MXPA98004795A - Heat exchanger device for an air conditioning system - Google Patents

Abstract

A heat exchanger device for an air conditioning system is described, especially for automobiles or other vehicles, comprising first and second heat exchanger elements (30, 31), which define first and second passages (32, 33) of flow, separated, for the medium that transforms heat. Thermoelectric units (45) such as Peltier elements, are arranged between and have opposite heating and cooling surfaces in heat conduction contact with the first and second heat exchanger elements respectively. Each of the heat exchanger elements (30, 31) defines a passage (32, 33) of tortuous flow therein, having a length that is several times the maximum dimension of the heat exchanger element or a plurality of separate coextensive flow passages, each having a small cross-sectional area. Each flow passage (32, 33) is preferably a channel or slit formed in a side surface of the heat exchanger element (30, 31) and this side surface and the channels formed therein can be covered by a plate of cover (43, 44). The thermoelectric units (45) can then be arranged between the cover plates (43, 44) of the first and second heat exchanger elements (30, 3).

Description

HEAT EXCHANGER DEVICE FOR TJN AIR CONDITIONER SYSTEM Description of the invention The present invention describes a heat exchanger device for an air conditioning system, especially for conditioning the air in car cabins or other vehicles. Automotive air-conditioning systems comprising thermoelectric cooling units are described in U.S. Patent No. 3,236,056 and in published Swedish Patent Application No. 8704395. The air-conditioning systems described in these documents comprise one or more thermoelectric units, which are sandwiched between straight water conduits having a rectangular cross section and forming part of heat transfer circuits. The known air conditioning systems have a relatively small cooling capacity and this may be the reason why the documents do not mention anything with respect to the source of electrical energy, which has to be provided to the thermoelectric units of the system. It is assumed that this power source is obviously the standard battery and electricity supply system already available in a car REF: 27771 existing standard in which the air conditioning system will be installed. The object of the present invention is to provide a heat intercalator device for an air conditioning system of the above type, by means of which the capacity and / or efficiency of the air conditioning system can be substantially increased. The heat exchanger device according to the present invention comprises first and second heat exchanger elements defining first and second flow passages separated therefrom for the heat transport medium and a thermoelectric unit, such as the so-called element of Peltier, arranged between and having opposite heating and cooling surfaces in heat conduction contact with the first and second heat exchanger elements, respectively and the heat exchanger device according to the invention is characterized in that a plurality of thermoelectric units arranged in side-by-side relationship are sandwiched between the heat exchanger elements and in that each heat exchanger element defines a tortuous flow passage therein, having a length that is several times the maximum dimension of the exchanger element of heat or a plurality of flu passages separate coextensive elements each having a small cross-sectional area. The heat exchanger device according to the invention can ensure efficient cooling of the hot sides of the thermoelectric units and efficient heating of the cold sides of these units, whereby the overall thermal efficiency of the conditioning system can be increased of air. In addition, the capacity of the air conditioning system can be adapted to that desired by using an appropriate number of thermoelectric units and by sizing the heat exchanger device accordingly. The flow passages formed in any of the heat exchanger elements may comprise two or more tortuous coextensive flow passages or a plurality of substantially straight flow passages extending in the longitudinal direction of the heat exchanger. As an example, each heat exchanger element may define one or a few separate tortuous flow passages substantially covering the contact area of the thermoelectric units or a plurality of separate adjacent flow passages extending in the longitudinal direction of the heat exchanger element. hot. In order to obtain substantially the same effect, the total cross-sectional area or areas of the passage or flow passages must be substantially the same in any case. The thermoelectric units may be, for example, of the type marketed by Marlow Industries Inc., such as Model SP1996. In principle, the heat exchanger device can have any suitable shape that allows the selected number of thermoelectric units to be sandwiched between the elements of the heat exchanger. However, in the preferred embodiment, the heat exchanger element has a flat, block-like shape to allow a maximum number of thermoelectric units to be included in the heat exchanger device in relation to the total volume of this device. The elements of the heat exchanger may have any suitable shape in plan view. However, each heat exchanger element is preferably elongated and can be, for example, rectangular. It has been found that the efficiency of the heat exchanger is improved when the maximum longitudinal dimension of each element and, consequently, of the heat exchanger device substantially exceeds the maximum transverse dimension of the element or device. Thus, the longitudinal length or dimension may be approximately twice the transverse dimension or wide or greater. The best efficiency or performance coefficient of the heat exchanger device is obtained when the cross-sectional area of the passage or flow passages (when each heat exchanger element defines two or more separate coextensive passages) and the area of the element that it comes in contact with thermoelectric units or Peltier elements is between 0.4 x 10 ~ 3 and 0.2 and preferably between 1 x 10 ~ 3 and 40 x 10 ~ 3. In the currently preferred mode, the ratio is between 2.5 x 10 ~ 3 and 8. 