of circulating gas flow; and switching between the first and second modes of operation.
In preferred embodiments, the controller is arranged to switch to a third mode of operation wherein the given rate of circulating gas flow is adjusted when an object is inserted into the heat transfer cavity. For example, the given rate of circulating gas flow may be increased to provide a rapid heat transfer mode. In the third mode of operation the heat exchanger may also be driven to provide the first, higher, heat transfer rate. Where the device is starting in the second (“off-peak”) mode, the heat exchanger may therefore be adjusted at substantially the same time as adjusting the rate of circulating gas flow. Such a rapid heat transfer mode may be triggered manually or automatically. In examples of the latter, the heat transfer device may comprise a sensor arranged to detect when an object is inserted into the heat transfer cavity. Any of the sensor features described hereinabove may equally apply to such embodiments.
It will be appreciated that the starting temperature of the heat transfer cavity in the third mode of operation may be different, depending on whether the controller has switched from the first (“peak”) mode or the second (“off-peak”) mode to the third mode. Where the heat transfer device is a cooling device, for example, the heat transfer cavity may be warmer starting from the second (“off-peak”) mode. It may therefore take longer to achieve a desired cooling effect, for example to frost a drinking vessel. The time spent in the third mode of operation, for example to achieve rapid cooling of an object inserted into the heat transfer cavity, can be adjusted to take this into account. Thus in a preferred set of embodiments the controller is arranged to switch to the third mode of operation for a time period that is adjusted, preferably lengthened, depending on the preceding mode of operation, e.g. peak or off-peak. During a generally off-peak period of usage, an increased frosting time may be acceptable and can advantageously compensate for the warmer starting temperature of the heat transfer cavity. Accordingly the controller is preferably arranged to switch to the third mode of operation for a time period that is longer when the preceding mode of operation is off-peak rather than peak. This may also be more energy efficient, as it has been found that when the device is used less frequently the heat transfer cavity only warms due to heat gain through its insulation as there is little mixing with ambient air from objects being inserted. However, if the controller were to detect an increase in usage indicating that the off-peak mode is no longer appropriate, then it may act to re-adjust the time period for rapid heat transfer despite the preceding off-peak mode. For example, the controller may react to increased load (e.g. multiple glass frostings requiring a higher throughput) in the third mode of operation to provide a faster cooling period than the lengthened one, despite the preceding off-peak mode, thereby maximising performance and efficiency.
As is mentioned above, the controller may switch from either the first (“peak”) mode or the second (“off-peak”) mode to the third mode of operation, e.g. in response to a detection signal that an object has been inserted into the heat transfer cavity. If the device has been operating in the off-peak mode for some time then it may be desirable to control the heat exchanger so as to move back to the first, higher, heat transfer rate in the third mode. However, if the device has only recently switched to the off-peak mode then there may have been little or no change in the temperature of the heat transfer cavity and no instant need to increase the heat transfer rate. The device may be switched back to the off-peak mode after the third mode has provided for rapid cooling/heating of the object. So as to avoid cycling the heat exchanger unnecessarily, the controller may use a timer to determine whether to change the heat transfer rate at the same time as adjusting the rate of circulating gas flow when entering the third mode. For example, the controller may only switch the heat exchanger to the first, higher, heat transfer rate in the third mode when the timer determines that the device was operating in the second (“off-peak”) mode for a minimum preceding delay, e.g. at least two minutes.
Where the heat transfer rate of the heat exchanger is also dependent on the temperature of the heat transfer cavity, this is assumed to be constant for the purpose of comparing the (average) first and second heat transfer rates. It will be appreciated that the heat transfer rate of the heat exchanger may be actively adjusted in any suitable way. In various embodiments the heat exchanger may form part of a heat exchange circuit driven by movement of a fluid therein to provide the first or second heat transfer rate. For example, the heat transfer rate may be adjusted by controlling the temperature and/or speed of the fluid. Where the heat transfer device is a cooling device, for example, the heat exchanger may form part of a refrigerant circuit driven by a moving coolant fluid e.g. a refrigerant. In the second (“off-peak”) mode of operation the heat transfer rate may be lowered by reducing or stopping movement of the coolant fluid through the heat exchanger, or by reducing the degree of cooling of the coolant fluid before it reaches the heat exchanger. For instance, in a typical refrigerant circuit the coolant fluid is circulated through a compressor (and optionally a condenser) e.g. a condensing unit before being passed to the heat exchanger and this may be controlled. A variable speed compressor may be used. The heat exchange circuit may be controlled in response to a temperature signal from a sensor located in the heat transfer cavity.
In the second (“off-peak”) mode of operation the entire heat exchanger could be pulsed on and off to provide a second heat transfer rate that is, on average, lower than the first heat transfer rate. Even when the heat exchanger is not being actively driven, its thermal mass (for example, the copper coils that carry the coolant fluid) can continue to provide a cooling effect e.g. even when the condensing unit (in particular the compressor) is turned off. This may continue to cool (or heat) the circulating gas flow in the heat transfer cavity. However constant cycling of all the components in a heat exchange circuit, such as a refrigerant circuit, may cause excessive wear or other damage. In some embodiments the heat exchanger may be driven to provide a lower heat transfer rate that is not zero i.e. the heat exchanger keeps running but with a lower heat transfer effect. As is mentioned above, in embodiments where the heat transfer device is a cooling device and the heat exchanger is driven by movement of a coolant fluid provided by a refrigerant device, a lower heat transfer rate may be achieved by circulating the coolant fluid at a reduced rate. This may be beneficial in that it keeps the refrigerant device loaded. In other embodiments the heat exchanger may be turned on and off, but using a timer control to ensure that such cyclic operation is not too frequent, e.g. a minimum time delay of two minutes between switching of the first and second modes.
Where the heat transfer device is a cooling device, in the second (“off-peak”) mode of operation the heat transfer cavity may be maintained at a higher temperature than in the first (“peak”) mode of operation e.g. an off-peak temperature range of about −25° C. to −35° C. compared to a peak temperature range of about −35° C. to −45° C.
In some embodiments the controller may be arranged to switch between the first and second modes of operation in response to a manual input. For example, a user may decide when an off-peak mode is appropriate. Alternatively, or in addition, in some embodiments the controller may be arranged to automatically switch between the first and second modes of operation. For example, the controller may be programmed to intelligently switch between peak and off-peak modes e.g. based on historical or learned usage information. Usage information might include the frequency of use (e.g. how often an object is inserted to be cooled/heated), the time of day, different days of the week, the time of year, and even environmental factors such as the ambient temperature.
In a set of embodiments the controller may switch between the first and second modes of operation in response to a temperature signal from a sensor located in the heat transfer cavity. For example, a cooling device may be switched (back) into the peak mode when warming of the cavity indicates a higher frequency of use. Alternatively, or in addition, in a set of embodiments the controller may switch between the first and second modes of operation in response to a detection signal from a sensor arranged to detect when, and how frequently, an object is inserted into the heat transfer cavity. This may provide for a faster reaction to increased usage than waiting for a temperature indication. As is mentioned above, repeated switching of the heat exchanger may be detrimental and the controller may therefore include a timer to determine when the heat transfer rate was last changed. For example, the controller may only switch back and forth between the first and second modes of operation after a predetermined delay, e.g. at least two minutes.
