Patent Publication Number: US-2018031285-A1

Title: Thermoelectric heat pump system

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from U.S. Provisional Patent Application No. 62/367,458 filed on Jul. 27, 2016 entitled HIGH EFFICIENCY THERMOELECTRIC COOLING HEATING (TECH) AIR CONDITIONER, HEAT PUMP, HVAC SYSTEM WITH DUAL COUNBCAMTER FLOW LIQUID LOOPS AND SERIAL DISCRETE TECH-HEAT EXCHANGER ARRAY and from U.S. Provisional Patent Application No. ______ filed on Apr. 28, 2017 entitled HIGH DELTA TEMPERATURE AND COP SINGLE OR MULTI-STAGE LIQUID LOOP THERMOELECTRIC HEAT PUMP SYSTEM FOR COOLING AND HEATING HVAC AC, both of which are hereby incorporated by reference. 
    
    
     BACKGROUND 
     Heating, ventilation, and air conditioning (HVAC) systems using vapor compression (VC) apparatus are inefficient, heavy, bulky, costly to install and operate, and use refrigerants like Freon, which is detrimental to the ozone layer and the environment. Typical VC cooling systems take advantage of the energy absorption of a chemical refrigerant while it changes phase between a liquid and a gas. The operating temperature of the cold-side heat exchanger (evaporator coil) of the system comes as a result of a delicate balance between the boiling point of the refrigerant, and the relative flow-rates of refrigerant and air. The boiling point is set by the absolute pressure of the refrigerant, which is in turn determined by mechanical means. The result is that the system&#39;s cold-side heat-exchanger temperature is not directly controlled, but rather targeted to a general value that can only be true over a narrow range of boundary conditions. In order to regulate humidity, the coil temperature needs to be below that of the dew-point temperature of the living space. This temperature is typically below 45° F. For typical systems, the heat-pumping capacity is fixed. Each unit is sized for the maximum estimated instantaneous heat-load. Part-load response is accomplished by simply turning the unit on and off. Power cycling is made tolerable by the relatively large heat-capacity of the indoor space, which act to minimize the resulting temperature fluctuation. 
     BRIEF SUMMARY OF THE DISCLOSURE 
     A thermoelectric heat pump system in accordance with one or more embodiments is operable in a cooling and/or heating mode. The system comprises a thermoelectric apparatus and a liquid heat exchanger block apparatus thermally coupled to a first side of the thermoelectric apparatus. The liquid heat exchanger block apparatus includes at least one passage for flow of a heat transfer liquid therethrough. The system includes a radiator for rejecting heat from the heat transfer fluid when the thermoelectric pump system operates in a cooling mode and absorbing heat in the heat transfer fluid when the thermoelectric pump system operates in a heating mode. A convective fan associated with the radiator increases the heat transfer coefficient of the radiator. A conduit system couples the liquid heat exchanger block apparatus and the radiator for circulating the heat transfer fluid between the liquid heat exchanger block apparatus and the radiator. A second side of the thermoelectric apparatus opposite from the first side is thermally coupled to a heat source when the thermoelectric heat pump system operates in a cooling mode or to a cold source when the thermoelectric heat pump system operates in a heating mode. The thermoelectric apparatus can be powered to pump heat from the heat source in the cooling mode and pump heat to the cold source in the heating mode. 
     In accordance with one or more embodiments, a single or multi stage liquid loop thermoelectric heat pump system for cooling and/or heating is disclosed that can achieve higher delta temperature and COP then previous thermoelectric heat pump systems. Various embodiments disclosed herein utilize liquid to air heat exchangers, which have a higher heat transfer coefficient of 350 W/m2 K and therefore are more efficient at absorbing or rejecting heat compared to thermoelectric heat sinks, which have a heat transfer coefficient of 100-150 W/m2K. Various embodiments also utilize block or plate liquid heat exchangers with skived fins microchannel copper face plates in a plastic housing to increase the heat transfer confident and heat pump power density to decrease size, weight and costs of the heat pump system. Various embodiments also use multiple serial discrete plate heat exchangers to decrease delta temperature on the multiple discrete thermoelectric devices over the average delta temperature of a single larger thermoelectric plate heat exchanger of the same heat pumping power. Various embodiments use multiple serial discrete heat pumps within each liquid loop in a two stage configuration comprising three liquid loops. Single stage and multiple stage versions are also disclosed. Evaporative cooling may be provided on the heat rejection heat exchanger to further improve the COP of the system. The solid state thermoelectric heat pump described herein can be utilized in air conditioning, HVAC, refrigeration, domestic and commercial tank and tankless hot water heaters, industrial heating and cooling for process temperature control, among other applications. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  illustrate an exemplary thermoelectric heat pump system operable in heating and cooling modes in accordance with one or more embodiments. 
