US20090038779A1

Movatterモバイル変換

Info

Publication number: US20090038779A1
Application number: US12/187,141
Authority: US
Inventors: Geoffrey B. Courtright
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-08-07
Filing date: 2008-08-06
Publication date: 2009-02-12

Abstract

A fluid energy transfer system comprising at least one coil containing a fluid pumped in a first flow direction. The fluid comes from a source and returns to the same source. The coil is enclosed within a tank. The tank contains a tank fluid. The tank fluid is pumped into the tank in a closed system from at least one heat pump. The tank fluid is circulated from the heat pump into the tank through at least one jet located along a wall of the tank. The tank fluid moves in a direction starting from a first end of the tank and exiting at a second end of the tank in an flow direction opposite that of the coil fluid. The circulation of the tank fluid creates a vortex that creates an increase in the heat transfer coefficient by forced convection in immersion of the tank fluid over the coil.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority provisional application Ser. No. 60954352 filed Aug. 7, 2008.

FIELD OF THE INVENTION

The present invention relates generally to thermal energy transfer and specifically to dual fluid heating/cooling systems.

BACKGROUND OF THE INVENTION

Geothermal systems use the energy below the Earth's surface to transfer thermal energy. Below the approximately 48 inch frost line in the north, a temperature of approximately 48° F. is maintained year round in rock, aquifers and dirt. As the average above ground temperatures rise, so does the year round 48 inch below subsurface temperature to approximately 76° F. in southern Florida. A geothermal system transfers energy to or from a fluid in the geothermal system based on a difference in temperature of the surrounding earth.

Geothermal systems are typically comprised of a closed tube, a pump, and a heat pump. The pump moves a fluid through the tube, where the fluid is heated or cooled by the earth. The heat pump transfers the difference in the energy for heating/cooling.

A closed tube allows no direct interaction between the fluid and the earth. Closed tubes include vertical wells that go down into the earth, horizontal loops along the surface below the frost line and loops in the bottom on ponds. A vertical well may extend into a water table while a horizontal loop is typically above the water table.

Heat pumps include water-to-air, water-to-water, and hybrids. While geothermal systems transfer heat to and from the ground efficiently with minimal use of electricity and do not use fossil fuels, they are expensive and slow to install. A geothermal system is needed that is lower in cost and more efficient to install.

The following are thermal conductivity values for certain materials:


	Thermal conductivity	Thermal conductivity
Material	(cal/sec)/(cm²C./cm)	(W/m K)*

Diamond	—	1000
Silver	1.01	406.0
Copper	0.99	385.0
Gold	—	314
Brass	—	109.0
Aluminum	0.50	205.0
Iron	0.163	79.5
Steel	—	50.2
Lead	0.083	34.7
Mercury	—	8.3
Polypropylene	0.005	2.0
Glass, ordinary	0.0025	0.8
Concrete/Grout	0.002	0.8
Water at 20° C.	0.0014	0.6
Asbestos	0.0004	0.08
Snow (dry)	0.00026	—
Fiberglass	0.00015	0.04
Brick, insulating	—	0.15
Brick, red	—	0.6

*values from Young, Hugh D., University Physics, 7th Ed. Table 15-5; For the full table see website: http://hyperphysics.phy-str.gsu.edu/hbase/tables/thrcn.html

Conduction is defined as heat transfer by means of molecular agitation within a material without any motion of the material as a whole. The energy in a first end of a metal rod at a higher temperature will be transferred toward a second end of the rod if the second end is colder because warmer, higher speed particles in the warm end collide with slower particles, transferring energy across the rod.

Heat transfer by conduction can be used to model heat loss through a wall. For a barrier of constant thickness, the rate of heat loss is given by:

\frac{Q}{t} = \frac{κ A (T_{hot} - T_{cold})}{d}

Heat conduction Q/Time=(Thermal conductivity)×(Area)×(T_hot−T_cold)/Thickness

By entering data in the fields below, the quantity of heat loss is calculated.