5 x 10-3. The tortuous flow passage can be made, for example, in a block-shaped metal sample by drilling and by plugging some of the open ends of the perforated passages. However, preferably the flow passage in at least one of the first and second heat exchanger elements is a channel or slit formed in a side surface of the element. The lateral surface on which the channel or slit is formed can then be appropriately covered or closed, for example, by a film or a sheet, to form the tortuous flow passage. The straight flow passages can be made in the same manner or by extrusion of the heat intercalator element. In a preferred embodiment, the first, also as the second flow passages are channels or slits formed in the opposite adjacent side surfaces of the first and second heat exchanger elements. The channel or slit in each heat exchanger element can then be covered by a plate or cover sheet sealed to the element at least along the contour of the element. The plate-like thermoelectric unit or Peltier element can then be arranged between the cover plates of the first and second heat exchanger elements, for example, by means of a paste or heat-conducting adhesive. Alternatively, or additionally, the heat exchanger elements can be held together by releasable mechanical fastening means, such as screws or bolts, whereby an optimum specific contact pressure can be set between the heat exchanger elements and the units. Thermoelectric devices sandwiched between them. The tortuous flow passages defined in the heat exchanger elements can have any desired shape to ensure good heat transfer between the heat transport medium, usually water or an aqueous liquid, flowing through the flow passages. and the adjacent side surfaces of the thermoelectric units. However, preferably at least one of the first and second flow passages defines one or more meander configurations which have been found to be especially efficient. Each of the flow passages defined by the heat intercalator elements has an inlet and an outlet which can be located at any appropriate position of the element. Preferably, each of the heat exchanger elements has the inlet, also as the outlet, arranged at the same end. Thus, the first heat exchanger element may have its inlet and outlet positioned at one end while the first element may have its inlet and outlet positioned at the opposite end of the heat exchanger device. In such a case, each of the circuits of the air conditioning system for the heat transport medium has to be connected only to one end of the heat exchanger device. Each of the heat exchanger elements may have a substantially rectangular contour and the flow passage defined in each element may then comprise a meander-shaped flow passage section extending transversely at each end of the heat exchanger element interconnected by a longitudinally extending meander flow passage section. This configuration of the flow passage has proven to be especially efficient. The heat exchanger device according to the invention can have any desired size and shape, such that any desired number of thermoelectric units or Peltier elements can be sandwiched between the heat exchanger elements. Consequently, any desired cooling capacity of an air conditioning system including the heat exchanger can be obtained. When the heat exchanger device comprises a plurality of thermoelectric units or Peltier elements, these thermoelectric units are preferably divided into a variety of groups, the thermoelectric units of each group are electrically connected in series and the groups of thermoelectric units are electrically connected, in a mutual way, in parallel. This arrangement has the advantage that in the event that a thermoelectric unit belonging to one of the groups breaks only that group to which it belongs, it becomes inefficient. Although the thermal efficiency of an air conditioning system including the heat exchanger device according to the invention is rather high, the standard power supply system in a standard car is usually not sufficient to supply the electric power, also to the thermoelectric units of the heat exchanger device in cases where a good cooling capacity is required. Accordingly, electric power can be supplied to the thermoelectric units of the heat exchanger device from a separate electrical supply system that includes a current generator driven by the engine of the vehicle to which the air is conditioned. In order to obtain maximum performance of the thermoelectric units, the heat transport capacity of the fluid flowing in the flow passage adjacent to the hot sides of the thermoelectric units must substantially exceed the heat transport capacity of the flowing medium in the flow passage adjacent to the cold side of the thermoelectric units. This can be obtained for example, by means of a heat exchanger device, formed by three superposed heat exchanger elements, the flow passages formed in the external elements are interconnected. Then, the thermoelectric units can be arranged between the internal heat exchanger element and any of the external elements, in such a way that the hot sides of the thermoelectric units are in contact with the external elements as long as the cold sides are in contact with the internal