US20100095704A1

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Info

Publication number: US20100095704A1
Application number: US12/644,726
Authority: US
Inventors: Kirill Ignatiev; Jean-Luc M. Caillat
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-10-02
Filing date: 2009-12-22
Publication date: 2010-04-22
Also published as: US20080078192A1; US7647790B2

Abstract

A refrigeration system can incorporate a cooling-liquid injection system that can inject a cooling liquid into an intermediate-pressure location of the compressor. The cooling liquid can absorb the heat of compression during the compression of the refrigerant flowing therethrough. The refrigeration system can include an economizer system that injects a refrigerant vapor into an intermediate-pressure location of the compressor in conjunction with the injection of the cooling liquid. A refrigeration system can include a liquid-refrigerant injection system that can inject liquid refrigerant into an intermediate-pressure location of the compressor. The injected liquid refrigerant can reduce the discharge temperature of the refrigerant. The liquid-refrigerant injection system can be used with the cooling-liquid injection system and/or the economizer system.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 11/707,628 filed on Feb. 19, 2007, which is a continuation-in-part of U.S. patent application Ser. No. 11/541,951 filed on Oct. 2, 2006, and which claims the benefit of U.S. Provisional Application No. 60/880,698 filed on Jan. 16, 2007. The disclosures of the above applications are incorporated herein by reference.

FIELD

The present teachings relate generally to refrigeration and, more particularly, to injection systems and methods for refrigeration compressors.

BACKGROUND AND SUMMARY

The statements in this section merely provide background information related to the present teachings and may not constitute prior art.

Compressors are utilized to compress refrigerant for refrigeration systems, such as air conditioning, refrigeration, etc. During the compression of the refrigerant within the compressor, a significant quantity of heat can be generated, which may result in the temperature of the discharged refrigerant being relatively high. A reduction in the discharge temperature of the refrigerant can increase the cooling capacity and efficiency of the refrigeration system.

A refrigeration system according to the present teachings may incorporate a liquid-refrigerant injection system that can provide liquid refrigerant to an intermediate-pressure location of the compressor and absorb heat during compression of the refrigerant flowing therethrough. The injected liquid refrigerant may decrease the temperature of the compression process and the temperature of the refrigerant discharged from the compressor.

A refrigeration system according to the present teachings may also include a single-phase cooling-liquid injection system that provides a single-phase cooling liquid to an intermediate-pressure location of the compressor and absorbs heat during the compression of the refrigerant flowing therethrough. The cooling liquid, which may be externally separated from the refrigerant flow, may decrease the temperature of the refrigerant being discharged by the compressor, resulting in an increased cooling capacity and/or an increased efficiency. Use of the cooling-liquid injection system in conjunction with the liquid-refrigerant injection system may further increase cooling capacity and/or increase efficiency of the compressor.

A refrigeration system according to the present teachings may also include an economizer system that provides a vapor refrigerant to an intermediate-pressure location of the compressor and may reduce the operational temperature of refrigerant prior to flowing through an evaporator, thereby increasing the cooling capacity. Use of the economizer system in conjunction with the liquid-refrigerant injection system and/or the cooling-liquid injection system may further increase the cooling capacity, efficiency, and/or performance of the compressor.

Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present claims.

DRAWINGS

The drawings described herein are for illustration purposes only and are not intended to limit the present teachings in any way.

FIG. 1 is a schematic view of a refrigeration system according to the present teachings;

FIG. 2 is a schematic view of another refrigeration system according to the present teachings;

FIG. 3 is a schematic view of yet another refrigeration system according to the present teachings;

FIG. 4 is a schematic view of still another refrigeration system according to the present teachings;

FIG. 5 is a schematic view of an alternate fluid-injection mechanization according to the present teachings;

FIG. 6 is a schematic view of yet another alternate fluid-injection mechanization according to the present teachings;

FIG. 7 is a cross-sectional view of a scroll compressor suitable for use in refrigeration systems according to the present teachings;

FIG. 8 is an enlarged fragmented cross-sectional view of a portion of the compressor ofFIG. 7 showing the scroll members;

FIG. 9 is a top-plan view of fixed scroll member of the compressor ofFIG. 7;

FIG. 10 is a fragmented cross-sectional view of a two-stage rotary compressor suitable for use in the refrigeration systems according to the present teachings;

FIG. 11 is a fragmented cross-sectional view of a portion of a screw compressor suitable for use in the refrigeration systems according to the present teachings;

FIG. 12 is a schematic view of a compressor with an integral liquid/gas separator suitable for use in the refrigeration systems according to the present teachings; and

FIG. 13 is a schematic view of a compressor with an internal liquid/gas separator and an integral cooling-liquid heat exchanger and gas cooler suitable for use in the refrigeration systems according to the present teachings.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals (e.g., 20, 120, 220, 320 and 30, 130, 230, 330, etc.) indicate like or corresponding parts and features.

Referring toFIG. 1, arefrigeration system20 according to the present teachings is shown.Refrigeration system20 is a vapor-compression refrigeration system that may be configured for a trans-critical refrigeration cycle wherein the refrigerant is at a pressure above its critical pressure during a part of the cycle, thus being in the gaseous form regardless of the temperature, and is below its critical pressure in the other parts of the cycle, thereby enabling the refrigerant to be in vapor or liquid form. The refrigerant can be carbon dioxide (CO₂) and other refrigerants. The system may also be used at non-trans-critical operating conditions.

Refrigeration system

20 includes acompressor22 that compresses refrigerant flowing therethrough from a suction pressure to a discharge pressure. Whenrefrigeration system20 is a trans-critical refrigeration cycle, the suction pressure is less than the critical pressure of the refrigerant while the discharge pressure is greater than the critical pressure of the refrigerant.Compressor22 may be a single-stage positive displacement compressor, such as a scroll compressor. Alternatively, other positive displacement-type compressors may be used, such as screw compressors, two-stage rotary compressors, and two-stage reciprocating piston compressors.

Compressor

22 includes an inlet/suction port24 in communication with asuction line26 to supply refrigerant to the suction or low-pressure side ofcompressor22.Compressor22 includes an outlet/discharge port28 in communication with adischarge line30 that receives compressed refrigerant from the discharge chamber ofcompressor22.Compressor22 may include an intermediate-pressure port32 that communicates with the compression cavities ofcompressor22 at a location that corresponds to an intermediate pressure between the discharge pressure and the suction pressure. Intermediate-pressure port32 supplies a fluid to the compression cavities ofcompressor22 at an intermediate-pressure location.

Inrefrigeration system20, a cooling-liquid injection system33 is used to inject a cooling liquid into the compression cavities at an intermediate-pressure location through intermediate-pressure port32, as described below. The cooling liquid, which is in a single-phase liquid state throughout the refrigeration cycle, may be a lubricant or oil, such as different types of mineral oil, or synthetic oils like, but not limited to, polyolester (POE), polyalkyleneglycol (PAG), alkylbenzene, polyalfaolefin (PAO) oils. In certain conditions other fluids, like water or mercury, may be used.

Discharge line

30 communicates with a gas/liquid separator38.Discharge line30 may route the high-temperature, high-pressure fluid discharged bycompressor22 directly fromdischarge port28 toseparator38. The fluid discharged fromcompressor22 includes both refrigerant, in gaseous form, and the injected cooling liquid.Separator38, which may be approximately at the discharge pressure and temperature ofcompressor22, receives discharged refrigerant above the critical pressure and in gaseous form regardless of the temperature withinseparator38. The cooling liquid, however, maintains a single-phase form throughout the refrigeration cycle. Withinseparator38, the refrigerant is separated from the cooling liquid which is utilized to cool the compressing process and absorb the heat of compression associated withcompressor22 compressing the refrigerant flowing therethrough.