While the heat transfer device may be operated in various different modes as described above, from time to time the device may be switched off completely and the heat transfer cavity allowed to return to ambient temperature. Especially in embodiments were the heat transfer device is a cooling device, the low internal temperatures of the heat transfer cavity can cause frost i.e. ice crystals to build up. When an object is inserted through the opening, ambient air may be drawn into the heat transfer cavity and, as it cools below its dew point, any water vapour carried by the ambient air will condense and freeze. Much of the resulting frost may be deposited on the outer surfaces of the object, contributing to a frosted effect, but after prolonged periods of use some frost may also start to build up in the heat transfer cavity and path of the circulating gas flow. This can have a detrimental effect on components such as the heat exchanger and a fan (or other means) that create the circulating gas flow. The device may therefore be turned off from time to time so that it can be defrosted.
When a cooling device is turned off and allowed to warm up, any residual ice will melt and water is likely to collect in the heat transfer cavity. Similarly, if a warming/heating device is turned off and allowed to cool down, condensation is likely to form in the heat transfer cavity. The melt water or condensate could be left to evaporate naturally, but this may take some time, especially in more humid climates. The Applicant has recognised that it may cause potential hygiene issues for water to be left stagnating in the device, especially if objects such as drinking vessels are to come into contact with the heat transfer cavity when the device is next used. It is therefore preferable that the device can be operated in a further “defrost” or “warm-up” mode that helps the heat transfer cavity to dry out when the device is no longer in use. Preferably the device includes an outlet valve for exhausting gas and/or liquid from the heat transfer cavity. A controller may be arranged to operate the outlet valve.
According to a third aspect of the present invention there is provided a heat transfer device comprising: a heat exchanger driven by movement of a fluid therein, a heat transfer cavity and a fan for creating a circulating gas flow between the heat exchanger and the heat transfer cavity;
a housing having an opening for allowing an object to be inserted into the heat transfer cavity;
an outlet valve for exhausting gas and/or liquid from the heat transfer cavity; and a controller arranged to operate the fan and/or outlet valve.
Such a heat transfer device is therefore provided both with a main opening for the heat transfer cavity and an additional outlet valve that can be used to drain liquid from the cavity e.g. when it is defrosting. It will be appreciated that an outlet valve, rather than merely an outlet or exit opening, can be opened and closed so as to selectively exhaust fluid from the heat transfer cavity.
This aspect of the invention includes a method of drying a heat transfer device comprising a heat transfer cavity that can receive an object, the method comprising: creating a circulating gas flow in the heat transfer cavity; ceasing to cool or heat the circulating gas flow; and opening an outlet valve to exhaust gas and/or liquid from the heat transfer cavity. The method optionally further comprises: increasing the rate of the circulating gas flow.
In a drying or “defrost” mode of operation the heat exchanger is no longer driven and the controller may open the outlet valve. In addition, the controller may optionally operate the fan so as to create or maintain the circulating gas flow. In preferred embodiments the controller may operate the fan at an increased speed so as to circulate the gas flow more rapidly. The fan may, for example, be operated to create an increased rate of circulating gas flow e.g. corresponding to a rapid cooling mode as described above. The circulating gas flow has been found to help exchange heat and moisture with the external environment through the outlet valve. An increased rate of circulating gas flow can quickly act to clear droplets of water resulting from condensation and/or melted frost. Furthermore, the increased workload on the fan will tend to result in heat dissipation into the heat transfer cavity that can also contribute to the efficiency of the defrost mode, helping to dry out the heat transfer cavity. The fan is preferably in fluid communication with the heat transfer cavity. Further preferably the fan is waterproof e.g. comprising potted or coated electronic components so as to be unaffected by moisture ingest.
The Applicant has recognised that the design and position of the outlet valve can be optimised so as to increase the efficiency of the drying or defrost mode.
In a preferred set of embodiments the outlet valve comprises an outlet opening and the heat transfer cavity comprises an outlet flow path arranged to direct liquid towards the outlet opening. This can assist in draining larger liquid droplets under gravity. The outlet flow path may be inclined (e.g. angled or curved) in one or more directions to ensure that liquid is drained from throughout the cavity. For example, the outlet flow path may be inclined downwardly in a radial direction so as to direct liquid towards the outlet opening. For example, alternatively or additionally, the outlet flow path may be inclined downwardly in a circumferential direction so as to direct liquid towards the outlet opening. In a preferred set of examples, the outlet flow path may provide a helical incline towards the outlet opening. In other words, the surface(s) in the heat transfer cavity may be inclined so as to provide a spiral flow path that directs liquid towards the outlet opening. This is considered novel and inventive in its own right.
According to a fourth aspect of the present invention there is provided a heat transfer device comprising: a heat exchanger, a heat transfer cavity and means for creating a circulating gas flow between the heat exchanger and the heat transfer cavity; a housing having an opening for allowing an object to be inserted into the heat transfer cavity; and an outlet valve for exhausting gas and/or liquid from the heat transfer cavity; wherein the heat transfer cavity comprises an outlet flow path arranged to direct liquid towards the outlet valve.
As is described above, the outlet flow path may be inclined downwardly in a radial and/or circumferential direction so as to direct liquid towards the outlet valve under gravity. The outlet flow path may provide a helical incline towards the outlet valve e.g. a spiral flow path that directs liquid towards the outlet valve.
In addition, or alternatively, in a preferred set of embodiments the outlet valve comprises an outlet opening that is directed substantially tangential to the direction of the circulating gas flow e.g. the outlet opening is directed in the direction of rotation of the fan. This makes it easier for the outlet opening to entrain water droplets that are carried by the circulating gas flow. Any spray that is flung out tangentially by the fan can be collected effectively to drain through the outlet opening. The outlet opening may be substantially positioned at a periphery of the fan. The outlet opening is therefore positioned at a point of high gas pressure relative to the opening of the heat transfer cavity, such that, with the outlet valve open and without a perfect seal at the opening of the heat transfer cavity, the two internal pressures equilibrate each side of the ambient external pressure. In other words, the opening to the heat transfer cavity is at a low pressure part of the air circulation path while the outlet opening is at a high pressure part. As such, the pressure of the gas just inside of the opening of the heat transfer cavity is lower than the ambient pressure so gas is readily drawn into the heat transfer cavity, and the pressure of the gas just inside the outlet opening is higher than the ambient external pressure, causing gas to be readily expelled. A good throughflow of air is therefore created to assist in driving out moisture and drying out the cavity. Smaller liquid droplets will readily evaporate in the circulating gas flow, especially as it is replenished by drier ambient air.
The Applicant has found that the outlet opening, and optionally the outlet flow path, should be unrestrictive to the throughflow of air. If they are sized too small then boundary effects can hinder the flow. Preferably the outlet opening has a cross-sectional area of at least about 50 mm². Where provided, the outlet flow path preferably has a cross-sectional area of at least about 50 mm²along its length. The cross-sectional area of either, or both, of these is further preferably at least about 100 mm², 150 mm², 200 mm², 250 mm², or 300 mm². In a preferred set of embodiments the outlet opening has a cross-sectional area of at least 250 mm², and preferably more than 300 mm², so as to dry out a typical heat transfer cavity for a beer glass in a relatively short period of time e.g. about 20 minutes (depending on ambient conditions). It will be appreciated that such an outlet opening is larger than a standard liquid outlet e.g. provided for drainage purposes without enabling an air flow. In at least some embodiments, the outlet opening may have a maximum cross-sectional area of about 0.25 m². This ensures that the heat transfer cavity is not overly open to the external environment.
