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 
       [0001]    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 
       [0002]    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 
       [0003]    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. 
         [0004]    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. 
         [0005]    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&#39;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&#39;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&#39;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&#39;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&#39;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. 
         [0006]    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. 
         [0007]    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. 
         [0008]    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 
       [0009]    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. 
         [0010]    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&#39;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. 
         [0011]    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. 
         [0012]    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. 
         [0013]    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 
         [0014]    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. 
           [0015]      FIG. 1  is a schematic of a ground source heat pump system of the prior art; 
           [0016]      FIG. 2  is another schematic of a ground source heat pump system of the prior art; 
           [0017]      FIG. 3  is a schematic of a self-contained water-to-water heat pump system of one embodiment of the present invention; and 
           [0018]      FIG. 4  is a schematic of a heat pump employed in the embodiment of the present invention shown in  FIG. 3 . 
       
    
    
       [0019]    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. 
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 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 
               
               
                   
                   
               
             
          
         
       
     
         [0020]    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 
       [0021]    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. 
         [0022]    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 . 
         [0023]    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°. 
         [0024]    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 ). 
         [0025]    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. 
         [0026]    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. 
         [0027]    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. 
         [0028]    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.