The cooling-liquid injection system33 may include a high-temperature cooling-liquid line40, aheat exchanger42, a fan orblower44, a low-temperature cooling-liquid line46, a throttle/expansion device48, and aninjection line50. The separated high-temperature cooling liquid flows fromseparator38 through high-temperature cooling-liquid line40 and intoheat exchanger42. Withinheat exchanger42, heat Q₁is extracted from the cooling liquid and transferred to ambient. Fan orblower44 can facilitate the heat transfer by flowing ambient air acrossheat exchanger42 in heat-conducting relation with the cooling liquid flowing therethrough. Alternatively,heat exchanger42 may be a liquid-liquid heat exchanger, such as whenrefrigeration system20 is used as a heat pump system, wherein the heat Q₁can be used to heat water flowing through the heat pump system.

The cooling liquid exitsheat exchanger42 as a high-pressure, low-temperature liquid through low-temperature cooling-liquid line46.Throttle device48 interconnects low-temperature cooling-liquid line46 withinjection line50. The reduced-pressure cooling liquid flows fromthrottle device48 to intermediate-pressure port32 through aninjection line50 for injection into the compression cavities that communicate with intermediate-pressure port32. The cooling liquid is injected intocompressor22 to extract the heat created by compressing the refrigerant flowing therethrough. The heat can be discharged to the ambient as heat Q₁byheat exchanger42.Throttle device48 controls the flow therethrough and reduces the pressure of the cooling liquid to a pressure less than the discharge pressure but greater than the intermediate pressure of the compression cavities that communicate with intermediate-pressure port32.Throttle device48, which may take a variety of forms, may be dynamic, static, or quasi-static. For example,throttle device48 may be an adjustable valve, a fixed orifice, a pressure regulator, or the like. When dynamic,throttle device48 may vary the amount of cooling liquid flowing therethrough and injected intocompressor22 through intermediate-pressure port32 based on operation ofrefrigeration system20, operation ofcompressor22, to achieve desired operation ofrefrigeration system20, and/or to achieve a desired operation ofcompressor22. By way of non-limiting example,throttle device48 may adjust the flow of cooling liquid therethrough to achieve a desired discharge temperature of the refrigerant exitingdischarge port28.

For temperature-based regulation of the cooling liquid flowing throughthrottle device48, a temperature-sensingdevice35 may be used to detect the temperature of the refrigerant being discharged bycompressor22. The output of temperature-sensingdevice35 may be monitored to regulate the flow of cooling liquid throughinjection line50. The cooling-liquid flow may be regulated withthrottle device48 to achieve a desired exit temperature or exit temperature range for the refrigerant discharged bycompressor22. For example, when the refrigerant is CO₂, it can be preferred to have a discharge temperature less than about 260 degrees Fahrenheit. As another example, when the refrigerant is CO₂, it can be preferable to maintain the discharge temperature between about 200 degrees Fahrenheit and up to about 250 degrees Fahrenheit.Throttle device48 may adjust the flow therethrough in response to the output of temperature-sensingdevice35 to compensate for changing operation ofcompressor22 and/orrefrigeration system20. A thermal expansion valve that is in thermal communication with the refrigerant being discharged bycompressor22 may be utilized as a temperature-compensatingthrottle device48. The thermal expansion valve may automatically adjust its position (e.g., fully opened, fully or approximately closed, or at an intermediate position therebetween) based on the temperature of the refrigerant being discharged bycompressor22 to achieve a desired exit temperature or range. Optionally, acontroller37 may monitor the temperature reported by a temperature-sensingdevice35 and adjust operation ofthrottle device48 based on the sensed temperature to maintain the desired discharge temperature or temperature range for the refrigerant being discharged bycompressor22.

Withinseparator38, the pressure typically remains above the critical pressure in trans-critical operating case, and the temperature typically remains above the saturation temperature for that pressure in the sub-critical case of operation. As a result, the refrigerant therein remains in gaseous form. The high-temperature, high-pressure gaseous refrigerant flows fromseparator38 to agas cooler51 through high-temperature, high-pressure line56. Withingas cooler51, heat Q₂is transferred from the high-temperature, high-pressure refrigerant to ambient. A fan orblower52 can facilitate the heat transfer by flowing ambient air across gas cooler51 in heat-conducting relation with the refrigerant flowing therethrough. Alternatively,gas cooler51 may be a liquid-liquid heat exchanger, such as whenrefrigeration system20 is used as a heat pump system, wherein the heat Q₂can be used to heat water flowing through the heat pump system.

The refrigerant exits gas cooler51 at a reduced temperature but still at a pressure above critical and, as a result, the refrigerant remains in gaseous form. When a suction-line heat exchanger is provided to further pre-cool the gas and superheat the suction gas returning to the compressor, the gaseous refrigerant flowing from gas cooler51 may flow to a suction-line heat exchanger54 throughline57. Withinheat exchanger54, heat Q₃is transferred from the high-pressure refrigerant to low-temperature, low-pressure refrigerant flowing to the suction side ofcompressor22. The transfer of heat Q₃reduces the temperature of the high-pressure refrigerant, which may increase the heat-absorbing capacity in the evaporator. The high-pressure refrigerant exitingheat exchanger54 may remain above the critical pressure. (When the gas is above its critical temperature it may not be anything but gaseous at any pressure, but below critical temperature it may be liquid even if above critical pressure.)

A reduced-temperature, high-pressure line58 directs the high-pressure refrigerant fromheat exchanger54 to amain throttle device60. The refrigerant flowing throughthrottle device60 expands and a further reduction in temperature and pressure occurs.Throttle device60 can be dynamically controlled to compensate for a varying load placed onrefrigeration system20. Alternatively,throttle device60 can be static.

The low-pressure refrigerant downstream ofthrottle device60 at this point of the circuit is desirably at a sub-critical temperature and at a pressure below its critical pressure, resulting in a two-phase refrigerant flow. A low-pressure line62 directs the refrigerant flowing throughthrottle device60 toevaporator64, where the two-phase, low-pressure refrigerant absorbs heat Q₄from the fluid flowing overevaporator64. For example, heat Q₄can be extracted from an air stream induced to flow overevaporator64 by a fan orblower66. The liquid portion of refrigerant withinevaporator64 boils off as heat Q₄is absorbed. Near the end of theevaporator64 as the liquid phase is boiled off, the temperature of the refrigerant increases and exits evaporator64 through a low-pressure line68, which directs the refrigerant into suction-line heat exchanger54, when it is so provided, wherein the temperature of the refrigerant further increases by the transfer of heat Q₃, prior to flowing intocompressor22 throughsuction line26.

In operation, the low-pressure (suction pressure) refrigerant exiting suction-line heat exchanger54 is sucked into the compression cavities ofcompressor22 throughsuction line26 andsuction port24. The compression members withincompressor22, such as the scrolls in the case of a scroll compressor, compress the refrigerant from the suction pressure to the discharge pressure. During the compressing process, cooling liquid is injected into the compression cavities at an intermediate-pressure location throughinjection line50.

The specific quantity of cooling liquid injected into the compression cavities can vary based on factors including, but not limited to, the demand placed onrefrigeration system20, the type of refrigerant utilized therein, the type and configuration ofcompressor22, the efficiency of the compressor, the suction and discharge pressures, the heat capacity of the cooling liquid, and the ability of the selected cooling liquid to absorb the refrigerant at different pressures and temperatures. Injecting larger amounts of cooling liquid into the working chamber of the compressor allows the working process to approach a quasi isothermal compression process. However, the cooling-liquid injection process can also be associated with additional losses caused by the energy required to pump the cooling-liquid to a higher pressure, increased throttling of the cooling liquid before injection into the compression cavities, and parasitic recompression of refrigerant through dissolution in the cooling liquid under high pressure and release at a lower pressure. It is understood to those skilled in the art that for a given operational condition, selected working fluids, and compressor parameters there is an optimal range of cooling liquid volume that may be injected in order to achieve the desired refrigeration system performance given that the discharge gas may not exceed a maximum allowable temperature.