SUMMARY OF THE INVENTION

The present invention provides an alternative to traditional thermal transfer systems. The present invention provides an energy transfer system comprising a fluid in an tank in contact with a second fluid contained in a separate container inside the tank. The fluids are isolated from each other. In an embodiment, a first fluid enters the tank and is circulated between a tank and a heat pump. The system comprises means to monitor and add tank fluid to the system. The tank fluid is circulated via a pump. The tank is in contact with tubing from at least one heat pump. In an embodiment, the tubing circulates a fluid from the heat pump(s) through the tank starting from a top of the tank. The fluid from the heat pump(s) enters the tank through inlets or jets that move the flow in a predetermined direction. In an embodiment, the direction is counterclockwise. The tank fluid flows from inlets at a side or top end to exit at a bottom end. In an embodiment, the inlets comprise jets attached to the tubes. In an embodiment, the tank fluid circulates through the tank to an exit at the center of the bottom of the tank. The tank fluid is pumped back to the heat pump(s) from the tank. The circulation of the fluid in the tank creates a vortex (by the flow and natural forces). The circulation is in a direction opposite the flow in a coil located within the tank and the continuous vortex flow of the fluid increases the heat transfer coefficient between the tank fluid and the coil. In an embodiment, the fluid is circulated by means of the pump and or gravity and or heat or the absence of heat. In an alternative embodiment, the fluid enters at a bottom of the tank and circulates upward.

Inside the coil is a cooled/heated fluid collected from either the ground water around the tank, wells a coil fluid source or other acceptable fluid sources. In an embodiment, the coil fluid is collected via perforated tubes within an aquifer. The coil fluid may be transferred to a second location, such as a second aquifer, for further cooling. In an embodiment, multiple collection tubes are placed in multiple locations and connected in a collection tube. A pump circulates the collected fluid in the coil in the tank. The coil fluid moves through the coil in a direction opposite of the movement of the tank fluid. In an embodiment the coil is stacked with spacers in spirals to create the maximum surface area contact with the tank fluid in the shortest time to increase the heat transfer coefficient. In an embodiment, the spirals are in a clockwise direction.

To increase the amount of heating/cooling provided by the system, more coils and or additional coils and or faster pumps are added. The tank may be connected to additional tanks serving similar functions to increase the amount of heating/cooling.

The vortex flow of fluid in the tank creates a forced convection with immersion for a much higher heat transfer coefficient. In an embodiment, the walls of the tank are fabricated from steel. In an embodiment, the outside of the tank is in contact with a silt barrier to allow the free flow of water against the outside of the tank. In an embodiment, the silt barrier or gravel or rock. Use of steel walls in direct contact with a ground water aquifer and constantly moving tank liquid on the inside of the tank(s) also increases the heat transfer coefficient. In an embodiment, the tank is a cylinder shape. In an embodiment, the tank is wider than it is tall, in an embodiment, the tank is taller than it is wide. In an embodiment, the inner tank wall comprises structures that assist in circulating the fluid, such as a manifold, a fin, a rudder, and the like.

Although the present invention can be used for any heat exchange between two isolated circulating fluids, the present invention provides a safe and practical geothermal (ground source) heating/cooling system for use anywhere in the world without fear of contamination to the environment or damage to the heat pump because it isolates the fluids from each other. In an embodiment, the system comprises at least one sensor to indicate whether the ground source water has leaked into the tank or if the heat pump refrigerant has leaked into the coil fluid to alert personnel to take steps prior to contamination. Upon an alert, the system is shut down and safely purged and repaired before continuing safe and contamination free operations.

“Fluid(s)” as used herein is intended to encompass liquid media, including but not limited to compounds and mixtures, and including additives, such as water with or without an additive, ethylene glycol, glycol ammonia, alcohols, and the like.

“Tank” as used herein means any container, receptacle, vessel or other device for holding a fluid.

The terms “tube” and “tubing” as used herein refer to a component that serves as an impervious conduit for the transmission of a fluid, including but not limited to components formed from polymers.

As used herein, the term “coil” means any structure formed by a plurality of turns of a tube or tubes.

The terms above are not to be construed in a limiting sense and have no functional significance. When a particular structure or component is referred to by the terms above, the primary purpose is simply for clarity and convenience in order to distinguish the particular structure from another.

As used herein, “approximately” means within plus or minus 25% of the term it qualifies. The term “about” means between ½ and 2 times the term it qualifies.

The devices and methods of the present invention can comprise, consist of, or consist essentially of the essential elements and limitations of the invention described herein, as well as any additional or optional ingredients, components, or limitations described herein or otherwise useful in compositions and methods of the general type as described herein.

Numerical ranges as used herein are intended to include every number and subset of numbers contained within that range, whether specifically disclosed or not. Further, these numerical ranges should be construed as providing support for a claim directed to any number or subset of numbers in that range.

All references to singular characteristics or limitations of the present invention shall include the corresponding plural characteristic or limitation, and vice versa, unless otherwise specified or clearly implied to the contrary by the context in which the reference is made.

