Thermoelectric heat pump

Abstract

The invention relates to a thermoelectric heat pump comprising a heat exchanger block having a first channel for the flow of a first heat transfer fluid (e.g., a liquid medium) and a separate second channel for the flow of a second heat transfer fluid (e.g., a liquid medium), the heat exchanger block comprising a heat exchange chamber, the heat exchange cavity is hydraulically divided into a first sub-cavity and a second sub-cavity by a partition, the first sub-cavity and the second sub-cavity are respectively connected to a first channel and a second channel, a first heat transfer fluid in the first sub-cavity is in heat exchange contact with a first side of the partition, and a second heat transfer fluid in the second sub-cavity is in heat exchange contact with a second side of the partition. The second heat transfer fluid in the second sub-cavity is in heat exchange contact with a second side of the separator opposite the first side, where the separator comprises a thermoelectric element having a cold side and a hot side opposite and spaced apart from the cold side, where a peripheral edge extends between the cold side and the hot side, the thermoelectric element is configured to transfer heat from the cold side to the hot side, where the cold side is in heat exchange contact with a first heat transfer fluid, and where the hot side is in heat exchange contact with a second heat transfer fluid, where each channel is provided with a pump for pumping the respective heat transfer fluid therethrough.

Description

Technical Field

[0001] The present invention relates to thermoelectric heat pumps. Background Art

[0002] Known thermoelectric heat pumps are used to transfer heat from a first heat transfer fluid to a second heat transfer fluid, typically against the temperature gradient that prevails between the fluids. Since the thermoelectric elements (also called Peltier elements) employed in thermoelectric heat pumps do not include any moving parts, such heat pumps are often used for special applications where it is particularly advantageous that the heat pump is vibration-free and can operate without other moving parts or liquids.

[0003] However, a disadvantage of known thermoelectric heat pumps is that the efficiency achieved is very low. As a result, existing heat pumps cannot be used effectively for applications requiring a larger thermal capacity, such as residential or industrial heating installations. Summary of the invention

[0004] The object of the present invention is to provide a thermoelectric heat pump whereby one or more of the above-mentioned disadvantages may be reduced or even eliminated.

[0005] This object is achieved by a thermoelectric heat pump according to the present invention, the thermoelectric heat pump comprising a heat exchanger block, the heat exchanger block having a first channel for a first heat transfer fluid (e.g., a liquid medium) to flow through and an independent second channel for a second heat transfer fluid (e.g., a liquid medium) to flow through, wherein the heat exchanger block comprises a heat exchange chamber, the heat exchange chamber being hydraulically divided into a first sub-chamber and a second sub-chamber by a partition, the first sub-chamber and the second sub-chamber being connected to the first channel and the second channel, respectively, wherein the first heat transfer fluid in the first sub-chamber is thermally coupled to a first side of the partition exchange contact, and a second heat transfer fluid in the second subchamber is in heat exchange contact with a second side of the partition opposite to the first side, wherein the partition includes a thermoelectric element, the thermoelectric element having a cold side and a hot side opposite to and at a distance from the cold side, wherein the peripheral edge extends between the cold side and the hot side, the thermoelectric element is configured to transfer thermal energy from the cold side to the hot side, and wherein the cold side is in heat exchange contact with the first heat transfer fluid, and wherein the hot side is in heat exchange contact with the second heat transfer fluid, and wherein each channel is provided with a pump for pumping the corresponding heat transfer fluid through the channel.

[0006] By arranging thermoelectric elements between the sub-cavities of the heat exchange chamber, wherein the heat transfer fluid in the respective sub-cavity is pumped along the partition by a pump, heat can be transferred from the first heat transfer fluid to the second heat transfer fluid by passing an electric current through the thermoelectric elements. Since the respective heat transfer fluids are pumped separately, the flow rate can be selected according to the temperature difference across the thermoelectric elements, so that the heat transfer efficiency can be greatly improved compared to heat pumps without moving parts such as pumps. In order to further improve the thermal efficiency, the temperature difference across the thermoelectric elements is preferably kept relatively low here. For this purpose, the temperature difference across the thermoelectric elements is preferably kept below 60% of the maximum temperature difference that can be achieved by the thermoelectric elements.

