US20080006046A1

US20080006046A1 - Self contained water-to-water heat pump

Info

Publication number: US20080006046A1
Application number: US11/775,739
Authority: US
Inventors: James William Slaughter
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-07-10
Filing date: 2007-07-10
Publication date: 2008-01-10

Abstract

A self-contained water-to-water heat transfer system is provided that mixes hot water produced by a heat exchange with cold output fluid expelled from the heat pump to make source fluid. More specifically, in order to reduce the fluid flow rate required within a heat pump and substantially prevent freezing of evaporator coils within the heat pump, source water fed into the heat pump is taken from a mixture of the output hot water that was generated in the heat pump and the cool water exiting the heat pump. The system alleviates the need to employ an ground loop outside of a structure that is required by traditional geothermal heating systems.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/806,902, filed Jul. 10, 2006, the entire disclosure of which is incorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates generally to a thermoelectric apparatus that transfers thermal energy from one location to another that can be used alternatively to either heat or cool an area.

BACKGROUND OF THE INVENTION

Heat pumps are basically air conditioning units that function in reverse and are commonplace in many residential and commercial structures. The most common air-to-air pumps employ a conduit filled with a thermally conductive coolant, such as Freon, that transfers heat taken from the air outside of the structure into the structure. The vapor compression cycle that facilitates the heat transfer comprises generally a conduit that carries high pressure, high temperature liquid coolant to an expansion valve that reduces the pressure of the coolant, thereby lowering its temperature and pressure. The now low temperature coolant is then directed to an evaporator, which is generally a system of coiled tubes that act as a heat exchanger. The fluid in the evaporator is placed in thermal communication with the air outside the structure so that the heat from the air is transferred to the coolant in the evaporator. Hot coolant vapor exits the evaporator and is compressed and directed to a condenser where it is placed in thermal communication with air inside the structure. To complete the vapor compression cycle, the hot liquid coolant that exits the condenser is pumped into the expansion valve.
The major drawback with air-to-air systems is that they are not very efficient in the winter. More specifically, when the outside temperature is at or below about 35° F., heat is less easy to extract. Thus, in most locations, a furnace, a stove or a fireplace, for example, must be employed during colder periods to heat the structure. Further, air-to-air heat exchange systems are prone to damage and degradation since they must be located outside of the structure.
Water-to-water heat transfer systems also exist that are more efficient than air-to-air systems, one common system employing a ground source heat pump that obtains the required thermal energy from beneath the surface of the earth as opposed to the air around a structure. More specifically, the temperature of the ground or groundwater a few feet beneath the earth's surface remains relatively constant throughout the year, even though the outdoor air temperature may fluctuate greatly with the change of seasons. For example, at a depth of approximately 6 feet, the temperature of the soil in most of the world's regions remains stable between about 45° and 70° F. Thus there exists a constant and ready supply of heat to be pulled from the ground and used as a source of heat for a heat pump to heat the structure, for example. These “geo-exchange” heat pumps utilize the earth's natural heat that is collected in winter through a series of pipes, generally referred to an “earth loop” or “ground loop,” installed below the surface of the ground or submerged in a pond or lake. An indoor heat exchange system then uses electrically driven compressors and heat exchangers in a vapor compression cycle to concentrate the earth's heat energy and selectively release it inside the dwelling at a higher temperature. As one skilled in the art will appreciate, the process can be reversed in the summer to cool the dwelling. Approximately 70% of the energy used in a geo-exchange heating and cooling system is renewable from the ground. Further, once installed, the earth loop in a geo-exchange system remains out of sight beneath the earth's surface while it works unobtrusively to tap the heating and cooling nature provides. The earth loops for a residential geo-exchange systems are installed either horizontally or vertically in the ground, or submerged in water in a pond or lake. In most cases, the fluid runs through a loop in a closed system, but open loop systems may be used where local codes permit. Each type of loop configuration has its own, unique advantages and disadvantages.
Horizontal ground closed loops are usually the most effective when adequate yard space is available and trenches are easy to dig. Trenchers or back hoes are employed to dig trenches about 3-6 feet below the ground wherein a series of parallel plastic pipes are placed in a closed loop. The trench is then back-filled while care is taken not to allow sharper objects to damage the pipes. A typical horizontal loop will be about 400-600 feet long per ton of heating and cooling capacity required. The buried or submerged pipe may be coiled in order to fit more of it into shorter trenches, but, while this reduces the amount of land space needed, it may require more pipe to achieve the same results as a single spread out pipe that can more efficiently extract or deposit thermal energy. Horizontal ground loops are easiest to install at a home that is under construction. However, new types of digging equipment that allow horizontal boring are making it possible to retrofit geo-exchange systems into existing homes with minimal disturbance to lawns. Horizontal boring machines can even allow loops to be installed under existing buildings or driveways, however such retrofitting, can be very expensive. Unfortunately, many homes being built today are in sub-divisions wherein space is limited and the use of a horizontal earth loop is not feasible.
To compensate for limited area, a vertical ground closed loop may be employed which is ideal for homes where yard space is insufficient or for large structures that require large heating and cooling loads. Vertical earth loops are also ideal when the earth is rocky close to the surface, or for retrofit applications where minimum disruption of landscaping is desired, wherein each hole contains a single loop of pipe with a u-bend at the bottom. After the pipe is inserted, the hole is back-filled or grouted. Each vertical pipe is then connected to a horizontal pipe, which may also be concealed underground, that carries fluid in a closed system to and from the geo-exchange system. Vertical loops are generally more expensive to install, but require less piping than horizontal loops because the earth at greater depths is alternatingly cooler in the summer and warmer in the winter. For example, a five ton system generally requires five holes each about 200 feet deep to be effective, which equates to 1000 feet of drilling that generally costs about $15 per foot for a total cost of about $15,000.00.
Thus it is a long felt need in its field of home heating and cooling to provide a system that is easy to install and that efficiently heats a structure without the cost associated with traditional geo-exchange heating systems. The following disclosure describes an improved system for utilizing a self contained water-to-water heat pump that does not require a ground loop.