The quantity of cooling liquid injected into the compression cavities at the intermediate-pressure location may absorb a significant amount of the heat generated by the compression process. As a result, there may be a minimal or no need to further cool the discharged refrigerant as adequate cooling may be achieved with the cooling liquid and the absorbed heat may be released inheat exchanger42, which extracts heat Q₁from the cooling liquid flowing therethrough. The ability to remove the heat generated by the compression process with the injected cooling liquid may eliminate the need for a discharge gas cooler or condenser to reduce the discharge gas temperature prior to flowing through the rest of the refrigeration system. When this is the case,gas cooler51 is not needed andline56′ (shown in phantom) directs the high-pressure refrigerant toline57. Thus, the use of injected cooling liquid, which may enable the compression process to approach quasi-isothermal compression withincompressor22, may also simplify the design ofrefrigeration system20 and enable a significant portion of the compression heat to be absorbed by the injected cooling liquid and rejected throughheat exchanger42.

Because the injected cooling liquid significantly reduces the temperatures associated with the compression process,compressor22 is relieved from excessive temperatures and the compression process temperatures are less dependent on the temperature of the refrigerant entering the suction side ofcompressor22 throughsuction port24. By reducing this dependency on compression process temperatures, a suction-line heat exchanger54 may be used to improve the refrigeration cycle efficiency. Furthermore, the presence of the injected cooling liquid during the compression process promotes sealing the gaps separating the compression cavities during the compression process, which may further reduce the compression work needed to compress the refrigerant from a suction pressure to a discharge pressure. Thus, cooling-liquid injection system33 can be a beneficial addition torefrigeration system20.

Referring now toFIG. 2, arefrigeration system120 according to the present teachings is shown.Refrigeration system120 is similar torefrigeration system20, discussed above and shown inFIG. 1, with the addition of aneconomizer system170. As such,refrigeration system120 includes acompressor122 having inlet and

outlet ports

124,128 respectively connected to suction and

discharge lines

126,130. Refrigerant and cooling liquid discharged bycompressor122 flows through a liquid/gas separator138 wherein the cooling liquid is removed throughline140 and routed throughheat exchanger142. A fan orblower144 may facilitate the removal of heat Q₁₀₁from the cooling liquid inheat exchanger142. The reduced-temperature cooling liquid exitsheat exchanger142 throughline146, flows through a throttle/expansion device148, and is injected into the pressure cavities at an intermediate-pressure location throughline150 and intermediate-pressure port132.Expansion device148 can be the same asexpansion device48 and can be operated in the same manner. As such, acontroller137 can be coupled to a temperature-sensingdevice135 to control the opening and closing ofthrottle device148.

Gaseous refrigerant flows fromseparator138 into gas cooler151 throughline156.Gas cooler151 transfers heat Q₁₀₂from the refrigerant flowing therethrough to ambient. A fan orblower152 may facilitate the removal of heat Q₁₀₂from the refrigerant flowing throughgas cooler151. Optionally, if a gas cooler is not utilized, refrigerant exitsseparator138 and flows directly toline157 throughline156′ (shown in phantom). Refrigerant exiting gas cooler151 flows into suction-line heat exchanger154 throughline157.Heat exchanger154 transfers heat Q₁₀₃from the refrigerant flowing therethrough fromline157 to refrigerant flowing through the lower pressure side ofheat exchanger154 fromline168.

Refrigeration system

120 also includes a main throttle/expansion device160 that expands the refrigerant on its way toevaporator164 throughline162. Inevaporator164, heat Q₁₀₄is transferred from a fluid flowing overevaporator164 and into the refrigerant flowing therethrough. A fan orblower166 may facilitate the fluid flow over the exterior ofevaporator164. The refrigerant exitsevaporator164 and flows to suction-line heat exchanger154 throughline168.

Refrigeration system

120 differs fromrefrigeration system20 by including aneconomizer system170, which may further reduce the operational temperature of the refrigerant prior to flowing throughmain expansion device160 thereby increasing its capacity to absorb heat inevaporator164 and increasing the cooling capacity ofrefrigeration system120.Economizer system170 injects refrigerant, in vapor form, directly into the compression cavities at an intermediate-pressure location. While similarities and differences betweenrefrigeration system20 andrefrigeration system120 will be discussed, other similarities and differences may exist.

Compressor

122 may include a second intermediate-pressure port134 for injection of refrigerant vapor into the compression cavities at an intermediate-pressure location. The use of separate intermediate-

pressure ports

132,134 allows the refrigerant-vapor injection to be kept separate from the cooling-liquid injection. The use of separate injection ports may also reduce or eliminate the need to control injection of the cooling liquid and the refrigerant vapor because the injection pressures and flow rates would not necessarily be coordinated. Additionally, the potential for backflow of one fluid into the sources of the other flow may also be reduced and/or eliminated. Thus, separate injection ports allow cooling liquid and vapor injection to occur at different locations and at different intermediate-pressure levels can be used.

Economizer system

170 may include aneconomizer heat exchanger174 disposed in-line with high-pressure line158. A portion of the refrigerant flowing throughline158 downstream of a high-pressure side ofeconomizer heat exchanger174 may be routed through aneconomizer line176, expanded in aneconomizer throttle device178 and directed into a reduced-pressure side ofeconomizer heat exchanger174. The portion of the refrigerant flowing througheconomizer throttle device178 is expanded such that it can absorb heat Q₁₀₅from the high-pressure gaseous refrigerant flowing through the high-pressure side ofheat exchanger174. The refrigerant expanded acrossthrottle device178 should be cool enough to be a two-phase mixture. The transfer of heat Q₁₀₅from the main refrigerant flow decreases the temperature prior to encounteringmain throttle device160 and flowing ontoevaporator164 vialine162, thereby increasing the heat absorbing capacity of the refrigerant and improving the performance ofevaporator164. The refrigerant exitsevaporator164 throughline168 and flows into an optional suction-line heat exchanger154 to absorb heat Q₁₀₃.

The expanded and heated refrigerant vapor exitingeconomizer heat exchanger174 flows through vapor-injection line180 to second intermediate-pressure port134 for injection into the compression cavities at an intermediate-pressure location. The refrigerant flow rate injected into the compression cavities at an intermediate-pressure location through vapor-injection line180 may be equal to or greater than the refrigerant flow rate into thesuction port124 ofcompressor122 throughsuction line126.Throttle device178 maintains the pressure in vapor-injection line180 above the pressure at the intermediate-pressure location of the compression cavities that communicate with second intermediate-pressure port134.Throttle device178 may be a dynamic device or a static device, as desired, to provide a desired economizer effect. Refrigerant-vapor injection at an intermediate pressure reduces the amount of energy used bycompressor122 to compress the injected vapor to discharge pressure, thereby reducing the specific work improving compressor efficiency.

Refrigeration system

120 includes injection of a cooling liquid into the compression cavities at an intermediate-pressure location and injection of refrigerant vapor into the compression cavities at another intermediate-pressure location. Cooling-liquid injection and vapor-refrigerant injection improverefrigeration system120 efficiency by increasing the performance ofcompressor122 andevaporator164. The injection of the cooling liquid can reduce the impact of an increased temperature of the suction gas caused by the use of suctiongas heat exchanger154. Lowering the temperature of the compressed refrigerant discharged bycompressor122 facilitates the use of aneconomizer system170 to further reduce the temperature of the refrigerant prior to flowing through themain throttle device160 andevaporator164. The reduced discharge temperature enableseconomizer system170 to further reduce the refrigerant temperature to a temperature lower than that achieved with a refrigerant discharged at a higher temperature. Thus, the combination of a vapor-injection economizer system170 and cooling-liquid injection system133 may provide a more economical andefficient refrigeration system120.