heat exchanger element. However, in the preferred embodiment, the heat exchanger device comprises only a pair of heat exchanger elements and the length of the flow passage adjacent to the hot sides of the thermoelectric units may then be longer than those of the others flow passages adjacent to the cold side of the thermoelectric units. The heat exchanger elements must be manufactured from a material with good thermal conduction characteristics. Thus, the first and second heat exchanger elements are preferably manufactured from aluminum, copper and / or from alloys thereof. The present invention further provides a system for conditioning the air in a space, such as a cab of a vehicle, such system comprises a heat exchanger device according to the invention as described above, the first and second passages of the device of Heat exchanger are included in the first and second closed liquid circuits, respectively, each liquid circuit includes a radiator and means for circulating the liquid therethrough. One of these radiators can be arranged inside and another arranged outside the space in which the air will be conditioned. When the air conditioning system is used to condition the air of a vehicle cabin, one of the liquid circuits may include part of the liquid cooling system of a combustion engine for driving the vehicle. The radiator in the cabin can then be selectively supplied with hot water from the drive motor or with cold water from the heat exchanger device. The invention will now be further described with reference to the drawings, wherein Figure 1 illustrates schematically an air conditioning system according to the invention, for use in a car, Figure 2 is a top plan view of a heat exchanger device shown on an enlarged scale, the Figure 3 is a longitudinal sectional view along the line III-III shown in Figure 2, Figure 4 is a cross-sectional view along the line IV-IV in Figure 2, Figures 5 and 6 are plan views showing the passages for the liquid formed in the heat exchanger device elements shown in Figures 2-4, and Figure 7 schematically illustrates a modified embodiment of the system shown in Figure 1. Figure 1 illustrates schematically an air conditioning system which has been installed in a standard car having a driving engine 10. The motor 10 drives an extra current generator 11, which supplies current to an electrical circuit 12 which comprises an on-off switch 13, a pair of relays 14, a pair of fuses 15, and an ignition switch 16. The heating system of the automobile or car cabin comprises a closed circuit of cooling water 17 including the cooling jacket of the engine 10 and a radiator 18, which is arranged inside the car cabin and which is associated with a fan or fan 19. The air inside the car cabin can be heated in a conventional manner by controlling the fan 19 and the flow of the hot cooling water flowing through the radiator 18. A second water circuit 20 for water cooled includes a water pump 21 and a solenoid valve 22 is connected separately from the water circuit 17 to include the radiator 18 of the car. The second water circuit 20 also includes a passage for the cold flow of a heat exchanger device 23 illustrated in Figures 2-6 and described further below. The air conditioning system shown in Figure 1 further comprises a third liquid closed circuit 24 comprising a hot flow passage of the heat exchanger device 23, a circulation pump 25, a radiator 26 arranged to the outside of the cabin of the automobile and having a fan or associated fan 27, and a tank 28 for the expansion of the liquid. The radiator 18 of the cab can be disconnected from the water jacket of the engine 10 by means of the solenoid valves 29. The heat exchanger device 23 will now be described in more detail. The device 23 comprises a pair of plate-like elements 30 and 31 made of metal, such as aluminum. A tortuous groove or channel 32 and 33, respectively, is formed on a lateral surface of each of the elements 30 and 31. The channel 32 formed in the element 30 comprises a section 34 of meander-shaped channel, arranged at one end of the substantially rectangular element 30, a corresponding meander-shaped channel section 35 arranged at the opposite end of the element and a longitudinally extending, interconnected meander-shaped channel section 36.

The end channel section 35 is connected to a liquid inlet 37 and the end section 34 of the channel is connected to a liquid outlet 38 via a longitudinally extending straight channel segment 39. Through holes 40 are positioned along the periphery of the element 30 and through holes 41 are positioned along the center line of the element. A circumferential groove 42 for receiving a seal or sealing ring is formed outside the channel sections 34-36 and 39. Apart from the fact that the overall length of the channel 33 in the plate-like element 31 is substantially larger that the total length of the channel 32 in the element 30, the elements 30 and 31 are similar. Accordingly, the reference numbers used of Figure 6 are the same as those of Figure 5. However, in Figure 6 a mark has been added to the reference numbers. The channels or slits 32 and 33 in each of the plate-like elements 30 and 31, respectively, are covered by a thin heat-conducting cover plate 43 and 44, respectively, and each of the cover plates is in sealing engagement by a gasket or sealing ring positioned in the slots 42 and 42 'of the gasket, respectively. As shown in Figures 3 and 4, an array of a plurality of plate-like Peltier elements 45 are sandwiched between the cover plates 43 and 44 to substantially cover the total area within the joint gap 42. The elements 30 and 31 with their cover plates 43 and 44 with the Peltier elements 45 arranged therebetween are held together