SUMMARY OF THE INVENTION

It is one aspect of the present invention to provide a self-contained water-to-water heat transfer system that does not require the use of a ground loop as commonly employed in geo-exchange heating systems. That is, embodiments of the present invention utilize a novel method of mixing cooler water that exits a water-to-water heat pump with heated water also exiting the heat pump, and directing this mixture back into the heat pump so it can be more effectively used in a vapor compression cycle. One skilled in the art will appreciate that additional compression will be needed in order to sustain the temperature of the water exiting the heat pump, but the system as contemplated herein is more efficient than air-to-air heat pumps and do not have the drawbacks inherent in ground loop systems and/or air-to-air systems.
More specifically, one advantage of the system is that there is no need to drill or alter the landscape to provide a location for ground loops, thus, the system is less expensive to implement. Embodiments of the present invention are also self-contained wherein a single conduit system is employed that includes segments of varying temperatures that define the vapor compression cycle. In addition, due to the system's size and lack of external componentry, it may be located indoors, thereby avoiding outside exposure concerns such as temperature fluctuations and moisture. Further, since hot water (i.e. hotter than the fluid heated by the ground that enters the heat pump in a traditional system), is directed into the heat pump as the source of heat energy, the mass flow through the heat pump may be slowed dramatically. More specifically, prior art systems require a source mass flow of about 12-15 gallons per minute to prevent the coolant in the evaporator from freezing. In embodiments of the present invention, the temperature of the source fluid is about 95° F., thereby preventing coolant freezing. Thus the flow rate of source fluid may be slowed and a smaller more energy efficient source pump may be utilized.
It is another aspect of the present invention to provide a system that is easily incorporated onto current water-to-water heat pumps. That is, water-to-water heat pumps that use an external source to heat source water may be altered by the addition of embodiments of the present invention where the source of heat energy is replaced by the aforementioned preheating scheme.
It is still yet another aspect of the present invention to provide a system that can be used with traditional ground source heat exchange systems of the prior art. That is, embodiments of the present invention may be employed along with a traditional ground source earth loops wherein a single loop provides source heat that is directed to a plurality of self-contained heat pumps. Since the ground loop water is substantially cooler than the heated water generated by the heat pump, a mixing valve may be used to direct water from the traditional ground source heat pumps into a portion of the hot water exiting the heat pump to provide source water that prevents evaporator coils from freezing as described above.
The Summary of the Invention is neither intended nor should it be construed as being representative of the full extent and scope of the present invention. The present invention is set forth in various levels of detail in the Summary of the Invention as well as in the attached drawings and the Detailed Description of the Invention and no limitation as to the scope of the present invention is intended by either the inclusion or non-inclusion of elements, components, etc. in this Summary of the Invention. Additional aspects of the present invention will become more readily apparent from the Detail Description, particularly when taken together with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and together with the general description of the invention given above and the detailed description of the drawings given below, serve to explain the principles of these inventions.