Referring now toFIG. 3, arefrigeration system220 according to the present teachings is shown.Refrigeration system220 is similar torefrigeration system120 discussed above with reference toFIG. 2. As such,refrigeration system220 includes acompressor222 having inlet and

outlet ports

224,228 respectively connected to suction and

discharge lines

226,230. Refrigerant and cooling liquid discharged bycompressor222 flows through a liquid/gas separator238 wherein the cooling liquid is removed throughline240 and routed throughheat exchanger242. A fan orblower244 may facilitate the removal of heat Q₂₀₁from the cooling liquid inheat exchanger242. The reduced-temperature cooling liquid exitsheat exchanger242 throughline246, flows through a throttle/expansion device248, and is injected into the pressure cavities at an intermediate-pressure location throughline250 and intermediate-pressure port232.Expansion device248 can be the same asexpansion device148 and can be operated in the same manner. As such, acontroller237 can be coupled to a temperature-sensingdevice235 to control the opening and closing ofthrottle device248.

Gaseous refrigerant flows fromseparator238 into gas cooler251 throughline256.Gas cooler251 transfers heat Q₂₀₂from the refrigerant flowing therethrough to ambient. A fan orblower252 may facilitate the removal of heat Q₂₀₂from the refrigerant flowing throughgas cooler251. Optionally, if a gas cooler is not utilized, refrigerant exitsseparator238 and flows directly toline257 throughline256′ (shown in phantom). Refrigerant exiting gas cooler251 flows into suction-line heat exchanger254 throughline257.Heat exchanger254 transfers heat Q₂₀₃from the refrigerant flowing therethrough fromline257 to refrigerant flowing through the lower pressure side ofheat exchanger254 fromline268.

Refrigeration system

220 also includes amain throttle device260 that expands the refrigerant on its way toevaporator264 throughline262. Inevaporator264, heat Q₂₀₄is transferred from a fluid flowing overevaporator264 and into the refrigerant flowing therethrough. A fan orblower266 may facilitate the fluid flow over the exterior ofevaporator264. The refrigerant exitsevaporator264 and flows to suction-line heat exchanger254 throughline268.

Refrigeration system

220 includes both cooling-liquid injection and refrigerant-vapor injection into the compression cavities ofcompressor222 at intermediate-pressure locations.Refrigeration system220, however, may use adifferent economizer system270 thanrefrigeration system120. While similarities and differences betweenrefrigeration system220 andrefrigeration system120 will be discussed, other similarities and differences may exist.

Inrefrigeration system220, high-pressure line258 includes athrottle device282 and aflash tank284 downstream of suction-line heat exchanger254. The high-pressure refrigerant flowing throughthrottle device282 and intoflash tank284 is expanded to reduce the pressure to a sub-critical pressure and form a two-phase refrigerant flow.Throttle device282 reduces the pressure of the refrigerant flowing therethrough to a pressure that is between the suction and discharge pressures ofcompressor222 and is greater than the intermediate pressure in the compression cavities that communicate with second intermediate-pressure port234.Throttle device282 may be dynamic or static.

Inflash tank284 the gaseous refrigerant can be separated from the liquid refrigerant and may be routed to second intermediate-pressure port234 through vapor-injection line286 for injection into the compression cavities at an intermediate-pressure location. The refrigerant flow rate injected into the compression cavities at an intermediate-pressure location through vapor-injection line286 may be equal to or greater than the refrigerant flow rate into thesuction port224 ofcompressor222 throughsuction line226. The liquid refrigerant inflash tank284 may continue throughline258 and throughmain throttle device260 and intoevaporator264 throughline262. The refrigerant withinevaporator264 absorbs heat Q₂₀₄and returns to gaseous form. The refrigerant flows, vialine268, fromevaporator264 to suction-line heat exchanger254, absorbs heat Q₂₀₃from refrigerant flowing to suction-line heat exchanger254 throughline257, and flows into the suction side ofcompressor222 throughsuction line226 andsuction port224.

Refrigeration system

220 utilizes both cooling-liquid injection system233 to inject cooling liquid intocompressor222 andeconomizer system270 to inject vapor-refrigerant intocompressor222 to increase the efficiency and/or the cooling capacity ofcompressor222 and improve the performance ofrefrigeration system220. Thus,refrigeration system220 may include cooling-liquid injection and refrigerant-vapor injection into the pressure cavities at different intermediate-pressure locations.

Referring now toFIG. 4, anotherrefrigeration system320 according to the present teachings is shown.Refrigeration system320 is similar torefrigeration system120, discussed above and shown inFIG. 2, and includes a cooling-liquid injection system333, aneconomizer system370, and adds a liquid-refrigerant injection system372. While the similarities and differences betweenrefrigeration system320 andrefrigeration system120 will be discussed, other similarities and differences may exist.

Refrigeration system

320 includes acompressor322 having inlet and discharge

ports

324,328 coupled to suction and

discharge lines

326,330, respectively.Compressor322 includes intermediate-pressure port332 that communicates with cooling-liquid injection line350 to receive the cooling liquid. Thedischarge line330 communicates with a gas/liquid separator338, which separates the cooling liquid from the refrigerant and transfers the cooling liquid toheat exchanger342 throughline340 to remove heat Q₃₀₁from the cooling liquid. A fan orblower344 may facilitate the heat removal. The reduced-temperature cooling liquid exitsheat exchanger342 throughline346, flows through a throttle/expansion device348, and is injected into the pressure cavities at an intermediate-pressure location throughline350 and intermediate-pressure port332.Expansion device348 can be the same asexpansion device148 and can be operated in the same manner. As such, acontroller337 can be coupled to a temperature-sensingdevice335 to control the opening and closing ofthrottle device348.

Gaseous refrigerant flows fromseparator338 into gas cooler351 throughline356.Gas cooler351 transfers heat Q₃₀₂from the refrigerant flowing therethrough to ambient. A fan orblower352 may facilitate the removal of heat Q₃₀₂from the refrigerant flowing throughgas cooler351. Optionally, if a gas cooler is not utilized, refrigerant exitsseparator338 and flows directly toline357 throughline356′ (shown in phantom). Refrigerant exiting gas cooler351 flows into suction-line heat exchanger354 throughline357. Withinheat exchanger354, heat Q₃₀₃is transferred from the high-pressure refrigerant to low-pressure refrigerant flowing fromevaporator364 throughline368 and through the low-pressure side of suction-line heat exchanger354. The increased-temperature refrigerant flows from suction-line heat exchanger354 into the suction side ofcompressor322 throughinlet port324 andsuction line326.

Refrigeration system

320 may includeeconomizer system370, which may include aneconomizer heat exchanger374 disposed in-line with high-pressure line358. A portion of the refrigerant flowing throughline358 downstream of a high-pressure side ofeconomizer heat exchanger374 may be routed through aneconomizer line376, expanded in aneconomizer throttle device378, and directed into a reduced-pressure side ofeconomizer heat exchanger374 wherein the expanded refrigerant absorbs heat Q₃₀₅from the high-pressure refrigerant flowing through the high-pressure side ofeconomizer heat exchanger374. The expanded and heated refrigerant vapor exitingeconomizer heat exchanger374 flows to second intermediate-pressure port334 through vapor-injection line380 and is injected into the compression cavities at an intermediate-pressure location. The refrigerant flow rate injected into the compression cavities at an intermediate-pressure location through vapor-injection line380 may be equal to or greater than the refrigerant flow rate into thesuction port324 ofcompressor322 throughsuction line326.

The main stream of the refrigerant flowing throughline358 flows through amain throttle device360 and intoevaporator364 through low-pressure line362. The refrigerant flowing throughevaporator364 absorbs heat Q₃₀₄from the fluid flowing over the exterior ofevaporator364. A fan orblower366 can facilitate the heat transfer Q₃₀₄by inducing the fluid flow overevaporator364. The refrigerant exitsevaporator364 and flows to suction-line heat exchanger354 throughline368.

Refrigeration system

320 includes a liquid-refrigerant injection system372 to inject liquid refrigerant into the compression cavities ofcompressor322 at an intermediate-pressure location. The injected liquid refrigerant may reduce the temperature of the compression process and the temperature of the refrigerant discharged bycompressor322.Compressor322 may include a third intermediate-pressure port336 for injecting the liquid refrigerant directly into the compression cavities at an intermediate-pressure location. Liquid-refrigerant injection system372 may include a liquid-refrigerant injection line388 in fluid communication with intermediate-pressure port336 and with high-pressure line358. Liquid-refrigerant injection line388 may communicate withline358 upstream or downstream ofeconomizer line376.