         FIGS. 2A-2D  illustrate an exemplary liquid heat exchanger block usable in a thermoelectric heat pump system in accordance with one or more embodiments. 
         FIG. 3  illustrates another exemplary liquid heat exchanger block usable in a thermoelectric heat pump system in accordance with one or more embodiments. 
         FIG. 4  illustrates an exemplary thermoelectric heat pump system in accordance with one or more embodiments. 
         FIG. 5  is a schematic illustrating DT reduction through a counter-flow arrangement in accordance with one or more embodiments. 
         FIG. 6  illustrates an exemplary thermoelectric heat pump system in accordance with one or more embodiments. 
         FIG. 7  illustrates an exemplary thermoelectric heat pump system in accordance with one or more embodiments. 
         FIG. 8  illustrates an exemplary thermoelectric heat pump system in accordance with one or more embodiments. 
         FIG. 9  illustrates an exemplary thermoelectric heat pump system in accordance with one or more embodiments. 
         FIG. 10  illustrates an exemplary thermoelectric heat pump system in accordance with one or more embodiments. 
         FIG. 11  illustrates an exemplary thermoelectric heat pump system in accordance with one or more embodiments. 
         FIG. 12  illustrates an exemplary thermoelectric heat pump system in accordance with one or more embodiments. 
         FIG. 13  illustrates an exemplary thermoelectric heat pump system in accordance with one or more embodiments. 
         FIG. 14  illustrates an exemplary thermoelectric heat pump system in accordance with one or more embodiments. 
         FIG. 15  illustrates an exemplary thermoelectric heat pump system in accordance with one or more embodiments. 
         FIG. 16  illustrates an exemplary thermoelectric heat pump system in accordance with one or more embodiments. 
         FIG. 17  illustrates an exemplary thermoelectric heat pump system in accordance with one or more embodiments. 
         FIG. 18  illustrates an exemplary thermoelectric heat pump system in accordance with one or more embodiments. 
         FIG. 19  illustrates an exemplary thermoelectric heat pump system in accordance with one or more embodiments. 
         FIG. 20  illustrates an exemplary thermoelectric heat pump system in accordance with one or more embodiments. 
         FIG. 21  illustrates an exemplary thermoelectric heat pump system in accordance with one or more embodiments. 
         FIG. 22  illustrates an exemplary thermoelectric heat pump system in accordance with one or more embodiments. 
         FIG. 23  illustrates an exemplary thermoelectric heat pump system in accordance with one or more embodiments. 
         FIGS. 24A-24C  illustrate an exemplary liquid heat exchanger block usable in a thermoelectric heat pump system in accordance with one or more embodiments. 
         FIGS. 25A-25C  illustrate an exemplary liquid heat exchanger block usable in a thermoelectric heat pump system in accordance with one or more embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Various embodiments disclosed herein relate to thermoelectric (TE) heat pump systems, which can be used in various heating and/or cooling applications. 
     In contrast to the mechanical VC cooling systems described above, TE devices move heat electronically. A TE heat pump is a solid-state active heat pump, which transfers heat from one side of the device to the other with consumption of electrical energy, depending on the direction of the current. In general, heat is transported across the device by the flow of charge carriers through a matrix of p-type and n-type semi-conductor materials. Since the heat is moved electronically, the module&#39;s instantaneous heat-pumping capacity can be adjusted by changing the supplied electrical current. This enables real-time fine-adjustment of the thermal capacity to compensate for changing conditions. Additionally, TE modules, as their name implies, are modular in nature and thermal systems can quite easily be constructed that contain a multitude of smaller independent cooling units working in series, in parallel or in multiple stages. These units can be arbitrarily activated or deactivated changing the effective thermal requirements of the system. This is analogous to, but far less complex than, a VC system composed of multiple independent (and proportionally smaller) compressor-coil sub-systems. This modular re-sizing acts to greatly expand the range of heat-load powers over which the system operates at peak efficiency. Unlike mechanical systems where the system&#39;s efficiency is generally highest at full load, TE coolers are most efficient at 20% to 40% of their maximum capacity. This fundamental difference allows TE-based HVAC systems to be sized smaller, so that they operate more efficiently at the average heat-load, but still maintain significant additional emergency capacity. 