While it is beneficial that the outlet opening does not unduly restrict air flow, it has been found that liquid droplets can tend to form around a larger opening and be blown out in all directions. It is desirable to be able to collect any liquid droplets that drain through the outlet opening. Thus in a set of embodiments the device further comprises a funnel arranged adjacent to the outlet valve to collect liquid. The outlet opening may extend orthogonally to the funnel, for example, a generally horizontal outlet opening that directs liquid droplets into a generally vertical funnel. The outlet opening of the valve may include a protrusion, e.g. an angled protrusion, that tends to collect liquid into coalesced droplets. Such a protrusion may be positioned above the funnel so that liquid droplets are directed into the funnel. The funnel may have a smaller cross-sectional area than the outlet opening, especially if the cross-sectional area of the funnel decreases to a minimum along its length. However, it has been found that the proximity of the funnel to the outlet opening means that it can also act to restrict air flow through the outlet valve if the funnel is too narrow. Preferably the funnel has a minimum cross-sectional area of at least about 30 mm², and preferably at least about 50 mm², so that it does not negatively affect the time taken to defrost the device. The device may further comprise a drip tray positioned beneath the funnel, preferably a removable drip tray. Melt water collected in the drip tray can be left to evaporate or the drip tray may be emptied by a user.
The controller may open the outlet valve in the drying or “defrost” mode of operation by any suitable means. So as to ensure that the valve opens reliably regardless of the air pressure in the heat transfer cavity, the outlet valve may be mechanically opened. For example, the controller may operate a servo motor or electromechanical actuator (e.g. solenoid) that moves a cover from the outlet opening. The cover may be a sealing cover, for example an elastomeric e.g. silicone flap. The controller may further operate to close the outlet valve at the end of the defrost mode. This can help to maintain hygiene by ensuring that the heat transfer cavity is not left open to the atmosphere after it has been defrosted. In some examples the end of the defrost mode may be triggered by a timer. Alternatively, or in addition, in some examples the end of the defrost mode may be triggered by a detection signal from a sensor in the heat transfer cavity e.g. a temperature and/or humidity sensor.
In various embodiments the heat transfer device is a cooling device and the heat exchanger is a thermal sink arranged to cool the circulating gas flow. The heat exchanger may be driven by movement of a coolant or refrigerant fluid therein.
There may be times when it is desirable to accelerate the drying or defrost mode. For example, when operating a cooling device in a humid climate there may be times during the day when frost has built up and a quick defrost would be beneficial to prevent the ice from interfering with performance. In a set of embodiments the device may further comprise a heater for the heat transfer cavity. The heater may be operated in the defrost mode so that any frost is melted more quickly. The heat exchanger may itself act as a heater, for example by driving the heat exchanger with a heated fluid rather than a coolant fluid. This may be done in a standard refrigeration circuit by bypassing hot refrigerant from the compressor past the condenser. In many parts of the world, mains power is not available or is subject to unexpected power cuts. If the power supply to a cooling device is suddenly interrupted then the heat transfer cavity will be left to warm up (or cool down) and an unhygienic pool of water is likely to collect inside. While a user may be alerted to manually open the outlet valve in such situations, this may not be acted upon. The Applicant has recognised that the outlet valve may instead be arranged to automatically drain liquid from the heat transfer cavity e.g. upon loss of electrical power to the heat exchanger. This is considered novel and inventive in its own right.
According to a fifth aspect of the present invention there is provided a heat transfer device comprising an electrically-powered heat exchange circuit, comprising a heat exchanger, a heat transfer cavity and a fan for creating a circulating gas flow between the heat exchanger and the heat transfer cavity, wherein the heat transfer cavity includes an outlet valve for exhausting gas and/or liquid, and wherein the outlet valve is automatically opened upon loss of electrical power to the heat exchange circuit.
Thus in the event that the heat exchanger and/or fan can no longer operate due to a loss of electrical power, the outlet valve is automatically opened so that liquid can drain from the heat transfer cavity as it warms up (or cools down). This means that user intervention is not required to ensure that the heat transfer cavity is kept dry and hygienic while the device is out of use. This aspect of the invention includes a method of drying a heat transfer device comprising a heat transfer cavity that can receive an object, the method comprising: creating a circulating gas flow in a heat transfer cavity that can receive an object; cooling or heating the circulating gas flow using an electrically-powered heat exchange circuit; opening an outlet valve to exhaust gas and/or liquid from the heat transfer cavity upon loss of electrical power to the heat exchange circuit. The method optionally further comprises: sensing loss of electrical power to the heat exchange circuit and actively opening the outlet valve.
In a set of embodiments the outlet valve may be biased open but held closed by an electromechanical actuator, for example an electromagnet or solenoid actuator. The electromechanical actuator may be connected to the heat exchange circuit so that, when electrical power is supplied to the circuit, the outlet valve is held closed. Upon loss of power the circuit is broken and the electromechanical actuator automatically released so that the valve is biased open. For example, the outlet valve may comprise an outlet opening and a spring-biased cover.
In another set of embodiments the outlet valve may be actively opened upon loss of electrical power. The device may include means for monitoring the power supply to the heat exchange circuit so as to detect when a power cut is happening, e.g. by detecting a drop in the power supply voltage. The device may comprise a controller that operates to open the outlet valve in response to a power cut detection signal. However, active opening of the outlet valve is likely to require electrical power, e.g. to drive an electromechanical actuator to uncover the outlet opening of the valve. In some examples the device may further comprise means for storing electrical power, such as a capacitor connected to the outlet valve. In some examples the device may further comprise means for generating electrical power, such as an electric brake arranged to convert the kinetic energy of a fan as it slows down upon power failure. In these embodiments the device can provide sufficient power to open the outlet valve when a power cut occurs.
In various embodiments of a heat transfer device as described above, the circulating gas flow between the heat exchanger and the heat transfer cavity is created by a fan, preferably an electric fan. The Applicant has found that the performance of an electric fan can be affected by electrostatic charge separation resulting from the phase changes occurring inside the heat transfer cavity. Especially where the heat transfer device is a cooling device, ice crystals that form in the cavity can be ingested by the fan. It is believed that electrostatic charge separation may be caused by dry ice crystals having piezoelectric properties. The circulating gas flow means that ice crystals can impact the fan at high velocity (e.g. 30-50 mph) and cause a build-up of charge that may result in arcing to the electrical components of the fan, for example causing a malfunction of the electric motor and/or control electronics. In order to mitigate this risk, charge build-up may be avoided by providing the fan with rotating components that are electrically insulated, e.g. formed of plastics material or metallic components having an insulating surface coating. A preferred solution is for the rotating components of the electric fan to be grounded. This is considered novel and inventive in its own right.
According to a sixth aspect of the present invention there is provided a heat transfer device comprising: a heat exchanger, a heat transfer cavity and an electric fan for creating a circulating gas flow between the heat exchanger and the heat transfer cavity; the electric fan comprising a rotating arrangement of vanes or blades mounted on a hub, and an electric motor driving the hub, wherein the rotating arrangement has an electrical connection to ground.
It will be appreciated that providing the rotating arrangement itself with an electrical connection to ground, in addition to any earthing of the drive motor, can ensure that static charge is not allowed to build up on the vanes/blades or hub. This can be particularly beneficial in examples where the rotating arrangement is mainly formed of metallic components, as is common. Such a rotating arrangement may be referred to as an impeller or rotor.
Preferably the heat transfer device is a cooling device. The earthing of the electric fan has been found effective in preventing charge build-up caused by ice crystals impacting on the rotating arrangement. In one set of examples the hub is mounted to the motor by bearings that establish the electrical connection to ground. Alternatively, a separate electrical connection may be provided. In various embodiments it is preferable for the electrical connection to ground to include an impedance, for example a resistor. This has been found to prevent or reduce EMC emission issues, if electrical noise is present, by reducing the ability of the fan (especially the motor hub) to act as an antenna.
Embodiments of this aspect of the invention may include any of the aforementioned features. For example, the device may comprise a controller arranged to operate the electric fan. The controller may adjust the rate of circulating gas flow created by the fan in response to one or more signals, e.g. a detection signal from a sensor when an object is inserted into the heat transfer cavity (rapid cooling/heating mode), or a defrost signal when the heat exchanger is turned off (defrost mode).