Athrottle device390 may be disposed inline388 to regulate the flow of liquid refrigerant therethrough. A portion of the refrigerant flowing throughline358, after having passed through the high-pressure side ofeconomizer heat exchanger374, may be routed through liquid-refrigerant injection line388, expanded inthrottle device390, and directed into the compression cavities ofcompressor322 at an intermediate-pressure location through intermediate-pressure port336. After passing throughthrottle device390, the refrigerant pressure is greater than the pressure in the compression cavity in fluid communication with intermediate-pressure port336. The expansion of the refrigerant flowing throughthrottle device390 may cause the refrigerant to take an entirely liquid form, or a two-phase form that is predominantly liquid in a relatively low enthalpy state.

Throttle device

390 may be dynamic, static, or quasi-static. For example,throttle device390 may be an adjustable valve, a fixed orifice, a variable orifice, a pressure regulator, and the like. When dynamic,throttle device390 may vary the amount of refrigerant flowing therethrough and injected intocompressor322 through intermediate-pressure port336 based on operation ofrefrigeration system320, operation ofcompressor322, to achieve a desired operation ofrefrigeration system320, and/or to achieve a desired operation ofcompressor322. By way of non-limiting example,throttle device390 may adjust the flow of refrigerant therethrough to achieve a desired discharge temperature or range of discharge temperature of the refrigerant exitingdischarge port328.

For temperature-based regulation of the refrigerant flow throughthrottle device390, temperature-sensingdevice335 may be used to detect the temperature of the refrigerant being discharged bycompressor322. The output of temperature-sensingdevice335 may be monitored to regulate the flow of refrigerant through liquid-refrigerant injection line388. The refrigerant flow may be regulated to achieve a desired exit temperature (preferably less than about 260 degrees Fahrenheit in the case of CO₂) or exit temperature range (preferably between about 200 degrees Fahrenheit to about 250 degrees Fahrenheit, in the case of CO₂) for the refrigerant discharged bycompressor322.Throttle device390 may adjust the flow therethrough in response to the output of temperature-sensingdevice335 to compensate for changing operation ofcompressor322 and/orrefrigeration system320. A thermal expansion valve that is in thermal communication with the refrigerant being discharged bycompressor322 may be utilized as a temperature compensatingthrottle device390. The thermal expansion valve may automatically adjust its position (e.g., fully opened, fully or approximately closed, or at an intermediate position therebetween) based on the temperature of the refrigerant being discharged bycompressor322 to achieve a desired exit temperature or range.Controller337 may monitor the temperature reported by temperature-sensingdevice335 and adjust operation ofthrottle device390 based on the sensed temperature to maintain the desired discharge temperature or temperature range for the refrigerant being discharged bycompressor322.

When cooling-liquid injection system333 uses an actively controlledthrottle device348,controller337 can control and coordinate the operation ofthrottle device348 andthrottle device390 to coordinate the cooling-liquid injection and liquid-refrigerant injection into the compression cavities ofcompressor322 to achieve a desired operational state. For example,controller337 can stage the injection of the cooling liquid and the liquid refrigerant such that one of the fluid injections provides the primary cooling and the other fluid injection provides supplemental cooling as needed. When this is the case,controller337 can use the cooling-liquid injection as the primary cooling means and actively controlthrottle device348 to adjust the flow of the cooling liquid injected intocompressor322 to achieve a desired refrigerant discharge temperature as reported by temperature-sensingdevice335.Controller337 would maintainthrottle device390 closed so long as the injection of the cooling liquid is able to achieve the desired refrigerant discharge temperature. In the event that the cooling-liquid injection is unable to meet the desired refrigerant discharge temperature,controller337 can commandthrottle device390 to open and allow liquid refrigerant to be injected intocompressor322 to provide additional cooling and achieve the desired refrigerant discharge temperature. In this manner,controller337 utilizes the cooling liquid injection as the primary cooling means and supplements the cooling capability through the injection of liquid refrigerant.

In another control scenario,controller337 can utilize cooling-liquid injection system333 and liquid-refrigerant injection system372 simultaneously to achieve a desired refrigerant discharge temperature. In this case,controller337 actively controls the opening and closing of

throttle devices

348,390 to vary the quantity of cooling liquid and liquid refrigerant injected into the intermediate-pressure cavities ofcompressor322.Controller337 adjusts

throttle devices

348,390 based on the refrigerant discharge temperature sensed by temperature-sensingdevice335.

In yet another control scenario,controller337 can utilize liquid-refrigerant injection system372 as the primary cooling means and supplement the cooling capability, as needed, with cooling-liquid injection system333. In this case,controller337 actively controlsthrottle device390 to inject liquid refrigerant into the compression cavities ofcompressor322 to achieve a desired refrigerant discharge temperature. If the liquid refrigerant injection is not sufficient to achieve the desired refrigerant discharge temperature,controller337 commandsthrottle device348 to open and close to provide cooling-liquid injection to supplement the cooling capability and achieve a desired refrigerant discharge temperature.

The injection of liquid refrigerant into the compression cavities at an intermediate-pressure location may reduce the efficiency ofcompressor322. The reduced efficiency, however, may be outweighed by the advantages torefrigeration system320 by a lower temperature refrigerant discharged bycompressor322. Additionally, any decrease in compressor efficiency caused by liquid-refrigerant injection may also be reduced and/or overcome by the advantages associated with the use of the cooling-liquid injection and/or vapor-refrigerant injection. Moreover, the injection of liquid refrigerant into the compression cavities ofcompressor322 may be modulated or regulated to minimize any compromise to the efficiency ofcompressor322 and/orrefrigeration system320 while providing a temperature reduction to refrigerant discharged bycompressor322. Best efficiency may be achieved by first injecting cooling-liquid and operating vapor injection to satisfy system cooling capacity requirement. If more cooling is required beyond maximum injection of cooling liquid (more extreme conditions) then liquid-refrigerant injection can be additionally applied, thus staging the cooling means.

Inrefrigeration system320, three intermediate-

pressure ports

332,334,336 may be used to inject a cooling liquid, vapor refrigerant, and liquid refrigerant, respectively, into the compression cavities ofcompressor322 at intermediate-pressure locations. These three ports may communicate with the compression cavities at different intermediate-pressure locations and allow the associated fluid flows to be supplied to different intermediate-pressure locations. The use of intermediate-

pressure injection ports

332,334,336 may isolate the fluids from one another prior to injection into the compression cavities. The use of

separate injection ports

332,334,336 reduces or eliminates coordination of injection pressures of the respective fluids. Additionally, the potential for backflow of one of these flows into the other flow may also be reduced or eliminated by the use of

separate injection ports

332,334,336.

Liquid refrigerant may be injected into the intermediate-pressure cavities at a location that is near the discharge port, where the most heat is generated by the compression process. As a result, injecting the liquid refrigerant into the pressure cavities at an intermediate-pressure location that is near the discharge port may provide the cooling where it is mostly needed. Moreover, injecting the liquid refrigerant near the discharge port can also reduce any parasitic impact on the amount of compressor work necessary to compress and discharge the injected liquid refrigerant.

The cooling liquid may be injected at a location near the discharge port due to the compression heat being greatest at or close to discharge. The cooling liquid can be injected at a location that corresponds to a higher or lower pressure than the location at which the liquid refrigerant is injected. Preferably, the cooling liquid is injected into a lower pressure location than the liquid refrigerant. Injecting the cooling liquid at a lower pressure location than that of the liquid refrigerant may enhance the lubricating and sealing properties of the cooling liquid.

The refrigerant vapor may be injected into the intermediate-pressure cavities at a location that corresponds to a lower pressure than where the liquid refrigerant is injected to enable injecting the amount of vapor needed to efficiently operate therefrigeration system320 at the desired operational condition. This would also result in a lower enthalpy for the liquid separated in the flash tank and an associated increase in evaporator heat capacity.