     Among other advantages, TE heat pump systems in accordance with various embodiments achieve higher efficiencies than prior art TE heat pump systems that use thermoelectric to air heat exchangers. TE heat pump systems in accordance with various embodiments can be lighter in weight, more compact, less expensive to install and operate, and more efficient than mechanical based vapor phase systems in certain applications. Also, systems in accordance with various embodiments do not utilize Freon, which is detrimental to the environment but uses non-toxic water based refrigerants. Various embodiments disclosed herein provide significant improvements to current technology. Systems in accordance with one or more embodiments achieve higher efficiency then previous TE air conditioning configurations, which use TE-to-air heat exchangers that are low in efficiency. Systems in accordance with one or more embodiments can utilize one, two, or more separate heat pumps in a dual or three or more liquid loop counter flow system: one loop for heat load (e.g., room conditioning), one loop for heat rejection or adsorption, and optional additional loops in between the heat load and heat rejection loops for improved delta temperature and COP (coefficient of performance). A serial discrete TECH (thermoelectric cooler/heater)-heat exchanger array can be used to reduce delta temperature even further. Additional improvements include use of high efficiency BCAM (bipolar couple assembled module) TE modules with metallurgical sintered TE materials, evaporative cooling on the heat rejection heat exchanger, and advanced plastic or polymer liquid to thermoelectric heat exchangers with skived micro-channels copper face plates to increase heat exchanger efficiency and system overall COP while decreasing materials cost substantially compared to conventional liquid plate heat exchangers that are made completely out of one metal like copper or aluminum. Systems in accordance with one or more embodiments can be solar and/or battery powered as well since TEs work with DC current. 
     In conventional thermoelectric air conditioners or heat pumps, the heat transfer coefficient for heat sink air heat exchangers is ˜100-200 W/m̂2K. Also the conventional TE cooling heating systems utilize TE devices made with crystal grown Bi2Te3 which has very low ZT of 0.6-0.8 resulting in low efficiency. 
     Various embodiments disclosed herein utilize TE to liquid to air heat exchangers (radiators), which have a higher heat transfer coefficient of 350 W/m̂2K and therefore are more efficient at absorbing or rejecting heat than TE to air finned heat sink heat exchangers in accordance with the prior art. The heat transfer of a radiator can be increased even further by using a fan to increase air convective heat transfer from the fluid. Systems in accordance with one or more embodiments also utilize heat block or plate exchangers with skived fin microchannel copper face plates in a plastic housing to increase the heat transfer coefficient and system COP, while decreasing materials and total system costs. Also various embodiments utilize TE devices made with metallurgical Bi2Te3 powder fabricated under high pressures, which has a higher ZT of 1-1.4 resulting in higher efficiency. Systems in accordance with one or more embodiments can use one or two or more discrete heat pumps in a two or more liquid loop multistage system to achieve higher delta temperature with high COP. Evaporative cooling may also be used on the heat rejection heat exchanger to further improve COP of the system. 
       FIGS. 1A and 1B  illustrate an exemplary thermoelectric heat pump system operable in heating and cooling modes in accordance with one or more embodiments. The system includes a thermoelectric device  10 . A liquid heat exchanger block  12  is thermally coupled to a first side  11  of the thermoelectric device  10 . As will be described below, the liquid heat exchanger block  12  includes at least one passage for flow of a heat transfer liquid there through. The system includes a radiator  14  for rejecting heat from the heat transfer fluid when the thermoelectric pump system operates in a cooling mode and absorbing heat in the heat transfer fluid when the thermoelectric pump system operates in a heating mode. A convective fan  16  is associated with the radiator for increasing the heat transfer coefficient of the radiator. A conduit system  18  couples the liquid heat exchange block  12  and the radiator  14 , and with pump  19  circulates the heat transfer fluid between the liquid heat exchanger block  12  and the radiator  14 . 
     A second side  20  of the thermoelectric device  10  opposite from the first side  11  is thermally coupled to a heat source when the thermoelectric heat pump system operates in a cooling mode or to a cold source when the thermoelectric heat pump system operates in a heating mode. The thermoelectric device  10  can be powered to pump heat from the heat source in the cooling mode and pump heat to the cold source in the heating mode, depending on the direction of current flowing through the thermoelectric device  10 . 