[0007] Here, for one or both of the heat transfer fluids, a liquid medium is preferably used, for example a liquid coolant based on an aqueous solution of potassium formate. The solution is more preferably substantially or completely saturated. This coolant is advantageous because it has a lower freezing point, while the viscosity and heat capacity are very similar to those of water. In addition, the solution is environmentally friendly and biodegradable.

[0008] The respective channels can each be hydraulically connected to other heat exchangers in a closed circuit or directly to a heat transfer fluid that supplies or releases thermal energy.

[0009] The direction of heat transfer can be reversed in a simple manner by reversing the direction of the current flowing through the thermoelectric element. This allows the same heat pump to be used for both cooling and heating.

[0010] The thermoelectric element may be in the form of a single layer thermoelectric element, but may also comprise a cascade of two or more thermoelectric elements. Connecting the thermoelectric elements in series enables the temperature difference across a single thermoelectric element to be kept smaller, while still achieving a large temperature difference between the first and second heat transfer fluids.

[0011] In an embodiment of the heat pump according to the invention, the first side and the second side of the partition are formed by the cold side and the hot side, respectively, of a thermoelectric element, which are in direct heat-exchanging contact with a respective heat transfer fluid, and wherein the thermoelectric element is sealingly mounted around the peripheral edge of the heat exchanger block by means of a flexible seal which rests completely against the peripheral edge in order to maximize the heat-exchanging surface of the cold side and the hot side.

[0012] The use of the thermoelectric elements themselves to form the separators can minimize the losses between material transitions. For this purpose, if necessary, the thermoelectric elements can be provided with a coating or surface treatment, which limits or prevents the permeability of the heat transfer fluid used. Here, it is very advantageous to install the thermoelectric elements in a sealed manner around the heat exchange chamber or heat exchanger block so that the seal does not form any obstacle to the heat exchange on the heat exchange surface of the thermoelectric elements. For this purpose, the seal is only arranged against the peripheral edge, so that the entire heat exchange surface is in contact with the corresponding heat transfer fluid. Providing the seal with a flexible form makes it possible to adapt to the thermal contraction and / or expansion of the thermoelectric elements, so that excessive mechanical stresses in the elements can be prevented.

[0013] In an alternative embodiment of the heat pump according to the invention, the separator further comprises a membrane on either side of the thermoelectric element, the membrane forming a first side and a second side of the separator respectively, wherein a non-hardening thermally conductive paste is arranged between the membrane and the respective adjacent sides of the thermoelectric element in order to be able to accommodate thermal contraction and expansion of the thermoelectric element relative to the membrane.

[0014] Encapsulating the thermoelectric element between two membranes enables the mechanical stresses on the element to be adapted via the membrane to the pressure difference between the element chambers. This significantly increases the service life of the thermoelectric element. The membrane can also provide a watertight seal. A thermally conductive paste is provided between the thermoelectric element and the membrane in order to reduce transmission losses between the materials. By applying a non-hardening paste, the thermoelectric element can shrink and / or expand without mechanical stresses being generated by mutual friction. The thermoelectric element is therefore not tightly wedged between the two membranes, but is simply encapsulated by the two membranes, wherein relative movement between the thermoelectric element and the membrane is still possible. The paste can therefore be used not only as a thermal conductor, but also as a mechanical buffer and lubricant.

[0015] In a preferred embodiment of the heat pump according to the invention, there is no shielding around the peripheral edge of the thermoelectric element.

[0016] When there is no shading around the thermoelectric element, the thermoelectric element is completely decoupled and the mechanical stress on the element is minimized. This ensures a long service life of the element.

[0017] Another embodiment of the heat pump according to the invention is a heat pump, wherein the heat exchange surfaces of the first and second sides of the partition are larger than the heat exchange surfaces of the corresponding sides of the thermoelectric element, and wherein the entire heat exchange surfaces of the sides of the thermoelectric element are in contact with the heat exchange surfaces of the corresponding sides of the partition and are preferably centrally located relative to the heat exchange surfaces of the corresponding sides of the partition.

