Thermoelectric cooling system

Abstract: An ecological thermoelectric cooling system composed of a thermoelectric plate by the coupling to the same of a metal supplement on its cold generating face (1) and two dissipators, one on the free face of the metal supplement, and the other, refrigerated by natural or forced convection, on the heat generating face (2). To avoid the formation of a thermal bridge between the two faces and to increase mechanical rigidity a part made of insulating material is mounted joined to the two dissipators by rods arranged in a non - coaxial form.

Description: The invention relates to a thermoelectric cooling module, based on the usage of commercially available semiconductor elements. For the purposes of this, a heat transmission system has had to be developed which optimizes the power generated, attaining levels of performance unknown to date in the field of gas - free cooling (ecological refrigeration). There are some patents which are related to this field: Patent US-A-3137141 refers to a thermoelectric water cooler comprising a supporting wall with a plurality of transverse openings therethrough, a cooling member including a first water coil cast within a block of metal with one end connected to a source of water and having its other end adapted to be connected to an outlet for dispensing cooled water, a heat dissipating element including a water coil cast within a second block of metal and having one end adapted to be connected to a source of water and having its other end adapted to be connected to an outlet for the water heated by the passage therethrough, and a thermoelectric module between them. The two dissipating elements are arranged to the thermoelectric module in a manner that it is not possible to avoid the thermal bridge between them. Patent US-A-3450572 refers to a thermoelectric battery which is clamped between two heat exchangers having beyond the clamping area, two opposite faces with a layer of thermally insulating material sandwiched between them. The arrangement proposed by this patent is not the best to obtain the optimum mechanical rigidity and an adequate thermal insulation between the two faces in order to avoid the thermal bridge. The cooling system according to claim 1 comprises a thermoelectric plate of a type that is commercially available, to which a metal block is added, preferentially manufactured of aluminium, on the side which is to be used to generate cold; together with two dissipators, one on the heat emitting side and the other on the free side of the metal supplement. The perfection of the contact between the surfaces in question (plate and supplement; plate - dissipator 1; free side of metal supplement - dissipator 2) is extremely important. For this purpose, the use of some highly conductive substance is advisable to ensure the quality of the contact (such as high conductivity silicon or copper sulphate) thereby avoiding the appearance of harmful thermal resistances. Another critical point of the system is the design of the dissipators and especially of the heat emitting side. The one used in cur module is of our own design, on the basis of a commercially available dissipator. The modifications made to this have the aim of reducing, as far as is possible, thermal resistance (dissipator - atmosphere) for forced convection working. To this end it has been machined, reducing its base to 4 mm and the width of its fins to 2 mm, while also leaving the latter completely straight. As a result of this, we obtain a thermal resistance of 0.05 ° C/W, working with an axial fan which blows the air frontally onto the dissipator. The air, as has already been mentioned, must be blown frontally with the aim of achieving maximum turbulence, using commercially available low profile fans. Some type of holding is needed to attain the mechanical rigidity of the module. This must be achieved without giving rise to any form of thermal bridge between the cooling side and that which emits heat. Account must be taken of the fact that if this anomaly does occur (for example, through the usage of metal bolts and nuts) then the resulting losses are of a high magnitude (approximately 32 %). It is for this reason that, an intermediate plate of insulating material through which metal rods are bolted, from each dissipator in alternate fashion must be used. As an example of the application of the system, a prototype has been developed, as is shown in figure 1, which consists cf a tank of liquid (water, for example) to which on opposing sides six modules in two groups of three have been affixed, leaving the dissipators (1) with refrigerating sides (2) within the tank. A metal block (8) is located between the dissipator (3) and the refrigerating side (2) of the thermoelectric plate. The dissipators (3) with heat emitting sides (4) remain on the outside, working in forced convection mode with the aid of low profile axial fans (5). Two such fans are used fcr each group of three modules, as was mentioned above, while the airflow is directed in front of the fans by means of small nozzles. The mechanical rigidity of each module is achieved through the joining of the two dissipators in the method shown in figure 2. In this figure the part made of insulating material (6) may be seen, together with the metal rods (7) that are embedded in the said part without touching one another, avoiding thermal bridges. The supply of electricity to the modules is ensured by using a commercially available direct current power source. In the definitive model, it will be possible to include a power source manufactured in - house within the system as a whole. In the prototype the modules are equipped with 60 W plates, attaining the following temperatures at an ambient temperature of 30° C: Temperature on the cold side = - 10° C Temperature on the hot side = 33° C Water temperature = - 2° C If the cooling coil of a drink dispenser (such as one for beer or soft drinks) is placed within this equipment, then the liquid is cooled to a suitable degree. Amongst the advantages of the system, the following points may be listed: Cooling without using refrigerating gas. The absence of moving parts (except for the fans). High performance. Low voltage power supply. The simplicity of the system, given that it is very compact. Flexibility and ease cf adaptation.

Claims: A thermoelectric cooling system comprising an intermediate plate (6) made of heat insulating material, a thermoelectric cooling module arranged in an opening of the plate (6) together with a metal block (8) coupled to the cold side (2), in use, of the module, a heat dissipator (3) clamped to the intermediate plate (6) of the module and a cold dissipator (1) clamped to the intermediate plate (6), characterized in that it includes first connecting rods (7) threaded or embedded in the plate for clamping the cold dissipator to the intermediate plate (6) and second connecting rods (9) threaded or embedded in the plate for clamping the heat dissipator (3) to the intermediate plate (6), said first connecting rods (7) are offset from the second connecting rods (9) so as to be out of alignement therewith to increase the mechanical rigidity and the thermal insulation of the system. A thermoelectric cooling system according to the above claim, characterized in that the heat dissipator (3) has fins. A thermoelectric cooling system according to claim 1, characterized in that the heat dissipator (8) consists of the wall of the recipient or enclosured to be cooled. A thermoelectric cooling system according to claim 1, characterized in that the heat dissipator (1) incorporates a finned heat exchanger working in forced convection with the aid of fans (5). A thermoelectric cooling system according to the above claim, characterized in that it includes switching means to permit the alternate cooling and heating of any type of material, solid, liquid or gas.

Inventors: ACOSTA MALIA FRANCISCO JAVIER, ACOSTA MALIA LUIS SALVADOR, ACOSTA MALIA, FRANCISCO JAVIER, ACOSTA MALIA, LUIS SALVADOR
Applicants: ACOSTA MALIA FRANCISCO JAVIER, ACOSTA MALIA LUIS SALVADOR, ACOSTA MALIA, FRANCISCO JAVIER, ACOSTA MALIA, LUIS SALVADOR
Application year: 1995
Main classification: F25B21
IPC codes: H01L35, F25B21