Thermoelectric heat pump

Abstract

The present disclosure relates to a thermoelectric heat pump comprising a heat exchanger block having a first channel for flowing a first heat transfer fluid such as a liquid medium, and a second channel separate from the first channel for flowing a second heat transfer fluid such as a liquid medium, the heat exchanger block comprising a heat exchange cavity including a first sub-cavity and a second sub-cavity fluidically separated by a partition, the first sub-cavity and the second sub-cavity being fluidically connected to the first channel and the second channel, respectively, the first heat transfer fluid in the first sub-cavity being in heat exchange contact with a first side surface of the partition, the second heat transfer fluid in the second sub-cavity being in heat exchange contact with a second side surface opposite to the first side surface of the partition, the partition comprising a thermoelectric element having a low-temperature part and a high-temperature part facing each other with a distance therebetween, an outer peripheral edge extending between the low-temperature part and the high-temperature part, the thermoelectric element being configured to transport heat from the low-temperature part to the high-temperature part, the low-temperature part being in heat exchange contact with the first heat transfer fluid, the high-temperature part being in heat exchange contact with the second heat transfer fluid, and each of the first channel and the second channel comprising a pump for sending the respective heat transfer fluid through the channel.

Description

Technical Field

[0001] The present invention relates to a thermoelectric heat pump.

Background Art

[0002] Known thermoelectric heat pumps are used to transfer heat from a first heat transfer fluid to a second heat transfer fluid. Usually, this transfer is carried out against the temperature gradient existing between the fluids. The thermoelectric elements (also called Peltier elements) used in thermoelectric heat pumps have no moving parts. For this reason, such heat pumps are often used in special applications where it is particularly advantageous that the heat pump is vibration-free and can function without moving parts or liquids.

[0003] However, known thermoelectric heat pumps have the drawback that the achievable efficiency is very low. As a result, existing heat pumps cannot be effectively utilized in applications that require a higher heat capacity, such as residential and industrial heating equipment.

[0004] Therefore, an object of the present invention is to provide a thermoelectric heat pump capable of reducing or eliminating one or more of the above-mentioned drawbacks.

Summary of the Invention

[0005] The above object is achieved by a thermoelectric heat pump comprising a heat exchanger block having a first channel for flowing a first heat transfer fluid such as a liquid medium and a second channel separate from the first channel for flowing a second heat transfer fluid such as a liquid medium, the heat exchanger block comprising a heat exchange cavity including a first sub-cavity and a second sub-cavity fluidly separated by a partition, the first sub-cavity and the second sub-cavity being fluidly connected to the first channel and the second channel respectively, the first heat transfer fluid in the first sub-cavity being in heat exchange contact with a first side surface of the partition, the second heat transfer fluid in the second sub-cavity being in heat exchange contact with a second side surface opposite to the first side surface of the partition, the partition comprising a thermoelectric element having a cold side and a hot side facing each other at a distance, an outer peripheral edge extending between the cold side and the hot side, the thermoelectric element being configured to transport heat energy from the cold side to the hot side, the cold side being in heat exchange contact with the first heat transfer fluid, the hot side being in heat exchange contact with the second heat transfer fluid, and each of the first channel and the second channel comprising a pump for sending the respective heat transfer fluid through the channel.

[0006] By providing a thermoelectric element between the sub-cavities of the heat exchange cavity and pumping the heat transfer fluids in the respective sub-cavities along the partition, an electric current can be passed through the thermoelectric element to transport heat from the first heat transfer fluid to the second heat transfer fluid. Since each heat transfer fluid is pumped separately, the flow rate can be selected while considering the temperature difference (across the thermoelectric element), thereby significantly improving the heat transfer efficiency compared to, for example, a heat pump that does not use moving parts such as pumps. To further enhance the thermal efficiency, it is preferable that the temperature difference across the thermoelectric element be kept relatively low. For this purpose, it is preferable that the temperature difference across the thermoelectric element be kept at 60% or less of the maximum temperature difference achievable by the thermoelectric element.

[0007] It is preferable to use a liquid medium as one or both of the heat media. Examples of the liquid medium include a liquid coolant based on an aqueous solution of potassium formate. This solution is more preferably in a substantially saturated or completely saturated state. Such a coolant is advantageous because it has a low freezing point while its viscosity and specific heat capacity are very close to those of water. Furthermore, it is environmentally friendly and biodegradable.