[0018] The entire heat exchange surface on the side of the thermoelectric element is brought to bear against the respective film forming the separator, preventing thermal stresses in the element or in the heat exchange surface of the element due to uneven heat transfer. The thermoelectric element is preferably centrally located relative to the separator, so that a uniform transfer is obtained and also spaces are created along the edges of the separator, on which seals can be arranged without them interfering with the heat exchange.

[0019] A further embodiment of the heat pump according to the invention is a heat pump, wherein the flow of the heat transfer fluid in the subcavities is laminar and evenly distributed over the heat exchanging surface of the partition.

[0020] By providing a laminar flow in the subcavity, a highly uniform and homogeneous distribution of the liquid flow on the partition is obtained. This can improve the transfer efficiency on the one hand and make the surface temperature of the partition more uniform on the other hand, which can further prevent thermal stress. In order to increase the heat transfer, micro-vortices can be generated at the partition, where the flow in the subcavity is essentially laminar, but turbulent at the heat exchange surface.

[0021] A further embodiment of a heat pump according to the invention is a heat pump comprising at least two thermoelectric layers between the cold side and the hot side.

[0022] By using a cascade of two or more thermoelectric layers or thermoelectric elements, the temperature difference across a single thermoelectric layer can be kept smaller, while still achieving a large temperature difference between the cold and hot sides of the thermoelectric element. The thermoelectric layer acts as a continuous step in the direction of heat transfer. The operating range of the thermoelectric layer can therefore be further optimized.

[0023] A further embodiment of the heat pump according to the invention is a heat pump in which an intermediate film is arranged between two adjacent thermoelectric layers.

[0024] Applying the intermediate film enables the thermal contraction and / or expansion of the adjacent thermoelectric layer to be accommodated. The thermally conductive paste is preferably arranged between the thermoelectric layer and the intermediate film. The intermediate film can be, for example, a copper layer. The intermediate film can also act as a thermal buffer and ensure a uniform distribution of heat.

[0025] In a further embodiment of the heat pump according to the invention, at least one of two adjacent thermoelectric layers consists of a plurality of thermoelectric elements, preferably of more thermoelectric elements than the other adjacent thermoelectric layer.

[0026] Since the interlayer also conducts heat, the interlayer can also be used to conduct heat from multiple parallel thermoelectric elements forming part of a thermoelectric layer to adjacent layers. Another advantage is that if a thermoelectric element fails, the heat can be conducted through the conductive interlayer to another subelement that is still in operation.

[0027] These layers can then also optionally be composed of different numbers of thermoelectronic elements arranged in parallel. Thus, even if the properties of the different layers do not directly correspond, thermoelectronic elements with suitable properties can be selected for each layer.

[0028] Furthermore, according to an embodiment of the heat pump the invention the heat exchanging surface of each of the thermoelectric layers is substantially the same.

[0029] By making the heat exchange surfaces of the thermoelectric layers substantially identical, a compact construction can be obtained, wherein the heat exchange surface on the cold side corresponds to the heat exchange surface on the hot side. The heat generation on the hot side of the thermoelectric element can be adjusted here by varying the flow rate of the second heat transfer fluid, so that thermal saturation of the thermoelectric layer close to the hot side can be prevented.

[0030] In a further embodiment of the heat pump according to the invention, the heat pump comprises a housing provided with a plurality of heat exchanger blocks, wherein the housing comprises a first manifold for hydraulically connecting the first channels to one another and comprises a second manifold for hydraulically connecting the second channels of the heat exchanger blocks to one another.

[0031] By arranging a plurality of heat exchanger blocks in a housing, the capacity of the heat pump can be increased in a simple manner. The housing serves here as a manifold for hydraulically connecting the heat exchanger blocks. Several heat pumps can also be selectively placed in series or in parallel.

[0032] It is also possible to couple a pair of heat exchanger blocks so that the second sub-cavity is shared by both heat exchanger blocks.