Inrefrigeration system320, the various fluid streams are separately injected into the compression cavities ofcompressor322 at discrete intermediate-pressure locations. One or more of these fluids may be mixed or joined prior to injection into the compression cavities. For example, as shown inFIG. 5, acompressor322′ can have inlet andoutlet ports324′,328′ that communicate with respective suction anddischarge lines326′,330′.Compressor322′ can compress a refrigerant flowing therethrough from a suction pressure to a discharge pressure.Compressor322′ can include first and second intermediate-pressure ports332′,334′ that communicate with different intermediate-pressure locations incompressor322′. Refrigerant vapor can be injected into an intermediate-pressure location ofcompressor322′ through vapor-injection line380′ that communicates with second intermediate-pressure port334′. The cooling liquid and liquid refrigerant can be injected into an intermediate-pressure location ofcompressor322′ through aninjection line382′ that communicates with first intermediate-pressure port332′.

In this case, cooling-liquid injection line350′ includes a backflow-prevention device383′ and communicates withinjection line382′. Similarly, liquid-refrigerant injection line388′ includes a backflow-prevention device384′ and also communicates withinjection line382′. With this arrangement, both the cooling liquid and the liquid refrigerant flow throughinjection line382′ to be injected into an intermediate-pressure location ofcompressor322′ through intermediate-pressure port332′.Throttle devices348′,390′ regulate the respective flows of cooling liquid and liquid refrigerant intoinjection line382′.Throttle devices348′,390′ can coordinate the respective flows therethrough to achieve a desired quantity of cooling liquid and liquid refrigerant injection intocompressor322′. Backflow-prevention devices383′,384′ prevent the backflow of one of the fluids into the other fluid line.Controller337′ can be utilized to control operation ofthrottle devices348′,390′ to coordinate the injections of the cooling liquid and liquid refrigerant.

As another example, as shown inFIG. 6, the vapor refrigerant, cooling liquid, and liquid refrigerant can all be injected into acompressor322″ through the same intermediate-pressure port332″. In this case, the vapor refrigerant, the cooling liquid, and the liquid refrigerant are all injected intocompressor322″ throughinjection line382″ that communicates with intermediate-pressure port332″. Vapor-injection line380″ communicates withinjection line382″ and includes a backflow-prevention device385″. Similarly, cooling-liquid injection line350″ communicates withinjection line382″ and includes a backflow-prevention device383″. Also similarly, liquid-refrigerant injection line388″ communicates withinjection line382″ and includes a backflow-prevention device384″.Throttle devices378″,348″,390″ regulate the respective flows of vapor refrigerant, cooling liquid, and liquid refrigerant intoinjection line382″.Throttle devices378″,348″,390″ can coordinate the respective flows therethrough to achieve a desired quantity of vapor refrigerant, cooling liquid, and liquid refrigerant injection intocompressor322″. Backflow-prevention devices385″,383″,348″ prevent the backflow of any one of the fluids into any one of the other fluid lines.Controller337″ can be utilized to control operation ofthrottle devices378″,348″,390″ to coordinate the injections of the vapor refrigerant, cooling liquid, and liquid refrigerant.

Refrigeration system

320 uses a liquid-refrigerant injection system372 to inject liquid refrigerant into an intermediate-pressure cavity ofcompressor322 to reduce the discharge temperature of the refrigerant and the temperatures associated with the compression process. In conjunction with the cooling-liquid injection system333, the compression process may approach or achieve isothermal compression. In conjunction with theeconomizer system370, the capacity of the refrigerant to absorb heat inevaporator364 can be increased and the cooling capacity ofrefrigeration system320 can be increased. Liquid-refrigerant injection system372 may be used, however, in a refrigeration system that does not include both theeconomizer system370 and the cooling-liquid injection system333.

Referring now toFIGS. 7-9, acompressor422 that can be used in

refrigeration systems

20,120,220,320 is shown.Compressor422 is a scroll compressor and includes ashell421 having upper and

lower shell components

421a,421bthat are attached together in a sealed relationship.Upper shell421ais provided with arefrigerant discharge port428 which may have the usual discharge valve therein (not shown). A stationary main bearing housing orbody423 and alower bearing assembly425 are secured to shell421. A driveshaft orcrankshaft427 having aneccentric crankpin429 at the upper end thereof is rotatably journaled inmain bearing housing423 and inlower bearing assembly425.Crankshaft427 has at the lower end a relatively large diameterconcentric bore431 which communicates with a radially outwardly inclined smaller diameter bore439 extending upwardly therefrom to the top ofcrankshaft427. Disposed withinbore431 is astirrer441. The lower portion oflower shell421bforms a sump which is filled with lubricant and bore431 acts as a pump to pump lubricating fluid upcrankshaft427 and intobore439 and ultimately to various portions of the compressor that require lubrication. Astrainer469 is attached to the lower portion ofshell421band directs the oil flow intobore431.

Crankshaft

427 is rotatably driven by anelectric motor443 disposed withinlower bearing assembly425.Electric motor443 includes astator443a,windings443bpassing therethrough, and arotor443crigidly mounted oncrankshaft427.

The upper surface ofmain bearing housing423 includes a flat thrust-bearing surface445 supporting anorbiting scroll447, which includes a spiral vane or wrap449 on an upper surface thereof. Projecting downwardly from the lower surface of orbitingscroll447 is acylindrical hub453 having a journal bearing465 and adrive bushing467 therein and within which crankpin429 is drivingly disposed.Crankpin429 has a flat on one surface that drivingly engages a flat surface (not shown) formed in a portion of the drive bushing to provide a radially compliant drive arrangement, such as shown in assignee's U.S. Pat. No. 4,877,382, entitled “Scroll-Type Machine with Axially Compliant Mounting,” the disclosure of which is herein incorporated by reference. AnOldham coupling463 can be positioned between and keyed to orbiting scroll447 and bearinghousing423 to prevent rotational movement or orbitingscroll447. TheOldham coupling463 may be of the type disclosed in the above-referenced U.S. Pat. No. 4,877,382; however, other Oldham couplings, such as the coupling disclosed in assignee's U.S. Pat. No. 6,231,324, entitled “Oldham Coupling for Scroll Machine,” the disclosure of which is hereby incorporated by reference, may also be used.

Anon-orbiting scroll455 includes a spiral vane or wrap459 positioned in meshing engagement withwrap449 of orbitingscroll447.Non-orbiting scroll455 has a centrally disposeddischarge passage461 communicating withdischarge port428.

Wraps

449 of orbitingscroll447 orbit relative towraps459 ofnon-orbiting scroll455 to compress fluid therein from a suction pressure to a discharge.Non-orbiting scroll455 includes a plurality of passageways that extend therethrough and open to intermediate-pressure cavities between

wraps

449,459. These passageways are extensions of the first and third intermediate-pressure ports432,436 and are used to supply cooling liquid and liquid refrigerant, respectively, to the intermediate-pressure cavities formed betweenwraps449 of orbitingscroll447 and wraps459 ofnon-orbiting scroll455. Specifically,non-orbiting scroll455 includes a pair of third intermediate-pressure port passageways436 that each have anoutlet436bthat communicate with the intermediate-pressure cavities between

wraps

449,459 close to dischargepassage461. Similarly,non-orbiting scroll455 includes a pair of first intermediate-pressure port passageways432athat haveoutlets432bthat communicate with intermediate-pressure cavities between

wraps

449,459 at a lower intermediate-pressure location thanoutlets436b. Orbitingscroll447 also includes a second intermediate-pressure port passageway434athat has a pair ofoutlets436bthat communicates with the compression cavities between

wraps

449,459 at an intermediate-pressure location that corresponds to a lower pressure thanoutlets432b.