There will now be described some further features of a heat transfer device or cooling device in accordance with embodiments of any aspect of the invention.
While the device may be filled with a particular heat transfer gas, where the housing has an opening to allow an object to be inserted into the heat transfer cavity there is likely to be ingress of ambient air. Thus in preferred embodiments the circulating gas flow may be a circulating air flow. So as to help maintain the heat transfer cavity in a desired temperature range, and to avoid changes in moisture content, the opening is preferably arranged to minimise the entry of ambient air. It is preferable that there is only one opening into the heat transfer cavity while the heat exchanger is running. In addition, the opening may be partially or fully closed by a flexible membrane that is only pushed aside when an object is inserted through the opening. Keeping the opening closed when not in use helps pressures to equilibrate and prevents ambient air from being drawn into the cavity. In a set of embodiments the flexible membrane comprises a plurality of flaps extending inwardly from the housing and being deformable so as to define an aperture through the opening. For example, the flaps may be formed of a flexible polymeric or elastomeric material such as silicone. For a circular opening the flaps may extend radially inwardly. An advantage of such flap arrangements is that air may be encouraged to flow downwards through the aperture and down the sides of the object being inserted, so that any moisture carried by the air is deposited on surfaces of the object to create a frosted effect. Preferably the outer surface of the flaps provides a low coefficient of friction, especially in contact with glass, so that an object can be pushed through the aperture without gripping. For example, the flaps may be given a low friction coating e.g. of PTFE, or other low friction surface finish.
In the foregoing description it will be appreciated that what is meant by a circulating gas flow is a mass of gas that is entrained to flow continuously in a loop between the heat exchanger and the heat transfer cavity. During use of the device, and especially when an object is present in the cavity, the circulating gas flow may comprise a substantially constant mass of gas e.g. air trapped inside the heat transfer cavity. Of course, the volume of any mass of gas depends on its temperature. As mentioned above, air may enter and/or exit through the opening when an object is inserted therethrough, but preferably the opening is substantially closed at other times. The housing may also be designed to assist in keeping the heat transfer cavity cold and dry. In a set of embodiments the housing comprises a flange extending upwardly around the opening. This flange can trap a volume of drier air, which is denser than ambient air, directly above the opening. The height of such a flange is preferably at least 45 mm.
A heat transfer device according to any of the aspects or embodiments of the invention described above may comprise a heat exchanger comprising a Peltier element, for example providing a heating or cooling effect dependent on electrical current.
Additionally or alternatively, the heat transfer device may comprise a heat exchanger driven by movement of a coolant fluid therein, i.e. the heat transfer device may be a cooling device. The coolant fluid may be provided by an on-board refrigerant circuit. In addition, the heat exchanger may be part of an electrically-powered heat exchange circuit, and electrical power may be provided as part of the device. In other words, the cooling device may be a standalone unit. However, in various embodiments it is preferable for the cooling device to be compact so that it can easily be mounted on a bar, table or counter for use. In such embodiments there may be provided a two-part unit comprising the cooling device connected to a separate refrigerant device. The refrigerant device may provide the coolant fluid and/or electrical power. For example, the refrigerant device may comprise one or more of: an electrical power supply; a refrigerant circuit; and a controller for the refrigerant circuit. The refrigerant circuit may include a condenser and a pump for the coolant fluid.
A typical refrigerant circuit may comprise a compressor to pressurise the coolant fluid returning from the cooling device, a condenser to remove heat from the fluid, and an expansion device to rapidly cool the fluid before it is supplied to the cooling device. The expansion device may comprise a thermostatic expansion valve or a capillary tube. When the expansion device is located in the refrigerant device, cold fluid travels to the cooling device and warm fluid returns to the refrigerant device. It is not ideal for such two-way fluid communication to be carried by the same fluid line as the returning warm fluid then tends to raise the temperature of the cold fluid before it reaches the cooling device and/or because relatively thick insulation may be required. The Applicant has recognised that cooling efficiency can be improved by separating the expansion device from the rest of the refrigerant circuit and locating the expansion device in the cooling device instead of the refrigerant device. This is considered novel and inventive in its own right.
Thus according to a further aspect of the present invention there is provided a two-part cooling apparatus comprising a cooling device connected to a separate refrigerant device, wherein the refrigerant device includes a compressor and a condenser for coolant fluid supplied to/from the cooling device, and wherein the cooling device includes an expansion valve. This means that the coolant fluid is still warm when it is transferred from the refrigerant device to the cooling device. The connection preferably provides for two-way transfer of coolant fluid between the refrigerant device and the cooling device. The coolant fluid travelling to the cooling device can advantageously transfer some of its heat to the returning fluid as they pass through the shared connection. This can improve the efficiency of the overall refrigerant circuit by lowering the temperature of the coolant fluid before it reaches the expansion valve. Furthermore, pre-heating the coolant fluid before it reaches the refrigerant device can ensure that liquid is not returned to the compressor, e.g. due to very cold temperatures in the cooling device due to non-use, protecting the compressor from damage. For example, the cooling device may be connected to the separate refrigerant device by an umbilical cord or flexible line that carries the coolant fluid. A higher average temperature in the umbilical cord can reduce its insulation requirements, especially when the apparatus is in a relatively warm ambient environment. As is discussed above, the refrigerant circuit may be controlled to adjust the speed and/or temperature of the coolant fluid that is provided to the cooling device e.g. to drive the heat exchanger at a different heat transfer rate and switch between peak/off-peak modes of operation. It is therefore preferable that the controller for the refrigerant circuit is in communication with any controller in the cooling device. Detection signals from sensors in the cooling device, for example an object detection sensor and/or temperature sensor, can then be passed from the controller for the cooling device to the controller for the refrigerant circuit as necessary. Such communication of control signals may be combined with electrical power being supplied from the refrigerant device to the cooling device. A two-way electrical cable may be connected between the refrigerant device and the cooling device. The electrical connection(s) between the refrigerant device and the cooling device may be separate from refrigerant lines supplying the coolant fluid to/from the two devices. However, in a preferred set of embodiments the two-part unit comprises a cooling device connected to a separate refrigerant device by an umbilical cord or flexible line that also provides an electrical connection e.g. both electrical connection and transfer of a coolant fluid.
The umbilical cord provides a tidy way to connect the cooling device to a separate refrigerant device. The two devices may be permanently connected by the umbilical cord. However, in at least some embodiment, the umbilical cord includes a separable connection. This means that the cooling device can be installed separately from the refrigerant device, and different devices may be connected together. For example, in a bar environment, a refrigerant device may be installed more permanently out of view of customers while one or more bar-top cooling device may be temporarily installed and connected to the refrigerant device when required. The separable connection may include a seal for the coolant fluid, to allow for separation without leakage. So-called “quick disconnect” couplings may be used. In at least some embodiments, the separable connection may be poka-yoke i.e. designed so that it can only be connected the right way round.
To improve flexibility in the positioning of the cooling device relative to the refrigerant device, and in routing of the umbilical, the umbilical cord is preferably connected to the refrigerant device at an angle of around 45°. This means that it can readily be bent to extend either horizontally or vertically towards the cooling device. In various examples, the umbilical cord may be at least 50 cm, 60 cm, 70 cm, 80 cm, 90 cm or 1 m long. Preferably the umbilical cord is at least 2 m, 3 m, 4 m, or 5 m long. The umbilical cord may be up to about 10 m long.