[0033] A further embodiment of the heat pump according to the invention is a heat pump, wherein the heat exchanger blocks are thermally insulated from one another.

[0034] By thermally insulating the heat exchanger blocks from each other, unnecessary losses can be prevented. For example, the insulation can be obtained by an intermediate air chamber or an insulating material. Optionally, the entire housing can also be further insulated. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0036] Figure 1 is a schematic cross-sectional view of an embodiment of a heat exchanger block of a first embodiment of a heat pump according to the invention.

[0037] Figure 2 is a cross-sectional view of a second embodiment of a heat pump according to the present invention.

[0038] Figure 3 is a perspective view of a third embodiment of a heat pump according to the present invention. DETAILED DESCRIPTION

[0039] Figure 1 A schematic cross section of an embodiment of a heat exchanger block 1 of a heat pump according to the invention is shown. A first channel 2 and a second channel 3 are hydraulically separated from each other and are hydraulically connected to a first subchamber 4 and a second subchamber 5, respectively. In both subchambers 4, 5, the flow direction is indicated by arrows, but different relative orientations of the flow directions can also be chosen. A partition 6 separates the first subchamber 4 from the second subchamber 5. A thermoelectric element 7 is arranged in the partition 6. The element 7 is arranged between a first membrane 8 and a second membrane 9 and transfers thermal energy in the form of heat in the direction of an arrow 10, thus from the first subchamber 4 to the second subchamber 5. In practice, it is usually chosen to orient the heat exchanger block 1 so that the arrow 10 is opposite to the gravity, so that the heat rise can be optimally utilized. The membranes 8, 9 hydraulically close the subchambers 4, 5 from each other and are provided with a seal 11. The seal 11 is arranged on the outside of the heat exchange surface of the membranes 8, 9 that is in direct contact with the subchambers 4, 5. The cold side 12 rests on the first membrane 8, and a heat-conducting paste (not shown) is arranged between the transitions. The hot side 13 is in contact with the second film 9, and a heat-conducting paste is also arranged on this transition. This allows the element 7 to expand and contract without being subjected to great mechanical stress. The free space 14 formed around the peripheral edge of the element 7 also provides the space required for expansion.

[0040] Figure 2 A cross-sectional view of a second embodiment of a heat pump 20 according to the present invention is shown. In this embodiment, two heat exchanger blocks 21, 22 are combined together, wherein the second sub-cavity 23 is shared by the two heat exchanger blocks 21, 22. The first channels 24, 25 lead into the respective sub-cavities 26, 27. The membrane 28 seals the sub-cavities 23, 24, 25 and encapsulates the respective thermoelectric elements 29, 30. The running direction of the first thermoelectric element 29 is opposite to the running direction of the second thermoelectric element 30. The empty space 31 between the membranes 28 provides space for the expansion of the elements 29, 30. A manifold 33 is formed in the housing 32, which hydraulically connects the first channels 24, 25 to each other.

[0041] exist Figure 2In another illustration of the cross section of , a third embodiment of the heat pump according to the present invention is shown. In this embodiment, the running direction of the heat exchanger block 22 is opposite to the second embodiment, whereby the two heat exchanger blocks 21, 22 are connected in series. The second sub-chamber 23 of the first heat exchanger block 21 simultaneously forms the first sub-chamber 23 of the second heat exchanger block 22. The sub-chamber 23 is hydraulically connected to an independent third channel, which is not hydraulically connected to the corresponding first channel 24 and the second channel 25. The third channel is preferably also provided with a pump. Therefore, in this embodiment, the thermoelectric elements 29, 30 have the same running direction. The first heat transfer fluid forming the coldest medium flows in the first channel 24. The third heat transfer fluid with an average temperature flows in the sub-chamber 23. The second heat transfer fluid with the highest temperature flows in the second channel 25. Due to this structure, the temperature difference on the corresponding thermoelectric elements 29, 30 can be kept low and a large temperature difference between the first heat transfer fluid and the second heat transfer fluid can still be achieved. The third heat transfer fluid transmits energy between the two thermoelectric elements 29, 30. The third heat transfer fluid is preferably pumped in a turbulent manner.