[0008] Each channel can be fluidly connected to a further heat exchanger within a closed circuit or can also be directly connected to a heat transfer fluid that supplies or releases thermal energy.

[0009] By reversing the direction of the current flowing through the thermoelectric element, the direction of heat transport can be easily reversed. Thereby, the same heat pump can be used for both cooling and heating.

[0010] The thermoelectric element can be configured as a single-layer thermoelectric element or can also have a cascade structure of two or more thermoelectric sub-elements. By connecting the thermoelectric sub-elements in series, a large temperature difference can be obtained between the first heat transfer fluid and the second heat transfer fluid while suppressing the temperature difference across a single thermoelectric sub-element.

[0011] In one embodiment of the heat pump according to the present invention, the first side surface and the second side surface of the partition are respectively formed by the low-temperature part and the high-temperature part of the thermoelectric element that are in direct heat exchange contact with the respective heat transfer fluids. The thermoelectric element is attached to the heat exchanger block in a sealed state over the entire outer peripheral edge by a flexible seal that faces only the outer peripheral edge for the purpose of maximizing the heat exchange surfaces of the low-temperature part and the high-temperature part.

[0012] By forming the partition with the thermoelectric element itself, the loss at the transitions where the material switches can be minimized. For this purpose, the thermoelectric element can be coated or surface-treated as needed to limit or prevent permeability to the heat transfer fluid used. It is highly advantageous if the thermoelectric element is mounted within the heat exchange cavity or heat exchanger block so as to seal the entire circumference of the thermoelectric element and the seal portion does not interfere with heat exchange at the heat exchange surface of the thermoelectric element. For this purpose, the seal portion is arranged only at the outer peripheral edge of the thermoelectric element so that the entire heat exchange surface can be in direct contact with the respective heat medium. By giving flexibility to the seal portion, the thermal contraction and expansion of the thermoelectric element can be absorbed, preventing excessive mechanical stress from being applied to the element.

[0013] In another embodiment of the heat pump according to the present invention, the partition has a film on each side of the thermoelectric element, and these films form the first side and the second side of the partition respectively. Between the film and the side of each adjacent thermoelectric element, a non-curing thermally conductive paste is arranged so as to be able to absorb the thermal contraction and expansion of the thermoelectric element with respect to the film.

[0014] Since the thermoelectric element is located between two films, the mechanical stress on the element due to the pressure difference between the sub-cavities can be absorbed through the films. As a result, the lifespan of the thermoelectric element is significantly improved. This film also functions as an impermeable hermetic seal that does not allow fluid to pass through. A thermally conductive paste is supplied between the thermoelectric element and the film for the purpose of reducing the heat transfer loss between the materials. By applying a non-curing paste, the thermoelectric element can contract and / or expand without being subjected to mechanical stress due to mutual friction. Therefore, the thermoelectric element is not firmly fixed between the two films but is merely surrounded by the two films, and relative movement between the thermoelectric element and the films is possible. This paste functions not only as a heat conductor but also as a mechanical buffer and lubricant.

[0015] In a preferred embodiment of the heat pump according to the present invention, the outer peripheral edge of the thermoelectric element is separated from other members over the entire circumference (not in contact with other members and is released).

[0016] When the outer peripheral edge of the thermoelectric element is open over the entire circumference (clear), the thermoelectric element is completely separated from other members, and the mechanical stress applied to the element is reduced to the maximum extent. As a result, the long life of the thermoelectric element is realized.

[0017] Another embodiment of the heat pump according to the present invention is a heat pump in which the heat exchange surfaces on the first side and the second side of the partition are larger than the heat exchange surfaces on each side of the thermoelectric element, and the entire heat exchange surfaces on both sides of the thermoelectric element face the heat exchange surfaces on each side of the partition and are preferably located at the center of the heat exchange surfaces on each side of the partition.