Some embodiments of the present invention will now be described, by way of example only, and with reference to the accompanying figures, in which:

FIG. 1ais a cross-sectional view of a cooling device andFIG. 1bis a schematic illustration of the circulating airflow in such a device;

FIG. 2ais a top view of a sensor arrangement across the opening of such a cooling device and

FIG. 2bis a side cross-sectional view of the opening;

FIG. 3aandFIG. 3bshow an infrared sensor arrangement to detect when a glass is inserted through the opening;

FIG. 4 shows a black and white image of passive thermal emission in the far infrared spectrum for a glass inserted through the opening;

FIG. 5aandFIG. 5bprovide a side sectional view and a perspective sectional view of a capacitive sensor arrangement;

FIG. 6 is a side sectional view of a cooling device including an electrical connection to earth;

FIG. 7 is a schematic side sectional view of a cooling device including an outlet valve;

FIG. 8 is a top view of an outlet flow path in the base of the heat transfer cavity of a cooling device;

FIGS. 9a-9cprovide perspective and side sectional views of the outlet valve in the base of a heat transfer cavity;

FIG. 10 is a side sectional view of a counter-top cooling device;

FIGS. 11aand 11bprovide schematic side views of a counter-top cooling device connected to a refrigerant device by an umbilical cord; and

FIG. 12 provides a schematic overview of the components in a cooling device connected to a separate refrigerant device.

There is seen inFIG. 1aanexemplary cooling device2 that may be used to chill and frost abeer glass4 inserted into aheat transfer cavity6 of thedevice2. Theheat transfer cavity6 is defined by a double-walled,cylindrical ducting member8 that is shaped to receive aninverted beer glass4. Theducting member8 may be removable and optionally interchangeable, for example to allow for different sizes and shapes ofbeer glass4 to be positioned in theheat transfer cavity6. Surrounding theducting member8 is aheat exchanger10 in the form of a set of coils. In this example, theheat exchanger10 is a heat sink comprising multiple copper coils that are cooled by a refrigerant fluid pumped there through. Afan12 is positioned below theducting member8 andheat exchanger10 so as to create a circulating airflow in theheat transfer cavity6. The schematic inset ofFIG. 1billustrates how air, or any other gas insideheat transfer cavity6, is circulated by thefan12. As is described in WO 2011/042698, theducting member8 is shaped as a pseudo-negative of theglass4 to be cooled such that there is a specified gap between theducting8 and theglass4 that promotes turbulence in the airflow. When thefan12 is operated at high speed, the circulating airflow is highly turbulent and this generates a high heat transfer coefficient so as to achieve rapid cooling. As seen inFIG. 1b, the airflow is drawn out of theheat transfer cavity6 by thefan12 at (1), driven across the coils of theheat exchanger10 at (2) and circulated around theducting member8 at (3), with a restricted region between theglass4 and theducting member8 acting to accelerate the airflow and create turbulence for optimal heat transfer with the glass at (4).

Thecooling device2 includes an outer housing defining anopening14 that allows theglass4 or other object to be inserted into theheat transfer cavity6. Theopening14 may be closed by aflexible membrane16 or other seal so as to help retain the cold air inside theheat transfer cavity6. The housing provides aflange17 extending circumferentially around theopening14 and extending for a height above the opening. It has been found beneficial to make the flange at least 45 mm high. This helps to trap a static volume of air above theopening14, which may be cooler than ambient and hence denser. Theflange17 surrounds the protruding base of aglass4 while it is being frosted.

Various embodiments of such a cooling device will now be described with reference to the subsequent figures. Although the object inserted into the heat transfer cavity is described as a glass, it will be appreciated that other objects may of course be cooled instead. Furthermore, the heat exchanger may take the form of a thermal sink or thermal source and, in the latter case, the heat transfer cavity may be arranged to warm rather than cool an object inserted therein.