[0042] Figure 3 A perspective view of a fourth embodiment of a heat pump 40 according to the invention is shown. The heat pump 40 is provided at the head with a supply duct 41 and a return duct 42, which are hydraulically connected to a supply manifold and a discharge manifold, respectively, which are hydraulically connected by a first channel. A supply duct 43 and a return duct 44 are hydraulically connected to a supply manifold and a discharge manifold, respectively, which are hydraulically connected by a second channel. A housing 45 is formed by an assembly of ten double heat exchanger blocks 46, which are composed as follows Figure 2 Each heat exchanger block 46 is provided with electric wires 47, 48 for supplying the required current to the thermoelectric element.

Claims

1. A thermoelectric heat pump comprising a heat exchanger block having a first channel for a first heat transfer fluid, such as a liquid medium, to flow through and a separate second channel for a second heat transfer fluid, such as a liquid medium, to flow through, wherein: The heat exchanger block comprises a heat exchange chamber, which is hydraulically divided into a first sub-chamber and a second sub-chamber by a partition, the first sub-chamber and the second sub-chamber being connected to the first channel and the second channel respectively, wherein the first heat transfer fluid in the first sub-chamber is in heat exchange contact with a first side of the partition, and the second heat transfer fluid in the second sub-chamber is in heat exchange contact with a second side of the partition opposite to the first side, wherein the partition comprises a thermoelectric element, the thermoelectric element having a cold side and a hot side opposite to and at a distance from the cold side, wherein a peripheral edge extends between the cold side and the hot side, the thermoelectric element is configured to transfer heat from the cold side to the hot side, and wherein the cold side is in heat exchange contact with the first heat transfer fluid, and wherein the hot side is in heat exchange contact with the second heat transfer fluid, and wherein each channel is provided with a pump for pumping the corresponding heat transfer fluid through the channel.

2. The heat pump according to claim 1, wherein: The first side and the second side of the separator are formed by the cold side and the hot side of the thermoelectric element, respectively, which are in direct heat exchange contact with a corresponding heat transfer fluid, wherein the thermoelectric element is sealingly mounted around the peripheral edge of the heat exchanger block by a flexible seal that is completely in abutment against the peripheral edge in order to maximize the heat exchange surface of the cold side and the hot side.

3. The heat pump according to claim 1, wherein: The separator also includes a film located on either side of the thermoelectric element, the film forming a first side and a second side of the separator respectively, and wherein a non-hardening thermally conductive paste is arranged between the film and the corresponding adjacent sides of the thermoelectric element to accommodate thermal contraction and expansion of the thermoelectric element relative to the film.

4. The heat pump according to claim 3, wherein: The outer peripheral edge of the thermoelectric element is not blocked.

5. The heat pump according to claim 3 or 4, wherein: The heat exchange surfaces on the first and second sides of the separator are larger than the heat exchange surfaces on the corresponding sides of the thermoelectric element, and wherein the entire heat exchange surface on the side of the thermoelectric element is in contact with the heat exchange surface on the corresponding side of the separator and is preferably located centrally relative to the heat exchange surface on the corresponding side of the separator.

6. A heat pump according to any one of the preceding claims, wherein: The flow of the heat transfer fluid in the sub-cavities is laminar and evenly distributed over the heat exchange surface of the partitions.

7. A heat pump according to any one of the preceding claims, comprising at least two thermoelectric layers between the cold side and the hot side.

8. The heat pump according to claim 7, wherein: An intermediate film is arranged 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 elements, preferably more thermoelectric elements than the other adjacent thermoelectric layer.

10. A heat pump according to claim 7, 8 or 9, wherein: The heat exchanging surface of each of the thermoelectric layers is substantially the same.

11. A heat pump according to any one of the preceding claims, comprising a housing provided with a plurality of heat exchanger blocks, wherein: The housing includes a first manifold for hydraulically connecting the first channels to each other, and includes a second manifold for hydraulically connecting the second channels of the heat exchanger blocks to each other.

12. The heat pump according to claim 11, wherein: The heat exchanger blocks are thermally insulated from one another.

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