FIG. 1 is a schematic of a ground source heat pump system of the prior art;

FIG. 2 is another schematic of a ground source heat pump system of the prior art;

FIG. 3 is a schematic of a self-contained water-to-water heat pump system of one embodiment of the present invention; and

FIG. 4 is a schematic of a heat pump employed in the embodiment of the present invention shown in FIG. 3.

To assist in the understanding of the embodiments of the present invention, the following list of components and associated numbering found in the drawings is provided herein.


	Component	#

	Ground Source Heat Pump System	2
	Ground Loop	6
	Heat	10
	Ground	14
	Cool Fluid	18
	Coolant Loop	22
	Cold Coolant Vapor	26
	Heat Exchanger	30
	Compressor	32
	Hot Coolant Vapor	34
	Condenser	36
	Fan	38
	Hot Coolant Liquid	42
	Expansion Valve	46
	Evaporator	48
	Heat Pump	50
	Storage Tank	54
	Radiant In-Floor Heating System	58
	Ground Loop Manifold	62
	Ground Loop First Inlet	64
	Ground Loop Second Inlet	68
	Load Loop First Inlet	72
	Load Loop Second Inlet	76
	Outlet Load Loop	78
	Outlet Ground Loop	80
	Check Valve	84
	Source Pump	88
	Pump	92
	Load In	96
	Load Out	100
	Source In	104
	Source Out	108
	Hot Water	112
	Cool Water	116
	Mixing Tee	120
	Warm Water	124
	Cold Liquid Coolant	128
	Superheated Coolant Vapor	132

It should be understood that the drawings are not necessarily to scale. In certain instances, details that are not necessary for an understanding of the invention or that render other details difficult to perceive may have been omitted. It should be understood, of course, that the invention is not necessarily limited to the particular embodiments illustrated herein.