All combinations of method or process steps as used herein can be performed in any order, unless otherwise specified or clearly implied to the contrary by the context in which the referenced combination is made.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of a sample configuration of the present invention.

FIG. 2 is a side view of a sample configuration of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention comprises a tank in contact with fluid from at least one heat pump that is pumped into the tank in a vortex flow, and a coil that contain the pumped flow of a heated/cooled fluid. The coil fluid may be a geothermally heated/cooled. The tanks may be connected to additional tanks or more coils and faster pumps serving similar functions to increase the amount of heating/cooling. In an embodiment, the tanks are buried below the ground. In an embodiment, the tanks are located in contact with a ground water aquifer.

The tank comprises a closed and slightly pressurized system with an opening so that tank fluid may be added to the system. The heated/cooled fluid also flows in a closed system from a source, such as storage container, an aquifer, etc., back to the same source. In an embodiment where the source is an aquifer, the flow is without contamination. The invention comprises at least one sensor that detect the amount of fluid pressure and quality of the fluid within the system. In an embodiment, the tank is cylinder-shaped. In an embodiment, the exterior wall of the thermal transfer tank is made of a durable and long-lived material, such as steel or other inert material. In an embodiment, the tanks are each approximately 12 ft×4 ft, having a wall approximately 0.25 inches thick, although any environmentally friendly material size and thickness is adaptable to the present invention. In an embodiment the tank is a 55 gallon drum.

The pumps (and natural forces) move a tank liquid inside the tanks in a vortex flow. The vortex flow is created by the location of the fluid inlets and outlets, gravity and earth rotation as the tank fluid is moved by pumping action at the rate of flow required to produce the desired heating/cooling. In the Northern Hemisphere, the tank fluid typically circulates in a counterclockwise direction; in the Southern Hemisphere, the tank fluid typically circulates in a clockwise direction. The vortex flow can be liken to a wind chill factor—it greatly increases the thermal transfer between the heat pump fluid in the tank and the fluid in the geothermally heated/cooled fluid in the coils of tubing in the tank. In an embodiment, the surrounding earth is an aquifer which also increases the heat transfer coefficient by transfer of heat through the tank wall. The tank liquid is moved by a pump to create a vortex flow so that the tank liquid continuously flows over the coil(s) and the wall. In an embodiment, the pumps are low-power so that alternative energy sources may be employed to energize the pumps.

In an embodiment, tubing from a pump is connected to the tank. A heat pump fluid flows from the heat pump through the tank and back to the heat pump. In an embodiment using multiple tanks, each tank is connected to the other such that the point near the top end of the each tank is connected to the bottom of the next tank. The tank fluid is circulated to transfer energy to or absorb energy from the heated/cooled fluid. In an embodiment where the system is located in a ground water aquifer, the flow of the aquifer is at an about 90 degree angle to a line formed by the tanks. The tank fluid flowing past the tank wall absorbs/transfers energy through the wall to/from the aquifer and will thereby not interfere with the other tanks.

The fluid in the tank is pumped from an outlet located at the bottom of one tank to an inlet set of jets in the next tank. In an embodiment, any thermal transfer tank is located a minimum of 10 feet from another thermal transfer tank. The tank fluid is circulated from the bottom to the top of the next thermal transfer tank in a first directional vortex. The tank fluid transfers energy to/from the fluid flowing in the coil spiraling in the opposite direction. In this manner, the tank fluid contacts the coil fluid with the greatest velocity to increase the forced convection.

Where more than one thermal transfer tank is used, the tanks are interconnected to each other to increase efficiency. Each tank is located a minimum of 10 feet from the next tank to minimize heat transfer interference.

In an embodiment, where the tank is a 55 gallon drum and the coil is an about 1000 foot long, about ⅜″ diameter polyethylene tube, the invention yield about 20 to about 40 T of cooling.

To demonstrate the efficiency of the present invention, the following comparison of a grout filled well vs. an embodiment of the invention is presented. Thermal conductivity values from the Heat Conduction and Thermal Conductivity information (provided above) of 0.8 W/m K for a grout filled well and 50.2 W/m K for a steel tank were used in a generally accepted formula for a heat pump to produce one ton of cooling—a 3 gallon per minute (gpm) cooling rate of 10° F., i.e. 95° F. coming out cooled down to 85° F. using a 75° F. cooling source.