[0018] By opposing the entire heat exchange surfaces on both sides of the thermoelectric element to the respective membranes forming the partition, it is possible to prevent the generation of thermal stress in the element or in the heat exchange surface of the element due to non-uniform heat transfer. The thermoelectric element is preferably arranged at the center with respect to the partition. As a result, uniform heat transfer is obtained, and a space is formed along the edge of the partition where a seal portion can be arranged without disturbing heat exchange.

[0019] Still another embodiment of the heat pump according to the present invention is a heat pump in which the flow of the heat transfer fluid in the sub-cavity is laminar and is uniformly distributed on the heat exchange surface of the partition.

[0020] By forming a laminar flow in the sub-cavity, the flow of the liquid can be distributed highly uniformly and homogeneously across the partition. As a result, on the one hand, heat transfer is improved, and on the other hand, the surface temperature of the partition becomes highly homogeneous, and thermal stress can be further suppressed. In order to improve heat transfer, micro-vortices can be generated in the partition. In this case, the flow in the sub-cavity is substantially laminar, but turbulent flow occurs on the heat exchange surface.

[0021] Another embodiment of the heat pump according to the present invention is a heat pump including at least two thermoelectric layers between a low-temperature part and a high-temperature part.

[0022] By applying a cascade of two or more thermoelectric layers or thermoelectric sub-elements, it becomes possible to achieve a large temperature difference between the low-temperature part and the high-temperature part of the thermoelectric element while keeping the temperature difference across a single thermoelectric layer small. The plurality of thermoelectric layers function as a series of steps in the heat transfer direction (steps of sequentially transferring heat). Therefore, it becomes possible to further optimize the operating range of the thermoelectric layer.

[0023] Yet another embodiment of the heat pump according to the present invention is a heat pump in which an intermediate film is disposed between two adjacent thermoelectric layers.

[0024] By applying the intermediate film, it is possible to absorb the thermal contraction and / or expansion of two adjacent thermoelectric layers. It is preferable to dispose a thermally conductive paste between the thermoelectric layer and the intermediate film. As the intermediate film, for example, a copper layer can be used. The intermediate film can also function as a thermal buffer and can achieve a uniform distribution of heat.

[0025] In yet another embodiment of the heat pump according to the present invention, at least one of two adjacent thermoelectric layers is composed of a plurality of thermoelectric sub-elements, and preferably, is composed of more thermoelectric sub-elements than the other adjacent thermoelectric layer.

[0026] Since the intermediate film also conducts heat, the intermediate film is also used to conduct heat from a plurality of parallel thermoelectric sub-elements forming part of the thermoelectric layer to an adjacent layer. A further advantage is that when one thermoelectric sub-element fails, its heat can be conducted through the thermally conductive intermediate film to another sub-element that is still operating.

[0027] These layers can also be composed of different numbers of thermoelectric sub-elements arranged in parallel. Therefore, even when the characteristics of different layers do not directly correspond, thermoelectric sub-elements with characteristics suitable for each layer can be selected for each layer.

[0028] Also, one embodiment of the heat pump according to the present invention is a heat pump in which the sizes of the heat exchange surfaces of at least two thermoelectric layers are substantially the same.

[0029] By making the sizes of the heat exchange surfaces of the thermoelectric layers substantially the same, a compact structure can be obtained in which the heat exchange surface in the low-temperature part corresponds to the heat exchange surface in the high-temperature part. The heat generation amount in the high-temperature part of the thermoelectric element can be adjusted by changing the flow rate of the second heat transfer fluid, thereby preventing heat saturation of the thermoelectric layer particularly close to the high-temperature part.

[0030] In yet another embodiment of the heat pump according to the present invention, the heat pump includes a housing having a plurality of heat exchanger blocks, and the housing includes a first manifold for fluidly connecting the first channels of the plurality of heat exchanger blocks to each other, and a second manifold for fluidly connecting the second channels of the plurality of heat exchanger blocks to each other.

[0031] By arranging a plurality of heat exchanger blocks in the housing, the capacity of the heat pump can be easily increased. The housing functions here as a manifold for fluidly connecting the heat exchanger blocks. A plurality of heat pumps can also be arranged in series or in parallel.

[0032] Also, a pair of heat exchanger blocks can be joined such that the second sub-cavity is shared between the two heat exchanger blocks.