DETAILED DESCRIPTION

Referring now to FIGS. 1 and 2, a ground source heat exchange system 2 of the prior art is shown. More specifically, as is well understood by one skilled in the art, the prior art heating system 2 employs a ground loop 6 that is positioned either horizontally or vertically within the earth surface. The latent heat 10 of the ground 14 is transferred to the cooler fluid 18 in the ground loop 6 via heat conduction. The now heated warm fluid 18 in the loop is then placed in thermal communication with a coolant loop 22 via a heat exchanger 30 wherein the heat from the ground loop 6 is transferred to coolant contained in the coolant loop 22. The cold coolant vapor 26 produced by the heat exchanger 30 is then compressed by a compressor 32, thereby converting electro-mechanical energy into heat energy that increases the temperature of the vapor. The now hot vapor 34 is then directed to a condenser 36 wherein the heat energy may be extracted therefrom via a fan 38, for example, to heat the inside of a structure. When the fan 38 removes heat from the coolant, coolant vapor condenses into hot liquid 42 that is directed to an expansion valve 46 that decreases the pressure and temperature of the hot liquid 42. Additionally, one skilled in the art will appreciate that hot liquid 42 exiting the heat pump 50 may be directed to a storage tank 54 for use in other hot water applications, such as showers, dishwashers, etc. and/or be used for radiant in-floor heating systems 58. As can be seen specifically in FIG. 2, due to the size and location for the placement of the ground loop 6, it may have to be placed vertically, wherein expensive drilling is required.
A ground source heat pump system 2 of the prior art that employs a plurality of coolant loops is shown in FIG. 1. More specifically, fluid is circulated via a ground loop 6 that employs a manifold 62 to split the flow into various loops that are in contact with the earth. The ground-heated water then is pumped into another manifold where it is split into a ground loop first inlet 64 and a ground loop second inlet 68, which are both fed into the heat pump 50. The heat pump 50 employs a heat exchanger (not shown) that allows the ground loop first inlet 64 and the ground loop second inlet 68 to exchange their heat with a load loop first inlet 72 and a load loop second inlet 76. The now heated water from the inlet load first and second loops 72, 76 are expelled via a outlet load loop 78. Also employed by the heat pump is an outlet ground loop 80 that directs fluid back into the ground loop 6. The outlet load loop 78 begins at the heat pump 50 and is directed to a storage tank 54, wherein a portion thereof is directed to a fan duct 38 to provide heated air to a structure, for example. Heated fluid may also be directed to radiant in-floor heating system 58. Various check valves 84 throughout the system ensure that the fluid in the system remains in the correct circulatory pattern. One skilled in the art will appreciate that when the fluid flow through the system is reversed, the heating system would necessarily become a cooling system. The fluid that exits the fan coil 38 and the radiant in-floor heating system 58 is directed to the storage tank 54, thereby allowing for the heat still present in the fluid to be used again, if necessary. The storage tank 54 also serves as a reservoir to provide fluid to be used by the inlet load first and second loops 72, 76.
Referring now to FIGS. 3 and 4, one embodiment of the present invention is shown. In the illustrated embodiment, the ground source loop has been eliminated. More specifically, embodiments of the present invention include a heat pump with a “load-in” conduit 96 and a “load-out” conduit 100 along with a “source-in” 104 conduit and a “source-out” 108 conduit. “Load-in” 96 and “load-out” 100 refers to conduits that supply heated water from the heat pump 50 to the storage tank 54, a hydronic fan coil 38, and/or in-floor heating devices 58. “Source-in” 104 and “source-out” 108 refers to conduits that supply warm water to the heat pump 50. Within the heat pump 50 exists a condenser 36, expansion valve 46, evaporator 48, and compressor 32 that are linked together with a conduit that stores a coolant, such as a refrigerant, a system that substantially similar to that of the prior art and should be well understood by one skilled in the art. The major difference between the embodiments of the present invention and that of the prior art is the source of heat energy directed to the source-in 104 side of the heat pump 50 is heat energy that originates from the hot water 112 of the load-out conduit 100 of the heat pump 50 that has been mixed with water from the source-out 108 side of the heat pump 50. The advantage of premixing the source-in 104 water is that the source side of the system can be pumped through the heat pump 50 at a much slower rate due to the fact that water of about 92° to 95° F. is being directed adjacent to the evaporator 46 of the heat pump 50. More specifically, prior art devices direct water of about 38° F. into the evaporator 46 at a flow rate of about 12-15 gallons per minute, thereby increasing the chance that the coolant in the evaporator coils 46 freeze. Since embodiments of the present invention utilize fluid at a much higher temperature, freezing of the evaporator coils 46 is not an issue such that a smaller and more efficient source pump 88 may be utilized. One skilled in the art will appreciate that the system as contemplated herein is not as efficient as the ground source heat pump system as currently employed, however, the system is still more efficient than an air-to-air heat pump system, as described above in outdoor temperatures that are below about 34°.