by means of bolts 46 or similar releasable fastening means extending through the aligned holes or perforations 40, 40 'and 41, 41. The Peltier elements are preferably of the type marketed by Marlow Industries Inc., Model SP1996.The heat exchanger device may include, for example, twelve Peltier elements which can be divided into six groups that each includes a pair of elements connected in series Each of the six groups of Peltier elements can be mutually connected in parallel in the current supply circuit 12, in such a way that the plate-like element 30 is positioned on top of the other. cooling side of the Peltier elements 45 while the plate-like element 31 is positioned on the heating side of the Peltier elements. is or meander-like grooves 32 and 33 shown in Figures 5 and 6 can be replaced by a plurality of separate, substantially parallel, straight channels or grooves extending in the longitudinal direction of each of the elements. In such a case, the cross-sectional area of each channel or slit as shown in Figure 4 would be substantially smaller. When the channels or slits are straight, each element 30 and 31 and the corresponding cover plate 43 or 44, can be formed by extrusion as a coherent part. The heat exchanger device 23 is preferably thermally insulated and supported by damper means. The heat insulating means can be for example, foamed plastic, which also functions as a shock absorber. The air conditioning system, illustrated in Figure 1, operates as follows. When the on-off switch 13 is in its off position, the solenoid valves 29 are open while the valve 22 is closed. In this state, the car radiator 18 and the fan 19 can heat the air in the car cabin in a conventional manner. When the switch 13 is moved to its ignition position, the valves 29 close as the valve 22 opens and an electric current is supplied or fed to the Peltier elements 45 of the heat exchanger device 23, to the pumps 21 and 25 and to the fan 27. The water, in the second water circuit 20 will now be made to circulate through the flow passage defined by the channel 32 in the heat exchanger device 23 whereby the water it will be cooled efficiently by the Peltier elements 45 in a manner known per se. The cold water flowing through the radiator 18 of the cabin will now cool the cabin air as it is circulated in the cabin by means of the fan 19. At the same time, the hot side of the Peltier elements 45 will be cooled by the water or another liquid circulated in the third water circuit 24, which includes the channel 33 of the heat exchanger device 23, by means of the pump 25. The heat removed from the heat exchanger device 23 will be released to the outside air via the outdoor radiator 26. In the air conditioning system shown in Figure 7, parts similar to those shown in Figure 1 are indicated by the same reference numerals. In the embodiment shown in Figure 7, the second water circuit has been made independent of the cooling water circuit 17 and comprises a radiator 47 arranged arranged opposite the fan 19 and a tank 48 of liquid expansion. In addition, the operation of the various electrical devices of the system is controlled by an electric control unit 49. It will be appreciated that the air conditioning system shown in Figure 7 can be installed in a car without interfering with the existing electrical and cooling systems of the automobile.

EXAMPLE A heat exchanger device such as that illustrated in Figures 2-6 has a length of 330 mm, a width of 152 mm and a total thickness of 51 mm. The dimensions of the cross section of the channel 32 in the plate-like element 30 is 9 x 14 mm, while the dimensions of the cross section of the channel 33 in the plate-like element 31 are 6 x 14 mm. The heat exchanger device contains twelve Peltier elements model SP1996 from Marlow Industries Inc. These elements are divided into six pairs which are mutually connected in parallel while each pair is connected in series. During cooling from a temperature in the car cabin substantially higher than the ambient temperature, the device is in operation at an electric direct current of 42.1 amps at a voltage of 27.2 volts which is fed to the Peltier elements. Thus, the energy consumption is 1145 W / h. Water or water containing glycol is circulated in circuits 20 and 24 and through associated channels or slits 32, 33 of the heat exchanger device. The flow rate through the channels 32 on the cold side of the Peltier elements is 6 liters / minute at a pressure of 0.6 - 0.6 bar. The cooling speed of the cabin by means of the radiator 18 corresponds to 1000 W / h. The liquid is forced through the liquid circuit 24 which includes the channels 33 by means of the pump 25 at a speed of 6 liters / minute at a pressure of 0.6 -0.8 bars. The coefficient of performance of the system can be calculated as follows: 1000 W x 100 - 87.4% 1145 W It is noted that, in relation to this date, the best known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates. Having described the invention as above, property is claimed as contained in the following

Claims (20)