The heat transfer for one 150 ft grout filled well for 1 ton of cooling for 95° F. to 85° F. at 3 gpm is as follows:

The heat transfer for forty 150 ft wells equals 8433×40=337,320 BTU/hr or about 40 tons of cooling.

In performing the heat transfer calculation for one 12 ft×4 ft steel tank for cooling 95° F. to 85° F.:

then the conduction heat loss rate is

Q / t = 6614446 BTU / hr .

(note: The actual BTU and tonnage is based on a temperature range, which can vary)

In the example, the heat transfer for one 12 ft×4 ft steel tank equals 6,614,446 BTU/hr or about 800 tons of cooling. Therefore, the single steel tank has 20 times the heat transfer capacity of the forty 150 ft wells. The present invention accomplishes a tremendous cost savings over drilling forty wells or laying 40,000 feet of tubing horizontally.

Another benefit of the present invention is that, when a relatively low cost material such as polyethylene is used to form the coil, many more of feet can be added to the thermal transfer tanks than can be put down the forty wells. In addition, the forced convection heat transfer coefficient over the coils is increased by 10 to 50 times with the circulation of the fluid in a vortex and the tank internally moves more than 10 times the volume of fluid over the heat transfer surface of the coils and tank wall in any given period compared to the forty wells. Therefore, the heat transfer is a minimum of an additional 100 times more effective than the transfer in the comparable example of the forty wells.

The heat transfer is only limited by the flow of the coil fluid. The faster the flow of the fluid, the faster will be the heat transfer. By adding jets, manifolds, using smaller diameter coils and or more coils in the tank, fluid moves faster. In addition, after moving through the coils in the tank, the coil fluid can be directed to another location or poured over the tanks to drain back into the aquifer below the tank if it is above the ground water aquifer level. With the tanks below the ground water level, the heat transfer is maximized and is at a minimum of at least about ten times more effective than in conventional wells, even when factoring in the electricity used to pump the water between the tanks.

The tanks function in the same manner of flow for both heating and cooling thermal transfers and are much more efficient when heating and cooling are taking place simultaneously—as with using hot gas reheat to effect control over both temperature and humidity. Therefore, in the present invention, some heat pump units could be cooling while others are simultaneously heating or performing reheating.

Overall Heat Transfer Coefficient

Calculating the overall heat transfer coefficient in walls or heat exchangers

The overall heat transfer coefficient for a wall can be calculated as:

1/UA=1/h₁A₁+dx_w/kA+1/h₂A₂ (1)

where

- U=the overall heat transfer coefficient (W/m²K)
- A=the contact area for each fluid side (m²)
- k=the thermal conductivity of the material (W/mK)
- h=the individual convection heat transfer coefficient for each fluid (W/m²K)
- dx_w=the wall thickness (m)

The thermal conductivity—k—for some typical materials:

- Polypropylene PP—0.12 W/mK
- Stainless steel—21 W/mK
- Aluminum—221 W/mK

The convection heat transfer coefficient—h—depends on

- the type of fluid—gas or liquid
- the flow properties such as velocity
- other flow and temperature dependent properties

Heat transfer coefficient for some common fluids:

- Air—10 to 100 W/m²K
- Water—500 to 10000 W/m²K

EXAMPLEHeat Transfer in a Heat Exchange

A single plate exchanger with media A transfers heat to media B. The wall thickness is 0.1 mm and the material is polypropylene PP, aluminum or stainless steel. Media A and B are air with a convection heat transfer coefficient of h_air=50 W/m²K. The overall heat transfer coefficient U per unit area can be expressed as:

U=1/(1/h_A+dx_w/k+1/h_B) (1b)

Using the values from above the overall heat transfer coefficient can be calculated to:

- Polypropylene PP: U=24.5 W/m²K
- Steel: U=25.0 W/m²K
- Aluminum: U=25.0 W/m²K

Cooling Mode and Heat Flux

Heat flux for various cooling modes

The table below can be used to indicate the maximum heat flux for various cooling modes.