There is seen inFIGS. 2-5 some non-contact sensor arrangements for detecting when a glass is inserted into the heat transfer cavity of a cooling device. In the example ofFIGS. 2aand 2b, an active radiation sensor arrangement is used to detect when aglass4 is inserted through anopening14 in the upper part of theheat transfer cavity6. It may be seen with reference toFIG. 1athat theopening14 is generally closed by aflexible membrane16 that can be deformed so as to allow aglass4 to be pushed through theopening14 and down into theheat transfer cavity6. The top view ofFIG. 2ashows aflexible membrane16 that is split into radial flaps providing a flexible seal around theglass4. The flaps bend against theglass4 when it is inserted, to provide an intimate seal and encouraging any air that is pulled into theheat transfer cavity6 to curve down the sides of theglass4. Once positioned in theheat transfer cavity6, an upper end of theglass4 protrudes above theopening14 so as to enable the user to grip the glass when it is ready to be removed. The protruding base of theglass4 is detected by a light gate arrangement indicated generally by18 inFIGS. 2aand 2b. Thelight gate18 is defined between an infrared light emitting diode (LED)20 and aphotodiode22 arranged non-diametrically opposite theLED20. TheLED emitter20 andphotodiode receiver22 may be filtered so as to be sensitive to the same wavelength range.

It can be seen fromFIGS. 2aand 2bthat the emitter/

ray receiver pair

20,22 andlight gate18 therebetween is offset by adistance24 to one side of the centre of theglass4, e.g. offset by 10 mm. The emitter/

receiver pair

20,22 is positioned so that thelight gate18 is at the same height as the thickened base of theglass4.Lenses26 that are clear to infrared light can be used to hide theemitter20 andreceiver22 and protect them from frost growth. For each sensor reading, a controller turns theLED emitter20 on and off 50 times and converts a detection signal from thereceiver22 at each step by a 10-bit ADC to eliminate ambient infrared from the reading. The on and off values are summed separately, and the off total is subtracted from the on total. It has been found that such an infrared sensor arrangement works best with a narrow beam LED with a half angle of 20° or less. For example, theemitter20 may be an 8° half angle LED, for which typical sensor reading values are 3,000-4,000 without a glass present and 200-300 with a glass present, giving at least a 10:1 ratio, which allows a simple threshold for the detection signal to determine whether aglass4 is present or not.

Another non-contact sensor arrangement is seen inFIGS. 3 and 4. This arrangement uses passive thermal emission in the far infrared spectrum to detect anambient temperature glass4 that is inserted through an aperture defined by theflexible membrane16. As seen inFIGS. 3aand 3b, a far-infrared (FIR)thermopile sensor28 is positioned to point down at an angle through the opening to the cold heat transfer cavity inside the device. The field ofview30 of thesensor28 includes the lesscold aperture seal16 as well as the aperture itself. When aglass4 is inserted (FIG. 3b), much of the field ofview30 is filled by the base of theglass4, which is at ambient temperature. The thermal emission image shown inFIG. 4 shows that theambient temperature glass4 is clearly visible against the cold aperture andaperture seal16. While typical temperatures sensed for the aperture may be −15° to −35°, theambient temperature glass4 gives about 40° C. swing in reading.

Another non-contact sensor arrangement is seen inFIGS. 5aand 5b. In this example the presence of aglass4 in theheat transfer cavity6 is detected by measuring changes in capacitance. Glass in particular provides for good detectability in air because it has a relative permittivity of between around 4 and 10. In this capacitive sensor arrangement,

electrodes

32,34 are arranged in theheat transfer cavity6 on either side of theducting member8, so that aninner electrode32 is positioned inside the insertedglass4 and anouter electrode34 is positioned outside theglass4. To eliminate sensitivity to local ice build-up and improve glass protection capability, concentric annular (e.g. cylindrical/frustoconical)

electrodes

32,34 are used to increase surface area. Such an arrangement is less proximity-dependent so that the build-up of a thin ice or frost layer on the surfaces of theglass4 does not affect sensor readings. It has been found that good glass detection sensitivity can be achieved with an electrode separation of several centimetres, even with two layers ofplastic ducting member8 in series. The

electrodes

32,34 may be provided as annular plates, or may take the form of conductive coatings applied to theplastic ducting member8 or other suitable surfaces inside the housing of thedevice2. Conductive paint (such as that used for EMC shielding), printed conductive tracks and chromed finishes are all appropriate methods of achieving sufficiently

effective electrodes

32,34. If theducting member8 carried the

electrodes

32,34 and it is removable, then a separable electrical connection may be required. As is seen most clearly fromFIG. 5b, theducting member8 may be removably positioned over aninner moulding36 that carries the

capacitive sensing electrodes

32,34. Theinner moulding36 may be permanently positioned inside the device housing. Theinner moulding36 includes aninner tube38 that runs up the inside of theducting member8 to prevent fingers from reaching the fan (not shown) when theducting member8 is removed. Theinner tube38 is an ideal part to apply a coating for theinner electrode32 so that it penetrates deep inside theglass4 without any need for an electrical connection to theducting member8. Theouter electrode34 may be fitted inside themoulding36, or alternatively a coating can be applied to an inner surface of thecylindrical moulding36.

FIG. 6 provides a side sectional view similar to that seen inFIG. 1a, except that details of thefan12 are visible. It can be seen that theelectric fan12 comprises a rotating arrangement of vanes or blades mounted on ahub40. Thehub40 is driven by arotating drive shaft42 withbearings44 arranged therebetween. Theshaft42 extends from afan base46 that has an electrical connection to ground48. Animpedance50 may optionally be added to the grounding line so as to prevent any EMC emissions if electrical noise is present, by reducing the ability of thehub40 to act as an antenna. It has been found that there may be sufficient electrical conduction through thebearings44 that connect thefan base46 to thehub40, but other connection methods are also possible. Earthing of thefan hub40 means that a metallic hub can be used instead of a plastic hub. It has been found that when ice crystals are ingested into thefan12 it can cause a malfunction. This is often only momentary, but occasionally terminal for the fan motor and its control board. The cause of this malfunction is believed to be electrostatic charge separation seemingly caused by the high velocity (e.g. 30-50 mph) impact of ice crystals onto thefan hub40, as generally indicated by the arrows inFIG. 6. It seems that sufficient charge may build up on thehub40 to cause an electrical arc to the fan motor or drive electronics below, affecting operation of the fan controller.

Any of the non-contact sensor arrangements described above may be used, alone or in combination, to detect when an object such as a glass is inserted into the heat transfer cavity of a cooling device. A controller connected to the fan may then adjust the rate of circulating airflow in response to a detection signal from the sensor arrangement. Insertion of a glass or other object may trigger a rapid cooling mode in which the fan speed is increased. Readings from the sensor arrangement may also be used by the controller to decide when to switch the cooling device between peak and off-peak modes of operation, for example when it is determined that the cooling device has not been used for a certain period of time.