In operation, cool water 116 from the storage tank 54 is pumped into the load-in 96 side of the heat pump 50. As used herein, “cool” water 116 shall refer to water from temperatures of about 70° to 110° F. The cool water 116 is heated by the operation of the heat pump 50 and exits the heat pump 50 at a temperature of about 5° hotter than it entered the heat pump 50, up to about 115°, at a rate of about 12 gallons per minute (load-out 100). The hot water 112 is then split at a tee 120 wherein a mass flow of about 9 gallons per minute is directed to the storage tank 54 for future use in hot water applications, such as washing machines, dishwashers, showers, etc. The 9 gallon per minute flow may also be pumped into a hydronic fan coil 38 or in-floor radiant heating system 58 for use in temperature regulation of a dwelling. Once the heat is transferred from the water via the fan 38 and/or the in-floor heating system 58, it returns as cool water 116 into the storage tank 54. It is important to note that the lines are closed wherein no outside contaminations would enter the conduit. The loop is completed by a conduit that runs to a pump 92 that pumps some of the fluid stored in the storage tank 54 and return fluid from the fan 38 and/or in-floor heating system 58 conduits at a rate of approximately 12 gallons per minute to the heat pump 50 (load-in 96).
The source side of the system is basically the same as a ground loop side of the prior art however with an important modification. As stated above, the load-out side 100 of the system carries water in a conduit at approximately 115° at a rate of approximately 12 gallons per minute wherein 9 gallons per minute was directed towards the storage tank 54, fan 38, and in-floor heating 58, for example. The remaining 3 gallons per minute is directed to the source-in 104 side of the heat pump 50. More specifically, the hot water 112 from the load-out side 100 is mixed with cooler water 116 from the source-out side 108 of the heat pump 50 to supply water from about 92° to 95° F. to the heat pump 50 (source-in 104). The mixed warm water 124 is pumped at a rate of about 3 gallons per minute into the heat pump 50 and supplies the source-in side 104 of the heat pump 50. The source-out 108 water exits the heat pump 50 at about 65° at three gallons per minute, wherein approximately one gallon per minute is directed to the source-in 104 conduit and the remainder is directed to the storage tank 54, thereby adding to the 9 gallons per minute that exits the heating fan 38 and/or in-floor heating conduits 58 to produce the about 12 gallons per minute load-in 96 mass flow.
Referring now to FIG. 4, the internal componentry of the heat pump 50 is shown. More specifically, the warm water 124 (source-in 104) is placed in thermal communication with a coolant in an evaporator 48 of a vapor compression cycle loop. As the cold liquid coolant 128 interacts with the warm water 124 of the source-in 104 side, it evaporates to form hot coolant vapor 34 that is compressed by a compressor 32 and directed as superheated vapor 132 into a condenser 36. The condenser 36 allows for the load-in 96 fluid to thermally communicate with the super-heated vapor 132, thereby transferring heat from the super-heated vapor 132 into the load-out fluid 100. After the heat has been extracted from the super heated coolant vapor 132 it becomes hot liquid coolant 42 that is pumped 88 into the expansion valve 46 that decreases pressure and temperature and allows the coolant to cool into cold liquid coolant 128 to complete the cycle. Since some of the heat associated with the load side of the heating system is being taken to be mixed into the source-in 104 side, the compressor 32 must add more energy to the coolant. That is, in order to maintain the fluid temperature of the load-out side 100 of the heat pump 50, additional energy must be added via the compressor 32 to the coolant, to allow the load side of the system to consistently achieve a temperature of about 115° F.
Components of the embodiments of the present invention are readily obtainable and currently used, thereby making construction of embodiments of the prior art feasible. For example, in experiments, conduit made of copper and of ¾″ and ½″ diameter have been employed for the mixing loop and the source-in 104 loop. In addition, within the heat pump 50, a pump manufactured by Grunfoss that produces 0.70 horse power along with a compressor 32 produced by Copeland has been used. The remaining portions of the water-to-water self-contained heat pump are generally well known in the art.
While various embodiments of the present invention have been described in detail, it is apparent that modifications and alterations of those embodiments will occur to those skilled in the art. However, it is to be expressly understood that such modifications and alterations are within the scope and spirit of the present invention, as set forth in the following claims.

Claims

1. A self-contained water-to-water heat transfer system comprising:

a first fluid input conduit in communication with a heat pump;

a first fluid exit conduit in communication with said heat pump;

a second fluid input conduit in communication with a heat pump;

a second fluid exit conduit in communication with said heat pump and interconnected to said first fluid input conduit, and wherein thermal energy from said first fluid input conduit is transferred to said second fluid exit conduit;

a bypass conduit interconnecting said first fluid exit conduit and said first fluid input conduit thereby reducing the temperature of fluid in said second fluid exit conduit.