     The heat source or cold source can be a variety of objects or environments to be heated or cooled including, e.g., spaces to be air conditioned and objects. In the  FIGS. 1A and 1B , the heat source or the cold source is depicted by a second liquid heat exchanger block  30  thermally coupled to the second side  20  of the thermoelectric device  10 . The second liquid heat exchanger block  30  includes at least one passage for flow of a second heat transfer liquid therethrough. A second radiator  32  rejects heat from the second heat transfer fluid when the thermoelectric pump system operates in a heating mode and absorbs heat in the second heat transfer fluid when the thermoelectric pump system operates in a cooling mode. A second conduit system  34  coupling the second liquid heat exchange block  30  and the second radiator  32  circulates the second heat transfer fluid between the second liquid heat exchanger block  30  and the second radiator  32 . The first and second conduit systems  18 ,  34  have a counterflow configuration. 
       FIGS. 2A-2C  illustrate top, side, and bottom views, respectively, of an exemplary liquid heat exchanger block usable in a thermoelectric heat pump system in accordance with one or more embodiments. Heat transfer fluid flows through a circuitous path through the block, exchanging heat with the block. The block can be made of high temperature plastic to reduce costs compared to a block made of all aluminum or copper. The bottom of the plastic block can include a copper plate thermal interface to increase thermal conductivity. The block could also be made out of aluminum, copper, or other metals or alloys. 
       FIG. 2D  illustrates a modified heat exchanger block in accordance with one or more embodiments, which includes an integrated pump for pumping heat transfer fluid through the conduit system. 
       FIG. 3  illustrates an exemplary radiator usable in a thermoelectric heat pump system in accordance with one or more embodiments. The radiator is a Dual Pass design radiator with flat copper fluid tubes. 
       FIG. 4  illustrates an exemplary thermoelectric heat pump system, in which a plurality of TE devices  10  and heat exchanger blocks  12 ,  30  are in a stacked arrangement. Each device  10  has a block  12  coupled to the cold loop on one side and a block  30  coupled to the hot loop on the opposite side. The blocks  12  are connected in series in the cold loop, and the blocks  30  are connected in series in the hot loop. The heat transfer fluids in the hot and cold loops are in a counterflow configuration. 
     Note that the radiators can be replaced by any thermal source or other types of heat exchangers. 
       FIG. 5  is a schematic showing a way to reduce DT through a counter-flow arrangement. In this configuration, the total required TE module size (TEC “B”) is divided into a larger number of proportionally smaller TE modules (TEC “A”). (Note that TEC “B” in this example is 33% the size of TEC “A” so that the total size is equal for each case.) The coolant is then passed from one TEC A module&#39;s heat exchanger to another in a serial fashion. The heat transfer fluids flow in opposite directions to each other on opposite sides of the TE device. The coolant changes temperature as it passes through each heat exchanger, becoming progressively warmer or cooler respectively. The counterflow arrangement allows the profiles to “nest” into each other and results in the reduction of each “segment&#39;s required DT over the monolithic (TEC “A”) case. Note that the number of segments shown in is small to simplify the example. There is no limit on the number of segments outside of practical concerns. As the segment number increases, the DT decreases and approaches the value TH 4 −TC 1 . For the HVAC case, the counter-flow configuration reduces the DT by &gt;20° F. (&gt;11° C.). 
       FIG. 6  illustrates an exemplary thermoelectric heat pump system in accordance with one or more embodiments, in which a plurality of TE devices and heat exchanger blocks are in a serial arrangement. The heat transfer fluids in each loop are in a counterflow configuration. Note that the radiators can be replaced by any thermal source. 
       FIG. 7  illustrates an exemplary thermoelectric heat pump system in accordance with one or more embodiments having a serial counter flow discrete TE heat exchanger array arrangement. Note that the radiators can be replaced by any thermal load or source. 
       FIG. 8  illustrates an exemplary thermoelectric heat pump system in accordance with one or more embodiments having a serial discrete TE heat-exchanger array condensed arrangement. Heat insulation is provided between pairs of heat exchanger blocks due to the direction of heat flow. Note that the radiators can be replaced by any thermal load or source. 
       FIG. 9  illustrates an exemplary thermoelectric heat pump system in accordance with one or more embodiments having a plurality of thermoelectric modules (TECH- 1  and TECH- 2 ) in a cascaded arrangement. 
       FIG. 10  illustrates an exemplary thermoelectric heat pump system in accordance with one or more embodiments having a plurality of thermoelectric modules (TECH- 1  and TECH- 2 ) that are spaced apart from one another, each of said thermoelectric modules having one surface in thermal contact with the liquid heat exchanger block apparatus and an opposite second side in thermal contact with the heat source or a heat exchanger to radiator. 
