WO1996012920A1

WO1996012920A1 - Ecological thermoelectric refrigerating system

Info

Publication number: WO1996012920A1
Application number: PCT/ES1995/000099
Authority: WO
Inventors: Luis Salvador Acosta Malia; Francisco Javier Acosta Malia
Original assignee: Luis Salvador Acosta Malia; Francisco Javier Acosta Malia
Priority date: 1994-10-20
Filing date: 1995-08-09
Publication date: 1996-05-02
Also published as: MX9602404A; ZA958912B; CN1137312A; JPH09507566A; MA23696A1; DE69500158D1; ATE148940T1; CA2179431A1; EP0719993A1; EP0719993B1; IL115686A0; AU3167395A

Abstract

Ecological thermoelectric refrigerating system comprised of a thermoelectric plate by coupling to the latter a supplementary metal plate on the cold generating face (1) and two dissipators, one dissipator being arranged on the supplementary metal element and the other dissipator being refrigerated by natural or forced convection to the heat generating face (2). In order to avoid the thermal bridge between both faces and in order to provide mechanical rigidity to the assembly an isolating material is mounted between the two dissipators.

Description

DESCRIPTION

ECOLOGICAL THERMOELECTRIC REFRIGERATOR SYSTEM

The system developed consists of the integration of a totally ecological refrigeration module, based on the use of semiconductor elements existing in the market.To do this, it has been necessary to develop a heat transmission system that optimizes the power generated, achieving yields so far unknown in the field of cold without gases (Ecological cold).

The module consists of a Thermoelectric plate, of those existing in the market, to which we place a metallic supplement, preferably of aluminum, on the face that we will use as a cold generator; and two heatsinks, one on the heat generating face and the other on the free car of the metallic supplement.

It is very important the perfection achieved in the contact of the surfaces in play (plate-supplement; plate-dissipator 1; free face of the supplement-dissipator 2). Pair. It is convenient to use some highly conductive substance that ensures contact quality (for example, high conductivity silicone or Copper sulfate), thus avoiding the appearance of harmful thermal resistance.

Another critical point of the system is the design of the heatsinks and, in particular, that of the heat generating face. The one used in our module is our own, having started from a commercial heatsink. I modified them. carried out therein have focused on reducing, as far as possible, the thermal resistance (heatsink-environment) for operation in forced convection. For This was subjected to mechanization, reducing its base to 4 mm and the width of its fins to 2 mm, leaving them completely straight. As a result, we obtain a heatsink with a thermal resistance of 0.05 "C / w, operating with an axial fan that drives the air in the front direction towards the heatsink. The air flow, as we have said, must be in the frontal direction with in order to achieve maximum turbulence, using low profile commercial fans.

Some type of support is necessary to achieve the mechanical rigidity of the module. This must be achieved without causing any thermal bridge between the cold and heat generating face. Bear in mind that if this anomaly occurs (for example by means of metal screws) the losses that take place are of great magnitude (approximately 32%) .To do this, it is necessary to use thermally insulating material screws or an intermediate plate of insulating material to which are bolted metal studs coming from each heatsink df alternative way.The second solution is the one we use.

As an example of the application of the system, a prototype has been developed, which is represented in figure 1, which consisted of a liquid tank (for example, water) to which six modules in two groups of units have been attached on opposite sides. three, leaving the heatsinks of the cold-generating faces (l) inside the tank. The heatsinks of the heat-generating faces (2), remain outside, operating in forced convection with the help of axial profile fans low (3). Two of these fans are used for each group of three modules, mentioned above, the air flow being directed in the front direction to the fans by means of small nozzles. The mechanical rigidity of each module is achieved by joining the two heatsinks as shown in Figure 2. It shows the piece of insulating material (1) and the metal studs (2), embedded in said piece and without entering in contact, avoiding thermal bridges.

The power supply to the modules is carried out by means of a DC power supply of those existing in the market. In the final model, a source d 'own manufactured power supply could be integrated into the set.

In the prototype the modules are equipped with 60w plates, achieving, with an environment of 30 ^to C, the following temperatures:

Cold face temperature = -10 "C Hot face temperature» 33 * C Water temperature = - 2 * C

By introducing into this equipment a coil of a beverage dispenser (for example, beers or soft drinks), adequate cooling of the liquid is achieved.

Among the advantages of the system can be listed:

- Refrigeration without using refrigerant gas.

- Absence of moving elements (fans only)

- High performance. - Low voltage power.

- Simplicity of the system, since it is very compact.

- Flexibility, adapts easily.

Claims

The ownership and exclusive exploitation of:

1) .- ECOLOGICAL THERMOELECTRIC REFRIGERATOR SYSTEM, characterized by the use of the cold generated by a thermoelectric plate by means of the coupling of a metallic supplement on the cold generating face and of special design heatsinks, one on the free face of metallic supplement and, the other, on the heat generating face, cooled by natural or forced convection.

2) .- A system according to claim 1, characterized in that the thermal insulation of the two faces and, therefore, the optimization of the system, is achieved by the different fastening of the two heatsinks with the intermediation of an insulating material, achieving, in this way the rupture of the thermal bridge between both faces and, at the same time, the mechanical rigidity.

3) A system according to claims 1 and 2, which mounted on different faces of a liquid tank, can be used in cooling a coil of a liquid dispenser.

4) .- A system according to claims 1 and later, which can be used for cooling or heating any material (solids, liquids or gases).