In addition to the modes of operation mentioned above, the cooling device may be operated in a defrost mode where theheat exchanger10 is turned off and theheat transfer cavity6 is allowed to defrost. As in seen in the schematic ofFIG. 7, theheat transfer cavity6 may be provided with anoutlet valve52 that enables fluid to leave theheat transfer cavity6, for example to drain water produced during defrost. During a defrost mode of operation, the flow of refrigerant through theheat exchanger10 may be stopped so that the coils begin to warm up under the thermal load. Thefan12 may be turned on to full power so as to circulate the air as it warms up and assist in drying out theheat transfer cavity6. When the defrost mode is activated, theoutlet valve52 may be opened so that air is pulled through theheat exchange cavity6 and liquid can drain out. As indicated byarrow54, ambient air may be drawn in through theupper opening14 and the circulating air movement helps to exchange heat and moisture with the outside world through the ventingflow55 provided by theoutlet valve52. The high air speed created by thefan12 can act to quickly clear droplets of water created from condensation and melted frost. In addition, the increase in power dissipated by thefan12 can help to warm up the inside of thecooling device2, helping to melt and evaporate frost and increasing the capacity of the airflow to carry water vapour. Thefan12 may include potted or coated electronics so as to be unaffected by moisture ingress.

The flow path to theoutlet vent52 and its position will now be described in more detail with reference toFIGS. 8 and 9. As seen from the top view ofFIG. 8, the heat transfer cavity includes anexit56 to theoutlet valve52 is at a point near the periphery of thefan12. The flow path indicated by thearrows60 is arranged to run towards theexit56 tangential to the direction ofrotation58 of thefan12. This point in the air circuit is at relatively high pressure, whereas theopening14 is at relatively low pressure, and so ambient air is drawn in through the top of theheat transfer cavity6 and ejected through theoutlet vent52. The position of theexit56, outside thefan12 and angled tangentially, not only benefits the air pressure recovery—encouraging good flow—but also allows spray that is flung tangentially from thefan12 to be collected effectively. Furthermore, the floor of theheat transfer cavity6 around thefan12 may slope downwards towards theexit56 in the general direction of air flow, allowing water collected in the bottom of thecavity6 to drain out through thevent52. Thearrows60 inFIG. 8 indicate how the floor of theheat transfer cavity6 slopes continually downwards towards theexit56. Furthermore, the

arrows

62 and64 indicate how the floor of theheat transfer cavity6 may be inclined in a radial direction, on both sides, so that liquid runs down onto theoutlet flow path60, which is then sloped downwardly in a circumferential direction towards theexit56. In other words, the base of theheat transfer cavity6 may be designed to provide a helical flow path that collects and drains liquid towards theexit56.

Theoutlet valve52 is seen in more detail inFIGS. 9a-9c. Theoutlet valve52 comprises anoutlet opening66 leading out horizontally from theexit56. Amovable cover68 is operated by aservo motor70. Theopening66 is positioned above afunnel72 designed to catch droplets of liquid as they drip out of theopening66, which is provided with apointed protrusion74 that encourages any droplets remaining attached to collect directly into thefunnel72. Thefunnel72 narrows to anexit tube76 which is designed not to restrict airflow out of thevalve52 by having internal dimensions of 12.5 mm by 9 mm (95.1 mm²). Thetube76 passes through the bottom of the housing of thecooling device2 so as to direct liquid into anexternal drip tray78. As is seen in the cross-sectional view ofFIG. 9b, theexit tube76 has apointed end80 to clear drips more effectively. Melt water collected in thedrip tray78 can be left to evaporate or may be emptied out. Thedrip tray78 may be removable for this purpose. It has been found that theexit opening66 should ideally provide an unrestricted airflow path to promote circulation and dry out the heat transfer cavity quickly. For acceptable defrosting times, e.g. about 20 minutes (depending on ambient conditions), theexit56 and flow path to theopening66 may be made larger than 50 mm²in cross-section along its length. The entire exit path may be more than 300 mm²to provide for effective drying in a relatively short time period. Theopening66 may be a tube having an internal diameter of about 18.5 mm. From the cross-sectional view ofFIG. 9cit can be seen how theopening66 is at the end of a tube that extends generally horizontally through the housing from a periphery of thefan12. Furthermore, comparing the left and right sides inFIG. 9c, it can be seen that thebase7 of the heat transfer cavity starts higher on the left side and then spirals downwardly, around the outside of thefan12, to reach a low point at theexit56 to theoutlet opening66.

Theservo motor7 operates to open theoutlet valve52 whenever thecooling device2 enters a defrost mode. In addition, thedevice2 may be designed to automatically enter a defrost mode in the event of a power cut. It is important that the glass froster i.e. coolingdevice2 is able to drain if affected by a power cut, to avoid an unhygienic pool of water being trapped in the bottom of the device as it warms up. While it is not possible to operate thefan12 to assist in defrosting without power, sufficient energy can be stored to open theoutlet vent52 just as the power is cut off, at least enabling the unit to drain. The controller may include an extra capacitance to store energy powering the logic andservo motor70, as well as means of detecting a drop in the supply voltage. In an alternative system, the motor of thefan12 may be turned into a generator by electric braking, thereby converting the remaining kinetic energy of the spinning fan into power to operate themotor70 and open thevent52. In some examples, theservo motor70 may be replaced by a solenoid actuator with thecover68 being sprung open but held closed by an electromagnet, such that when necessary, or when the power supply is cut, the electromagnet releases the spring and thecover68 is opened.

FIG. 10 shows thecooling device2 in the form of a countertop or bar top unit including an on-board controller82 and aclamp84 to mount the unit to a counter surface. Anumbilical cord86 is used to transfer refrigerant fluid and power to thecooling device2.FIGS. 11aand 11billustrate how theumbilical cord86 may be connected to a separaterefrigerant device88 at 45 degrees, such that it can be bent either to lead vertically upwards or horizontally. Areversible cover plate90 can then be attached in one of two orientations, depending on the direction ofumbilical cord86 that is required to fit different countertop arrangements.

Finally, it is seen with reference toFIG. 12 how theumbilical cord86 may transfer coolant fluid e.g. refrigerant between therefrigerant device88 and the bartop cooling device2, as well as relayingcontrol signals92 and providing anelectrical power supply94. Thecooler device2 includes heat exchanger coils10,fan12, defrostvalve56, controller (e.g. PCB)82,temperature sensor96,glass detection sensor98,display100 andcontrol interface102. Therefrigerant device88 includes amains power cable104, a DC power supply106 for thecooling device2, afridge control relay108 and acondensing unit110. Signals from thecontroller82 in thecooling device2 may be transmitted to thefridge control relay108 so as to determine when the apparatus is operating in peak or off-peak mode. Any suitable coolant fluid may be used, for example a refrigerant such as R404A.