[0033] Another embodiment of the heat pump according to the present invention is a heat pump in which the heat exchanger blocks are thermally insulated from each other.

[0034] By thermally insulating the heat exchanger blocks from each other, undesirable losses can be prevented. This insulation can be achieved, for example, by means of an intermediate air chamber or heat insulating material. It is also possible to further insulate the entire housing.

Brief Description of the Drawings

[0035] These and other features of the present invention will be further described with reference to the accompanying drawings.

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0036] Figure 1 shows a schematic cross-section of an embodiment of the heat exchanger block 1 of the heat pump according to the present invention. The first channel (first flow path) 2 and the second channel (second flow path) 3 are each fluidly separated from each other and are each fluidly connected to the first sub-cavity 4 and the second sub-cavity 5, respectively. The directions of the flows in the two sub-cavities 4, 5 are indicated by arrows, but the relative directions of the flow directions can also be changed. The partition 6 separates the first sub-cavity 4 from the second sub-cavity 5. A thermoelectric element 7 is arranged on this partition 6. The element 7 is arranged between the first film 8 and the second film 9 and transports thermal energy in the direction of arrow 10, that is, from the first sub-cavity 4 to the second sub-cavity 5. In practice, in many cases, it is selected to arrange the heat exchanger block 1 such that the arrow 10 is in the direction opposite to gravity. Thereby, the upward movement of heat can be optimally utilized. The films 8, 9 fluidly isolate the sub-cavities 4, 5 from each other and are provided with seals 11. The seals 11 are arranged outside the heat exchange surfaces of the films 8, 9 that are in direct contact with the sub-cavities 4, 5. The low-temperature part 12 faces the first film 8, and a thermally conductive paste (not shown) is arranged between them. Similarly, the high-temperature part 13 faces the second film 9, and a thermally conductive paste is arranged between them. Thereby, the element 7 can expand and contract without being subjected to large mechanical stresses. Further, the free space 14 formed around the peripheral part of the element 7 also provides the space necessary for expansion.

[0037] Figure 2 is a cross-sectional view of a second embodiment of the heat pump 20 according to the present invention. In this embodiment, two heat exchanger blocks 21, 22 are combined, and a second sub-cavity 23 is shared by the two heat exchanger blocks 21, 22. The first channels 24, 25 open (debouch) into their respective sub-cavities 26, 27. The membranes 28 seal the sub-cavities 23, 24, 25 and surround their respective thermoelectric elements 29, 30. The operating direction of the first thermoelectric element 29 is opposite to that of the second thermoelectric element 30. The space 31 between the membranes 28 provides space for the expansion of the elements 29, 30. The housing 32 has a manifold 33 formed therein for fluidly connecting the first channels 24, 25 to each other.

[0038] In another interpretation of the cross-section of Figure 2, a third embodiment of the heat pump according to the present invention is shown. In this embodiment, the operating direction of the heat exchanger block 22 is reversed compared to the second embodiment, and the two heat exchanger blocks 21, 22 are connected in series. The second sub-cavity 23 of the first heat exchanger block 21 simultaneously serves as the first sub-cavity 23 of the second heat exchanger block 22. The sub-cavity 23 is fluidly connected to another third channel and is not fluidly connected to the first channel 24 and the second channel 25. It is preferable that a pump is provided in this third channel. Thus, the thermoelectric elements 29, 30 have the same operating direction in this embodiment. The first heat transfer fluid forming the coldest medium flows through the first channel 24. The third heat transfer fluid having an intermediate temperature flows through the sub-cavity 23. The second heat medium having the highest temperature flows through the second channel 25. With this structure, a large temperature difference can be obtained between the first heat transfer fluid and the second heat transfer fluid while keeping the temperature difference (the temperature difference applied to the thermoelectric elements 29, 30) at both ends of each of the thermoelectric elements 29, 30 small. The third heat transfer fluid transports energy between the two thermoelectric elements 29, 30. The third heat transfer fluid is preferably sent by a pump in a turbulent flow.