MODIFIED CLAIMS

[received by the International Bureau on January 25, 1996 (25.01.96); claims 1 -4 replaced by modified claims 1-5 (1 page)

1 .- refrigerator system ecological thermoelectric, of those who use the cold generated by a thermoelectric plate by a coupling to the same of a metal supplement in generating face cold and two dissipators, respectively, on the free side of this supplement metallic and on the heat generating face, of those cooled either by natural or forced convection, essentially characterized by increasing both the mechanical stiffness and the thermal insulation of the two faces and the rupture of the thermal bridge, by means of the different clamping of the two heatsinks, in non-coaxial arrangement of its tightening means.

2 .- refrigerator system ecological thermoelectric according to the preceding claim, characterized in that the overall mechanical rigidity is ensured by the clamping means or studs (2) are incorporated threaded or alternatively, embedded in the plate or intermediate piece (1) , of thermal insulating material, surrounding the pair constituted by the metallic supplement and the thermoelectric plate, studs (2) that are arranged alternately, that is to say, off-center those that tighten the heat sink with respect to those that squeeze the heat sink cold.

3 .- ecological thermoelectric cooling system, according to previous claims, characterized in that the cold sink may have fins or be, simply, the wall of the container or enclosure to be cooled.

4 .- ecological thermoelectric cooling system, according to claim 1 and 2, wherein the heat sink includes a heat exchanger finned operating in forced convection with the aid of fans.

5 .- ecological thermoelectric cooling system, according to previous claims, characterized by alternately enable cooling or heating of any type of material, solid, liquid or gaseous. Statement πnder Art 19 (1) of the PCT (Rule 46.4 of the PCT Regnlations)

Claim 1 has been amended by separating the background of the invention, specifically the elements composing the theπnoelectric module, from the elements that characteríze the invention, i.e. the holding system, its arrangement and the constructional form itself of the theπnoelectric module.

Claim 1 is described on page 2, lines 11 to 22 and on page 3, Unes 1 to 5, and illustrated in Hgure 2, followed by drawings of the example with different sections of the same object, which were merely intended for a better co prehension of the claim. Likewise, Figure 2 was drawn following a common practice in technical and patent documents. It is not a real section but a projective section of the frame or píate (1) on which the studs (2) are projected, to give an overall idea of the holder system therein claimed.

Figures 2c and 2d hereto attached, however, are real AA 'and BB' sections of 2a, where heat (6) and cold (7) dispersers have been included to complete the unit (refer to Description, page 3, lines 1 - 3 ).

As can be seen in the figures, this holder system is characterized by the incorporation of a frame, piate or intermediaíate piece (1) of thermal insulating material (see Description, page 2, lines 18 - 19), situated adjacent to or surrounding ( see Figure 2a hereto attached) a metallic supplement (4) and a thermoelectric píate (5) (see Description, page 1, lines 11-14). To this insulating frame, threaded studs (2) are screwed (Description, page. 2, line 19) or embedded (Description, page 3, lines 3 - 5) in an altérnate manner (Descríption, page 2, lines 20 - 21) , a con g guration which can be clearly observed in Figures 2a and 2b hereto attached.

Said altérnate arrangement means that the studs that hold the heat disperser to the unit are offcentered (on different axes) with respect to those holding the cold disperser, thus general mechanical stiffness being assured through the frame or píate (1) as claimed. This point was mentioned in the Description and Figures, but probably not explained clearly enough.

The dispersers may be provided with fíns or simply be the wall of the vessel or cooling area. Equally, the heat disperser (6) may be a finned heat exchanger working in fan-aided forced convection (Description, page 2, lines 29-32). The studs (2), because of not being set coaxial but alternately, can be embedded into the insulating frame, concretely in a hole (8) finished to size so that the stud will not turn, as can be seen in Figures 2c and 2d . In this way, the gripping is assured by the nut (9) screwed onto the disperser.

The improvement achieved in the contacts or joints between cold disperser (7) - metallic supplement (4) - theπnoelectric píate (5) - heat disperser (6) elements is decisive in obtaining a better transmission of the heat pumped by the thermoelectric píate (Description , page 1, lines 18-20). Henee the convenience of using a highly conductive substance to assure the contact quality (Description, page 1, lins 20-25).

Likewise, it is necessary that the holder system assures a high mechanical stiffness without causing thermal bridges between the faces of cold and heat dispersers (Description, page 2, lines 11 - 14).

The proposed holder system was engineered in order to satisfy these needs and allow application of high levéis of gripping to the module unit, cióse to the stud's (2) resistance, meaning high pressures of contact between the joints (Figure 2) of the elements.

According to theoretical calculations (Rohsenow & Hartnet, Handbook of Heat Transfer, 1973), the thermal resistance of contact depends on said pressure to a considerable extent, which demonstrates the great importance of achieving an adequate level of gripping.

As mentioned in the Description, page, 2, lines 14 - 17, losses in a thermoelectric module derived from the use of four studs of 5-mm diameter to hold the unit, without any device to break the thermal bridge between the cold and hot faces, are quite signifϊcant (about 32%).

Thanks to the non-coaxial, ie altérnate, arrangement, the holder system proposed in patent application No. ES / 95/00099 notably reduces these losses and, evidently, all the more when the mass of the collated insulant, whether by means of screwed or embedded studs, is greater. This new configuration offers the possibility of using a great amount of insulating material between the studs (2), thus considerably reducing the losses while maintaining an optimum thickness of the metallic supplement (4) (Description, page 1, lines 11 -1 6) . This would be impossible to achieve with a coaxial configuration because it would be necessary to separate, unnecessarily, the heat (6) and cold (7) dispersers by means of a bigger metallic supplement (4), subsequently increasing the distance between the studs in order to introduce necessary mass of insulant. This would produce a negative effect due to introducing supplementary thermal resistances which would offset the possible benefits attainable.