		Heat Flux
	Cooling Mode	(kW/m²)

	Free Convection Air	0.5
	Forced Convection Air	5
	Free Convection Immersion	10
	Forced Convection Immersion	500
	Forced Convection Boiling	1000
	Impingement Air	10
	Jet Immersion, single phase	400
	Jet Immersion, boiling	900

- 1 Btu/ft²h=3.1525 W/m²

Overall Heat Transfer Coefficients for Some Common Fluids and Heat Exchanger Surfaces

Average overall heat transmission coefficients for some common fluids and surface combinations as Water to Air, Water to Water, Air to Air, Steam to Water and can be used to calculate the total heat transfer through a wall or heat exchanger construction. The overall heat transfer coefficient depends on the fluids and their properties on both sides of the wall, and the properties of the wall and the transmission surface. For still fluids—average values for the overall heat transmission coefficient through different combinations of fluids on both sides of the wall and type of wall—can be found in the table below:


	Overall Heat Transmission
	Coefficient

Fluid	Transmission Surface	Fluid	(Btu/ft²hr ° F.)	(W/m²K)

Water	Cast Iron	Air or Gas	1.4	7.9
Water	Mild Steel	Air or Gas	2.0	11.3
Water	Copper	Air or Gas	2.3	13.1
Water	Cast Iron	Water	40-50	230-280
Water	Mild Steel	Water	60-70	340-400
Water	Copper	Water	60-80	340-455
Air	Cast Iron	Air	1.0	5.7
Air	Mild Steel	Air	1.4	7.9
Steam	Cast Iron	Air	2.0	11.3
Steam	Mild Steel	Air	2.5	14.2
Steam	Copper	Air	3.0	17
Steam	Cast Iron	Water	160	910
Steam	Mild Steel	Water	185	1050
Steam	Copper	Water	205	1160
Steam	Stainless Steel	Water	120	680

1 Btu/ft²hr ° F. = 5.678 W/m²K = 4.882 kcal/h m²° C. - Unit Converter

These coefficients are rough and depend on the fluid velocities, their viscosity, the condition of the heating surfaces, the size of the temperature differences, etc., (from www.EngineeringToolBox.com).

The foregoing descriptions of specific embodiments and examples of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. It will be understood that the invention is intended to cover alternatives, modifications and equivalents. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. The Figures and the examples are merely to provided for illustration. One skilled in the art would understand that many variations of the materials of the tank, coils, parts, directions of flow in coils and tank, fluid composition, pumps sizing for both the heat pump fluid and the geothermally heated/cooled fluid, manifold design for each flow, number of and kinds of various sensors, and the like, are to maximize the efficiency and volume of the flow rate in and out of the tank and coils. It is therefore to be understood that within the scope of the claims, the invention may be practiced otherwise than as specifically described herein.

Claims

1. A fluid energy transfer system comprising at least one coil containing a fluid pumped in a first flow direction, said coil fluid coming from a source and returning to the same source, said coil enclosed within a tank, said tank containing a tank fluid, said tank fluid pumped into the tank in a closed system from at least one heat pump, said tank fluid circulating from the heat pump into the tank through at least one jet located along a wall of the tank, said tank fluid moving in a direction starting from a first end of the tank and exiting at a second end of the tank in a flow direction opposite that of the coil fluid, said circulation of the tank fluid creating a vortex that creates an increase in the heat transfer coefficient by forced convection in immersion of the tank fluid over the coil.

2. The system ofclaim 1 wherein the fluid is pumped from an aquifer and returned to the same aquifer.

3. The system ofclaim 1 wherein the tank is located in an aquifer below the level of ground water.

4. The system ofclaim 1 wherein more than one tank is interconnected and the tank fluid is circulated between the tanks from the side of a first tank and exiting at a center of a bottom end of the first tank, to a side of each additional tank and exiting at a center of a bottom end of each tank.

5. The system ofclaim 4 wherein each tank is distanced at least 10 feet from another tank.

6. The system ofclaim 1 wherein the coil fluid is water and the tank fluid is a refrigerant.

7. The system ofclaim 1 wherein the coil fluid and the tank fluid are in separately contained structures and wherein a least one sensor alerts when either fluid leaks from its structure.

8. A method of transferring energy comprising creating a vortex in a fluid in a tank, said fluid pumped in a closed system from a heat pump, said vortex in a flow direction opposite that of a fluid contained within at least one coil, said coil fluid acquired from a source and returning to the same source, said coil enclosed within the tank, said vortex creating an increase in the heat transfer coefficient by forced convection in immersion of the tank fluid over the coil.

9. A method of transferring energy comprising creating a vortex in a fluid in a tank, said tank located in an aquifer below the ground water level, said fluid pumped in a closed system from a heat pump, said vortex in a flow direction opposite that of a fluid contained within at least one coil, said coil fluid geothermally acquired from a source and returning to the same source, said coil enclosed within the tank, said vortex creating an increase in the heat transfer coefficient by forced convection in immersion of the tank fluid over the coil.

10. The method ofclaim 8 wherein multiple tanks are interconnected.