Thus, incompressor422, the liquid refrigerant can be injected into the intermediate-pressure cavities at the location that corresponds to higher pressure than that of the vapor refrigerant and cooling liquid. The cooling liquid can be injected into the intermediate-pressure cavities at a location that corresponds to an intermediate pressure that is less than the pressure at the injection location of the liquid refrigerant but is greater than the pressure at the injection location for the vapor refrigerant.

It should be appreciated that whilecompressor422 is shown as having a pair of passageways and a single passageway corresponding to the fluid flows to be injected into the intermediate-pressure cavities, that each fluid flow to be injected can have more or less than two passageways. Furthermore, it should also be appreciated that whilecompressor422 is shown and configured for injecting three different fluid flows,compressor422 could have more or less injection passageways to accommodate more or less distinct injection flow paths.

Referring now toFIG. 10, a fragmented cross-section of a two-stage, two-cylinder rotary compressor522 suitable for use in

refrigeration systems

20,120,220, and320 is shown.Compressor522 includes ashell521 having upper and

lower portions

521a,521bsealing fixed together. Upper and

lower bearing assemblies

523,525 are disposed incompressor522. Acrankshaft527 is rotatably disposed in upper and

lower bearing assemblies

523,525. An electric motor543 (only partially shown) is operable to rotatecrankshaft527.Crankshaft527 extends through first and second

stage compression cylinders

573,575 each having a

circular compression cavity

573a,575atherein. First and second

stage compression rollers

577a,577bare disposed aroundcrankshaft527 within respective first and

second compression cavities

573a,575a.Crankshaft527 includes first and second radially outwardly extending

eccentrics

579a,579bthat can be about 180 degrees out of phase.

Eccentrics

579a,579bare respectively disposed in

compression rollers

577a,577b.

Eccentrics

579a,579bbias a portion of the

respective compression rollers

577a,577btoward the wall of the respective first and

second compression cavities

573a,575a. Rotation ofcrankshaft527 thereby causes

compression rollers

577a,577bto move eccentrically within first and

second compression cavities

573a,575ato compress a fluid flowing therethrough.

Incompressor522, the refrigerant vapor, cooling liquid, and/or liquid refrigerant can all be injected into intermediate-pressure flow path581 for injection into the secondstage compression cylinder575 along with the fluid discharged from firststage compression cylinder573. To facilitate this, aninjection line583 can communicate with intermediate-pressure flow path581 to allow the vapor refrigerant, cooling liquid, and/or liquid refrigerant to be injected intoflow path581 which is an intermediate-pressure location. Thus, a two-stage rotary compressor522 can be used to compress a refrigerant therein and can have vapor refrigerant, liquid refrigerant, and/or cooling liquid injected into an intermediate-pressure location ofcompressor522.

Referring now toFIG. 11, a fragmented cross-sectional view of anothercompressor622 suitable for use in

refrigeration systems

20,120,220, and320 is shown.Compressor622 is a screw compressor and includes ahousing621 within which a pair of

rotating screws

681a,681bis disposed.

Screws

681a,681binclude intermeshing

helical vanes

683a,683bthat engage with one another and compress a fluid flowing therebetween from a suction pressure to a discharge pressure.Male screw681ais attached to adriveshaft627 that extends therethrough and is supported at its front end by afront bearing assembly685a.Driveshaft627 can rotate screw681awithincompressor622. The female screw621bis coupled to a shaft having a front end rotatably supported in afront bearing assembly685band arear bearing687b. As

screws

681a,681brotate in opposite directions, the fluid is drawn into the cavities formed by

vanes

683a,683b. The volume available between

vanes

683a,683bprogressively degreases during rotation and compresses the fluid and pushes it toward the outlet. In this manner, screws681a,681bcompress a refrigerant from a suction pressure to a discharge pressure.

Compressor

622 can include multiple intermediate-pressure injection ports, such as intermediate-

pressure injection ports

632,634 that communicate with intermediate-pressure cavities within

vanes

683a,683bof

screws

681a,681b. In this manner, cooling liquid and vapor refrigerant can be injected into intermediate-pressure cavities ofcompressor622. It should be appreciated that a third intermediate-pressure port (not shown) to inject liquid refrigerant into the compression cavities at an intermediate-pressure location can also be employed. Thus, ascrew compressor622 can be utilized in

refrigeration systems

20,120,220,320 and can include multiple intermediate-pressure injection ports to allow fluids to be injected intocompressor622 at intermediate-pressure locations.

Referring now toFIG. 12, a schematic representation of anothercompressor722 that can be utilized in

refrigeration systems

20,120,220, and320 is shown.Compressor722 includes ahousing721 within whichcompression members789 are disposed. Incompressor722, gas/liquid separator738 is disposed withinhousing721. Thus,compressor722 includes an internal gas/liquid separator738.Compression members789 discharge the compressed fluid directly intoseparator738. Withinseparator738, the cooling liquid is separated from the gaseous refrigerant and removed therefrom throughline740. The gaseous refrigerant is routed fromseparator738 through high-pressure line756. Thus, acompressor722 having an internal gas/liquid separator738 can be utilized in

refrigeration systems

20,120,220, and320.

Referring now toFIG. 13, anothercompressor822 suitable for use in

refrigeration systems

20,120,220, and320 is shown.Compressor822 is similar tocompressor722 in that gas/liquid separator838 is disposed withinhousing821 along withcompression members889. Incompressor822, cooling-liquid system833 is integral withcompressor822. Specifically,heat exchanger842 is coupled tohousing821 bysupports891.Heat exchanger842 allows heat Q₈₀₁to be extracted from the cooling liquid flowing through cooling-liquid system833.

Additionally,compressor822 can also include anintegral gas cooler851.Gas cooler851 can be attached tohousing821 bysupports893.Gas cooler851 can remove heat Q₈₀₂from the gaseous refrigerant flowing fromseparator838. Thus, acompressor822 having an integral cooling-liquid system833 coupled thereto can be used in

compression systems

20,120,220, and320. Additionally, acompressor822 having anintegral gas cooler851 can also be utilized in

refrigeration systems

20,120,220, and320.

The use of an integral cooling-liquid system833 enables the compressor manufacturer to provide thecompressor822 and the cooling-liquid system833 as a single unit, thereby facilitating the supplying of the appropriate controls and protections forcompressor822 by the compressor manufacturer.

In the

refrigeration systems

20,120,220,320, injection of the cooling liquid, liquid refrigerant and/or the refrigerant vapor may be cyclic, continuous or regulated. For example, when the compressor is a single-stage compressor, the intermediate-pressure ports can be cyclically opened and closed in conjunction with the operation of the compression members therein. In a scroll compressor, the port(s) can be cyclically opened and closed due to the wrap of one of the scroll members blocking and unblocking an opening in the other scroll member as a result of the relative movement. In a screw compressor, the vanes of the screws can cyclically block and unblock the openings to the pressure cavities therein as a result of the movement of the screws. Continuous injection may be provided to single-stage compressors by maintaining an opening into the compression cavities at an intermediate-pressure location open at all times. Additionally, the flow paths leading to the intermediate-pressure locations of the compression cavities may include valves operated in a manner that regulates the injection of the fluid.

In a two-stage compressor, such as a reciprocating piston or rotary compressor, the injection can be continuous, cyclical or regulated. In the two-stage compressors, the cooling-liquid injection, liquid-refrigerant injection and/or vapor injection can be directed to an intermediate-pressure chamber within which refrigerant discharged by the first stage is located prior to flowing into the second stage of the compressor. The flow paths to the intermediate-pressure chamber may be continuously open to allow a continuous injection of the fluid streams. Valves may be disposed in the flow paths to provide a cyclic or regulated injection of the fluid streams. The injection of the different fluids may all be continuous, cyclic, regulated, or any combination thereof.

While

refrigeration systems

20,120,220,320 may efficiently operate using a refrigerant in the trans-critical regime, it may also be used in the sub-critical regime.

The refrigeration systems according to the present teachings have been described with reference to specific examples and configurations. It should be appreciated that changes in these configurations can be employed without deviating from the spirit and scope of the present teachings. Such variations are not to be regarded as a departure from the spirit and scope of the claims.