1. Claims 1. A heat intercalator device for an air conditioning system, the heat exchanger device comprising first and second heat exchanger elements defining first and second separate flow passages for the medium conveying the heat and a thermoelectric unit, arranged between and having opposite heating and cooling surfaces, in heat conducting contact with the first and second heat exchanger elements, respectively, characterized in that a plurality of thermoelectric units, arranged in side-by-side relationship are sandwiched between the heat exchanger elements and because each heat exchanger element defines a tortuous flow passage therein, having a length that is several times the maximum dimension of the heat exchanger element or a plurality of passages of separate coextensive flow, each having a small cross section area. The heat exchanger device according to claim 1, characterized in that each heat exchanger element has a flat, block-like shape. 3. The heat exchanger device according to claim 1 or 2, characterized in that each heat exchanger element has an elongated shape, preferably substantially rectangular. 4. The heat exchanger device according to claim 3, characterized in that the maximum longitudinal dimension of each heat exchanger element substantially exceeds the maximum transverse dimension thereof. 5. A heat exchanger device according to any of claims 1-4, characterized in that the ratio between the cross-sectional areas of the flow passage or the sum of the cross-sectional areas of the flow passages, and the Surface areas of the heat exchanger that are in contact with the thermoelectric units is between 0.4 x 10 ~ 3 and 0.2 and preferably between 1 x 10 ~ 3 and 40 x 10-3. 6. A heat exchanger according to claim 5, characterized in that the ratio is between 2.5 x 10 ~ 3 and 7.5 x 10 ~ 3. The heat exchanger device according to any of claims 1-6, characterized in that the flow passage in at least one of the first and second heat exchanger elements consists of a channel or slit formed in a surface lateral of the element. The heat exchanger device according to claim 7, characterized in that the first and second flow passages are channels or slits formed in the opposite adjacent side surfaces of the first and second heat exchanger elements. The heat exchanger device according to claim 7 or 8, characterized in that the channel or slit in each heat exchanger element is covered by a cover plate sealed to the element along the contour of the element. The heat exchanger device according to claim 8 and 9, characterized in that the plate-like thermoelectric units are arranged between the cover plates of the first and second heat exchanger elements. 11. The heat exchanger device according to any of claims 1-10, characterized in that the heat exchanger elements are held together by releasable fastening means, such as screws or bolts. 12. The heat exchanger device according to any of claims 1-11, characterized in that at least one of the first and second flow passages defines one or more meander-shaped configurations. 13. The heat exchanger device according to any of claims 1-12, characterized in that the flow passage of each heat exchanger element has an inlet and an outlet arranged at one end of the heat exchanger element. The heat exchanger device according to claim 12 and 13, characterized in that each of the heat exchanger elements has a substantially rectangular contour, the flow passage defined in each element comprises a passage section of meander-shaped flow extending substantially transverse at each end of the interconnected heat exchanger element by a longitudinally extending meander-shaped flow passage section. 15. The heat exchanger device according to any of claims 1-14, characterized in that it comprises a plurality of thermoelectric units which are divided into a variety of groups, the thermoelectric units of each group are electrically connected in series and the groups of thermoelectric units are mutually electrically connected in parallel. 16. The heat exchanger device according to any of claims 1-15, characterized in that the length of the flow passage adjacent to the hot side of the thermoelectric units is longer than that of the other flow passages adjacent to the cold side. of thermoelectric units. 17. The heat exchanger device according to any of claims 1-16, characterized in that the first and second heat exchanger elements are made of a heat conducting material, such as aluminum, copper and / or from alloys thereof. 18. The heat exchanger according to any of claims 1-17, characterized in that it is adapted to condition the air in the cab of a vehicle. 19. A system for conditioning the air in a space, such as the cabin of a vehicle, the system is characterized in that it comprises a heat exchanger device according to any of claims 1-18, the first and second passages of the device of Heat exchanger are included in first and second closed liquid circuits, respectively, each liquid circuit includes a radiator and means for circulating the liquid therethrough. 20. A system according to claim 19, for conditioning the air of a vehicle cabin, characterized in that the first liquid circuit includes part of the liquid cooling system of a combustion engine for driving the vehicle. SUMMARY OF THE INVENTION A heat exchanger device for an air conditioning system is described, especially for automobiles or other vehicles, comprising first and second heat exchanger elements (30, 31), which define first and second passages ( 32, 33), separated, for the medium that transports heat. Thermoelectric units (45) such as Peltier elements, are arranged between and have opposite heating and cooling surfaces in heat conduction contact with the first and second heat exchanger elements respectively. Each of the heat exchanger elements (30, 31) defines a passage (32, 33) of tortuous flow therein, having a length that is several times the maximum dimension of the heat exchanger element or a plurality of separate coextensive flow passages, each having a small cross-sectional area. Each flow passage (32, 33) is preferably a channel or slit formed in a side surface of the heat exchanger element (30, 31) and this side surface and the channels formed therein can be covered by a cover plate (43, 44). The thermoelectric units (45) can then be arranged between the cover plates (43, 44) of the first and second heat exchanger elements (30, 31).