In peak mode, the condensingunit110 may be constantly running and thesensor96 used to monitor the temperature inside thecooling device2 so as to maintain the heat transfer cavity in a desired temperature range e.g. −35° C. to −45° C. In off-peak mode, the heat transfer cavity may be maintained at a higher temperature by turning off the condensingunit110 for some of the time, e.g. maintaining the cooling device in the temperature range of −25° C. to −35° C. Periodically turning off the condensingunit110 results in a lower average heat transfer rate in the off-peak mode. The compressor in atypical condensing unit110 cannot be turned back on for one minute (or more) after being turned off due to the back pressure, meaning there could be a significant rise in internal temperature of thecooling device2. This would affect peak throughput, as the extra load of cooling glasses would worsen the rise while the compressor needs to stay off. In the off-peak mode, however, by not needing to frost a glass as quickly, such a temperature rise would be acceptable, so cycling the fridge compressor on and off is an effective way of lowering the power consumption significantly.

The higher internal temperature in the off-peak mode may be compensated by an increase in the time spent frosting a glass, which would be less significant to performance during off-peak times of use. The

controllers

82,108 may respond to glass detection signals from thesensor98 to provide a faster cool down reaction to increased loads, e.g. frosting of multiple glasses in a series. This may be in addition to thecontroller82 increasing the speed of thefan12 when theglass sensor98 provides a detection signal that causes thecooling device2 to switch into rapid cooling mode. The system may include a time delay before switching into off-peak mode, to avoid cycling the condensing unit110 (especially the compressor) too often, to prevent damage or excessive wear. If the condensingunit110 was turned off more than e.g. two minutes ago, then inserting a glass may make it turn back on automatically. When responding to an inserted glass in off-peak mode, the rate at which the internal thermal mass warms will increase under the load of frosting a glass, but there will be a delay before this is detected by temperature measurement. Therefore turning on thecondensing unit110 when the glass is inserted can improve performance.

Thefridge condensing unit110 in therefrigerant device88 may include, as is conventional, a compressor to pressurise the coolant fluid e.g. refrigerant returning from thecooling device2, a condenser to remove heat from the fluid, and an expansion device to rapidly cool the fluid before it is supplied back to thecooling device2. However, there is envisaged an embodiment in which the expansion valve is instead provided within thecooling device2, so that warmer refrigerant is transferred from therefrigerant device88 to thecooling device2 via theumbilical cord86. Theumbilical cord86 may then allow for energy regeneration, hot refrigerant flowing out transferring heat to the cold refrigerant returning. Additionally, the higher average temperature in theumbilical cord86 may mean reduced heat gain through its insulation or even a reduced thickness of insulation required. Theumbilical cord86 may be a flexible tube containing cables to transfer power and control, and hoses to transfer refrigerant fluid between therefrigerant device88 and the bartop glass froster2. Theumbilical cord86 may have a quick disconnect on the hoses, as well as a separable electrical connector. This may make installation considerably easier, as the two parts of the system can be installed separately. To ensure correct connection, these connectors may be designed poka-yoke by having one female and one male connector on the umbilical and one of each to match on therefrigerant device88, such that they cannot be connected the wrong way round.

Claims

1. A heat transfer device comprising:

a heat exchanger driven by movement of a fluid therein, a heat transfer cavity and a fan for creating a circulating gas flow between the heat exchanger and the heat transfer cavity;

a housing having an opening for allowing an object to be inserted into the heat transfer cavity;

an outlet valve for exhausting gas and/or liquid from the heat transfer cavity; and

a controller arranged to operate the outlet valve.

2. A heat transfer device according toclaim 1, wherein the heat transfer cavity comprises an outlet flow path arranged to direct liquid towards the outlet valve.

3. A heat transfer device comprising:

a heat exchanger, a heat transfer cavity and means for creating a circulating gas flow between the heat exchanger and the heat transfer cavity;

a housing having an opening for allowing an object to be inserted into the heat transfer cavity; and

an outlet valve for exhausting gas and/or liquid from the heat transfer cavity;

wherein the heat transfer cavity comprises an outlet flow path arranged to direct liquid towards the outlet valve.

4. A heat transfer device according toclaim 2, wherein the outlet flow path is inclined downwardly in a radial and/or circumferential direction so as to direct liquid towards the outlet valve.

5. A heat transfer device according toclaim 2, wherein the outlet flow path provides a helical incline towards the outlet valve.

6. A heat transfer device according toclaim 1, wherein the outlet valve comprises an outlet opening that is directed substantially tangential to the direction of the circulating gas flow.

7. A heat transfer device according toclaim 6, wherein the outlet opening is substantially positioned at a periphery of the fan.

8. A heat transfer device according toclaim 1, wherein the outlet valve comprises an outlet opening having a cross-sectional area of at least about 50 mm².

9. A heat transfer device according toclaim 1, further comprising a funnel arranged adjacent to the outlet valve to collect liquid.

10. A heat transfer device according toclaim 1, wherein the heat transfer device is a cooling device and the heat exchanger is a thermal sink arranged to cool the circulating gas flow.

11. A heat transfer device according toclaim 1, wherein the controller is further arranged to control the fan.

12. A heat transfer device according toclaim 1, wherein in a (“defrost”) mode of operation the heat exchanger is no longer driven and the controller opens the outlet valve.

13. A heat transfer device according toclaim 12, wherein in the (“defrost”) mode of operation the controller operates the fan at an increased speed so as to circulate the gas flow more rapidly.

14. A heat transfer device according toclaim 12, further comprising a heater operating in the (“defrost”) mode of operation, and optionally wherein the heat exchanger acts as the heater.

15. (canceled)

16. A heat transfer device according toclaim 1, wherein the outlet valve is arranged to automatically drain liquid from the heat transfer cavity upon loss of electrical power to the heat exchanger, or the controller operates to open the outlet valve in response to a power cut detection signal.

17. (canceled)

18. A heat transfer device according toclaim 1, wherein the outlet valve is biased open but held closed by an electromechanical actuator.

19. A heat transfer device according toclaim 1, wherein the outlet valve is actively opened upon loss of electrical power.

20. (canceled)

21. A heat transfer device according toclaim 1, comprising means for storing electrical power and/or means for generating electrical power so that the outlet valve can be opened in response to a power cut.

68. A method of drying a heat transfer device comprising a heat transfer cavity that can receive an object, the method comprising:

creating a circulating gas flow in the heat transfer cavity;

ceasing to cool or heat the circulating gas flow; and

opening an outlet valve to exhaust gas and/or liquid from the heat transfer cavity.

69. A method according toclaim 68, further comprising:

increasing the rate of the circulating gas flow.

70. (canceled)

71. (canceled)