[0039] Figure 3 is a perspective view of a fourth embodiment of the heat pump 40 according to the present invention. The heat pump 40 includes a supply pipe 41 and a return pipe 42 in the head portion. The supply pipe 41 and the return pipe 42 are each fluidly connected to a supply manifold and a discharge manifold. These manifolds are fluidly connected by a plurality of first channels. A supply pipe 43 and a return pipe 44 are each fluidly connected to the supply manifold and the discharge manifold. These manifolds are fluidly connected by a plurality of second channels. The housing 45 is formed by an assembly of ten double heat exchanger blocks 46 configured as shown in FIG. 2. Each heat exchanger block 46 is provided with electric wires 47, 48 for supplying the current required for the thermoelectric elements.

Claims

1. A thermoelectric heat pump comprising a heat exchanger block having a first channel for flowing a first heat transfer fluid such as a liquid medium and a second channel separate from the first channel for flowing a second heat transfer fluid such as a liquid medium, wherein the heat exchanger block comprises a heat exchange cavity including a first sub-cavity and a second sub-cavity fluidly separated by a partition, and the first sub-cavity and the second sub-cavity are fluidly connected to the first channel and the second channel respectively, wherein the first heat transfer fluid in the first sub-cavity is in heat exchange contact with a first side surface of the partition, and the second heat transfer fluid in the second sub-cavity is in heat exchange contact with a second side surface of the partition opposite to the first side surface, wherein the partition comprises a thermoelectric element having a low temperature part and a high temperature part facing each other at a distance, and an outer peripheral edge extends between the low temperature part and the high temperature part, wherein the thermoelectric element is configured to transport heat from the low temperature part to the high temperature part, the low temperature part is in heat exchange contact with the first heat transfer fluid, and the high temperature part is in heat exchange contact with the second heat transfer fluid, wherein each of the first channel and the second channel comprises a pump for sending the respective heat transfer fluid through the channel, the heat pump.

2. The first side surface and the second side surface of the partition are respectively formed by the low temperature part and the high temperature part of the thermoelectric element in direct heat exchange contact with the respective heat transfer fluids, The thermoelectric element is attached to the heat exchanger block in a sealed state over the entire circumference of the outer peripheral edge by a flexible seal facing only the outer peripheral edge for the purpose of maximizing the heat exchange surfaces of the low temperature part and the high temperature part, the heat pump according to claim 1.

3. The partition comprises a film on each side of the thermoelectric element, and these films form the first side surface and the second side surface of the partition respectively, A non-curing thermally conductive paste is disposed between the film and the side of each adjacent thermoelectric element so as to be able to absorb thermal contraction and expansion of the thermoelectric element with respect to the film, the heat pump according to claim 1.

4. The outer peripheral edge of the thermoelectric element is separated from other members over the entire circumference, the heat pump according to claim 3.

5. The heat exchange surfaces of the first side and the second side of the partition are larger than the heat exchange surfaces on each side of the thermoelectric element, and the entire heat exchange surfaces on both sides of the thermoelectric element face the heat exchange surfaces of the respective sides of the partition and are preferably located at the center of the heat exchange surfaces of the respective sides of the partition. The heat pump according to claim 3 or 4.

6. The flow of the heat transfer fluid in the first sub-cavity and the second sub-cavity is laminar and is uniformly distributed on the heat exchange surface of the partition. The heat pump according to any one of claims 1 to 5.

7. The heat pump according to any one of claims 1 to 6, comprising at least two thermoelectric layers between the low-temperature part and the high-temperature part.

8. The heat pump according to claim 7, wherein an intermediate film is disposed between two adjacent thermoelectric layers.

9. The heat pump according to claim 8, wherein at least one of the two adjacent thermoelectric layers is composed of a plurality of thermoelectric sub-elements, and preferably is composed of more thermoelectric sub-elements than the other adjacent thermoelectric layers.

10. The heat pump according to claim 7, 8 or 9, wherein the sizes of the heat exchange surfaces of each of the at least two thermoelectric layers are substantially the same.

11. The heat pump according to any one of claims 1 to 10, comprising a housing having a plurality of heat exchanger blocks, and the housing comprises a first manifold for fluidly connecting the first channels of the plurality of heat exchanger blocks to each other, and a second manifold for fluidly connecting the second channels of the plurality of heat exchanger blocks to each other.

12. The heat pump according to claim 11, wherein the plurality of heat exchanger blocks are thermally insulated from each other.

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