Claims

1. A refrigeration system comprising a compressor having a suction port, a discharge port, a first passageway, and a second passageway, said compressor compressing a refrigerant and a single-phase liquid flowing therethrough to a discharge pressure greater than a suction pressure, said first passageway through which said refrigerant in a predominantly liquid phase can be injected into a first intermediate-pressure location at a first pressure, said second passageway through which said single-phase liquid can be injected into a second intermediate-pressure location at a second pressure, said first pressure is greater than said second pressure and said first and second pressures are both greater than said suction pressure and are both less than said discharge pressure.

2. The refrigeration system ofclaim 1, further comprising:

a first throttle device actively controlling the flow of said refrigerant into said first intermediate-pressure location, said first throttle device reducing a pressure of said refrigerant to lower than said discharge pressure and greater than said first pressure thereby injecting said refrigerant in said predominantly liquid phase into said first intermediate-pressure location, and said refrigerant changing to a predominantly vapor phase inside said compressor; and

a second throttle device actively controlling the flow of said single-phase liquid into said second intermediate-pressure location, said second throttle device reducing a pressure of said single-phase liquid to lower than said discharge pressure and greater than said second pressure thereby injecting said single-phase liquid into said second intermediate-pressure location.

3. The refrigeration system ofclaim 2, wherein said first and second throttle devices are each responsive to a change in a discharge temperature of said compressor.

4. The refrigeration system ofclaim 3, wherein said first throttle device opens at a higher discharge temperature than said second throttle device such that said single-phase liquid begins flowing into said second intermediate-pressure location at a lower discharge temperature than when said refrigerant in said predominantly liquid phase begins flowing into said first intermediate-pressure location.

5. The refrigeration system ofclaim 2, wherein said first and second throttle devices are independently operable to stop all flow of said refrigerant and said single-phase liquid into said first and second intermediate-pressure locations respectively.

6. The refrigeration system ofclaim 1, further comprising:

a separator separating said refrigerant in a predominantly gas phase and said single-phase liquid;

a first flow path communicating with said separator and said first passageway and through which a first stream of refrigerant from said separator flows and is injected into said first intermediate-pressure location of said compressor, said first stream being said refrigerant in said predominantly liquid phase when injected into said first intermediate-pressure location;

a second flow path from said separator to said second passageway and through which a second stream of predominantly said single-phase liquid from said separator flows and is injected into said second intermediate-pressure location of said compressor;

a third flow path extending from said separator to said suction port, said third flow path being a main refrigerant flow path and receiving a third stream of refrigerant from said separator, said first flow path extending from said third flow path to said first passageway;

a main throttle device disposed in said third flow path downstream of a location where said first flow path extends from said third flow path, said main throttle device reducing a pressure of said third stream flowing therethrough;

an evaporator in said third flow path downstream of said main throttle device, said evaporator transferring heat into said third stream flowing therethrough; and

a heat exchanger disposed in first and second sections of said third flow path with said first and second sections in heat-transferring relation with one another through said heat exchanger, said first section being upstream of said main throttle device, said second section being downstream of said evaporator and upstream of said suction port, and said heat exchanger transferring heat from said third stream flowing through said first section into said third stream flowing through said second section.

7. The refrigeration system ofclaim 6, further comprising a gas cooler upstream of said main throttle device cooling refrigerant flowing through said third flow path.

8. The refrigeration system ofclaim 1, further comprising:

a heat exchanger reducing a temperature of said single-phase liquid and exhausting compression heat from the system; and

a throttle device between said heat exchanger and said second passageway reducing a pressure of said single-phase liquid to lower than said discharge pressure and greater than said second pressure thereby injecting said single-phase liquid into said second intermediate-pressure location.

9. The refrigeration system ofclaim 1, wherein said compressor includes a shell defining an exterior periphery of said compressor and said refrigerant flowing into said first intermediate-pressure location is in a predominantly liquid phase when passing through said shell.

10. The refrigeration system ofclaim 1, wherein said single-phase liquid flows into said second passageway solely due to a pressure difference between said separator and said second pressure.

11. The refrigeration system ofclaim 1, wherein said single-phase liquid is a lubricant.

12. The refrigeration system ofclaim 1, wherein said compressor further comprises at least two compression members intermeshed therein with compression cavities formed therebetween and said first and second intermediate-pressure locations are different ones of said cavities.

13. The refrigeration system ofclaim 1, further comprising:

a flow path extending from said discharge port to said suction port, said flow path being a main refrigerant flow path, said flow path including first and second sections wherein refrigerant in said first section is at a higher pressure than refrigerant in said second section; and

a heat exchanger disposed in said first and second sections of said flow path with said first and second sections in heat-transferring relation with one another through said heat exchanger, said heat exchanger transferring heat from refrigerant in said first section to refrigerant in said second section.

14. A refrigeration system comprising:

a compressor having a suction port, a discharge port, and a first passageway, said compressor compressing a refrigerant and a single-phase liquid flowing therethrough to a discharge pressure greater than a suction pressure, said first passageway through which said refrigerant in a predominantly liquid phase and said single-phase liquid can be injected into a first intermediate-pressure location at a first pressure, said first pressure is greater than said suction pressure and less than said discharge pressure.

15. The refrigeration system ofclaim 14, further comprising:

a first active throttle device controlling the flow of said refrigerant into said first passageway, said first throttle device reducing a pressure of said refrigerant to lower than said discharge pressure and greater than said first pressure thereby injecting said refrigerant in said predominantly liquid phase into said first intermediate-pressure location due to the pressure difference; and

a second active throttle device controlling the flow of said single-phase liquid into said first passageway, said second throttle device reducing a pressure of said single-phase liquid to lower than said discharge pressure and greater than said first pressure thereby injecting said single-phase liquid into said first intermediate-pressure location due to the pressure difference.

16. The refrigeration system ofclaim 15, wherein at least one of said first and second throttle devices is responsive to a discharge temperature of said compressor.

17. The refrigeration system ofclaim 16, wherein both of said first and second throttle devices regulate flow therethrough based on said discharge temperature of said compressor.

18. The refrigeration system ofclaim 17, wherein said first throttle device opens at a higher discharge temperature than said second throttle device such that said single-phase liquid begins flowing into said first intermediate-pressure location at a lower temperature than when said refrigerant in said predominantly liquid phase begins flowing into said first intermediate-pressure location.

19. The refrigeration system ofclaim 15, wherein at least one of said refrigerant in said predominantly liquid phase and said single-phase liquid is injected into said first intermediate-pressure location due solely to said associated pressure difference.

20. The refrigeration system ofclaim 19, wherein both of said refrigerant in said predominantly liquid phase and said single-phase liquid are injected into said first intermediate-pressure location due solely to said associated pressure difference.

21. The refrigeration system ofclaim 15, wherein said first throttle device reduces a pressure of said refrigerant thereby changing said refrigerant from a predominantly gaseous phase to said predominantly liquid phase across said first throttle device.

22. The refrigeration system ofclaim 15, wherein said compressor includes a shell defining an exterior periphery of said compressor and refrigerant flowing into said first passageway is in said predominantly liquid phase when passing through said shell.

23. The refrigeration system ofclaim 14, wherein said single-phase liquid is a lubricant.

24. The refrigeration system ofclaim 14, wherein said compressor further comprises at least two compression members intermeshed therein with compression cavities formed therebetween and said first intermediate-pressure location is one of said cavities.

25. The refrigeration system ofclaim 14, further comprising:

a first flow path extending from said separator to said first passageway and through which refrigerant from said separator flows and is injected into said first passageway in said predominantly liquid phase;

a second flow path communicating with said separator and said first passageway and through which said single-phase liquid from said separator flows and is injected into said first passageway;

a first check valve in said first flow path only allowing flow from said first flow path toward said first passageway; and

a second check valve in said second flow path only allowing flow from said second flow path toward said first passageway.

26. The refrigeration system ofclaim 14, further comprising;