       FIG. 11  illustrates an exemplary thermoelectric heat pump system in accordance with one or more embodiments having a plurality of discrete thermoelectric modules spaced apart from one another. Each module is coupled to a separate liquid heat exchanger block. The blocks are arranged in series for flow of heat transfer fluid sequentially therethrough. 
       FIG. 12  illustrates an exemplary two stage thermoelectric heat pump system in accordance with one or more embodiments. In this embodiment, the heat load loop interfaces with liquid loop # 1  through a first TE-heat exchanger module. Liquid loop # 1  interfaces with liquid loop # 2  through a second TE-heat exchanger module. Heat is pumped from loop # 1  to loop # 2 , raising the temperature in liquid loop # 2  and lowering the temperature in liquid loop # 1 . 
       FIGS. 13-17  illustrate alternative exemplary two stage thermoelectric heat pump system in accordance with one or more embodiments, showing alternative TE module configurations. 
       FIGS. 18-23  illustrate various alternative two and three stage thermoelectric heat pump systems in accordance with one or more embodiments, showing alternative TE module configurations. 
       FIGS. 24A-24C  illustrate top, side, and bottom views, respectively, of an exemplary liquid heat exchanger block usable in a thermoelectric heat pump system in accordance with one or more embodiments. Heat transfer fluid flows between a series of skived microchannel fins through the block, increasing the thermal interface area. The block can be made out of copper or aluminum or be made out of high temperature plastic to lower the cost and weight of the system. The bottom of the plastic block includes a copper plate with skived microchannel fins for improved heat transfer coefficient to increase heat transfer between the liquid and the thermoelectric heat pump module. 
       FIGS. 25A-25C  illustrates a modified heat exchanger block similar to the block of  FIGS. 24A-24C , but with an integrated pump for pumping heat transfer fluid through the conduit system. 
     A TE/liquid block heat exchanger is much more thermally efficient then a TE/air heat exchanger. In addition, a TE/liquid block heat exchanger can transfer much higher heat densities then a TE/air heat exchanger. This reduces the required area of thermoelectric devices decreasing weight, size and thermoelectric and heat exchanger costs. 
     For small applications only 1 TE device with a hot and cold liquid heat exchanger can be used. However, for larger heat loads, multiple isolated or discrete TE/heat exchanger units can be used to effectively pump larger heat loads with a sufficient delta temperature between the two loops in a single or two stage system. Larger liquid to air heat exchangers can be used for larger heat loads. In applications where a higher delta temperature is required, multi-stage heat pumps can be utilized to achieve higher delta temperatures at lower COP compared to single stage systems with single layer or multi layered stacked thermoelectric devices in a cascade configuration. 
     Advances in higher COP TE devices will result in a higher COP heat pump system. Water condensation from the cold liquid to air heat exchanger can be pumped to the heat rejection liquid to air heat exchanger and evaporated on the fins of the heat exchanger to add additional cooling and increase the system COP even further. 
     This same configuration can be used for cooling a refrigerator and will be more efficient and cool faster than a conventional TE/air heat exchanger. 
     Thermoelectric heat pump systems in accordance with various embodiments can be used in various heating and/or cooling applications. For example, the systems can be set up to be used in a window or could be used remotely in the room using longer tubes/hoses to the radiator out the window. Also the systems can be scaled to larger size to be used to cool and heat the large spaces such as a whole house using a similar indoor liquid to air heat exchanger and liquid to air outdoor heat exchanger that is used in conventional vapor compression however the tubes would be filled with water/antifreeze mixture instead of Freon. Additionally, the systems in the same configuration can be used for cooling a refrigerator/freezer and will be more efficient and cool faster than a conventional TE/air heat exchanger. 
     Other exemplary applications of the thermoelectric heat pump include water heating for domestic tank and tankless water heaters and for industrial heating and cooling for processing and other applications. 
     Having thus described several illustrative embodiments, it is to be appreciated that various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to form a part of this disclosure, and are intended to be within the spirit and scope of this disclosure. While some examples presented herein involve specific combinations of functions or structural elements, it should be understood that those functions and elements may be combined in other ways according to the present disclosure to accomplish the same or different objectives. In particular, acts, elements, and features discussed in connection with one embodiment are not intended to be excluded from similar or other roles in other embodiments. Additionally, elements and components described herein may be further divided into additional components or joined together to form fewer components for performing the same functions. Accordingly, the foregoing description and attached drawings are by way of example only, and are not intended to be limiting.