Refrigeration – Using electrical or magnetic effect – Thermoelectric; e.g. – peltier effect
Reexamination Certificate
2001-11-20
2002-11-05
Jiang, Chew-Wen (Department: 3744)
Refrigeration
Using electrical or magnetic effect
Thermoelectric; e.g., peltier effect
C062S003200
Reexamination Certificate
active
06474073
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to. a thermoelectric device utilizing, a thermoelectric module utilizable in a refrigerating apparatus and, more particularly to a thermoelectric manifold capable of cooling or heating a thermal medium in a fluid circuit for the thermal medium by utilization of a thermoelectric effect.
BACKGROUND ART
In recent years, depletion of the ozone layer in contact with fluorinated hydrocarbon gas has come to be a global problem and immediate development of refrigerating apparatuses that do not use fluorinated hydrocarbons is desired. Also, with the standard refrigerating apparatus utilizing a compressor, noises generated from the compressor are offensive to the ears particularly where the environment in which it is used is quiet. As one of the refrigerating apparatuses that do not use fluorinated hydrocarbons the refrigerating apparatus utilizing a thermoelectric module has now come to be spotlighted.
The Peltier effect is generally well known as a phenomenon in which when a weak electric current flows across the interface between dissimilar metals heat is evolved and absorbed. The thermoelectric module utilizing this Peltier effect is of a design in which pluralities of P-type semiconductor elements and N-type semiconductor elements are arranged in a matrix pattern, having been connected in series with each other through electrodes and are sandwiched between heat transfer plates to render the resultant assembly to represent a generally flat configuration. In this thermoelectric module, when a direct current is applied in one direction to the semiconductor elements, the heat transfer plates are cooled and heated, respectively, by the Peltier effect. Accordingly, one of the heat transfer surfaces acts as an exothermic surface whereas the other of the heat transfer surfaces acts as an endothermic surface.
In the thermoelectric module, it is thought that heat is transported from the endothermic surface towards the exothermic surface by the effect of exchange of kinetic energies and heat energies of electrons flowing through the semiconductor elements. Accordingly, if it is assumed that no heat conduction take place between the heat transfer plates through the semiconductor elements, the difference in temperature between-the endothermic and exothermic surfaces of the single thermoelectric module can be increased by choosing the number of the semiconductor elements and the electric current density.
In reality, however, heat evolved in the heat transfer plate on a heating side transfers to the heat transfer plate on a cooling side as a result of a heat conduction through the semiconductor elements. Accordingly, if the temperature difference between the endothermic and exothermic surfaces of the single thermoelectric module becomes large, the heat capacity brought about upon cooling or heating by the Peltier effect and the heat capacity of the above described heat conduction are counterbalanced with each other and no continued application of an electric current would result in increase of the temperature difference.
Accordingly, in order. for the thermoelectric device having the thermoelectric module built therein to enable the endothermic surface to be cooled down to a desired temperature, the Japanese Laid-open Patent Publication No. 8-236820 discloses stacking of a plurality of thermoelectric module one above the other so that they can be cooled stepwise to thereby enable the endothermic surface on a cooling side to be cooled down to a desired temperature.
With the prior art thermoelectric module, since the pluralities of the P-type semiconductor elements and N-type semiconductor elements are arranged in a matrix pattern and heat transport takes place in each of the semiconductor elements by the Peltier effect, a center portion of the endothermic surface is lower in temperature than that at a peripheral edge portion thereof and, on the other hand, a center portion of the exothermic surface is higher in temperature than that at a peripheral edge portion thereof. If a gradient occurs in a pattern of distribution of temperature at the endothermic surface and also at the exothermic surface, the cooling efficiency exhibited by the endothermic surface as a whole tends to be lowered. In particular, in the thermoelectric refrigerating apparatus utilizing the multi-staged thermoelectric modules, the temperature gradient tends to become large.
Once the temperature gradient becomes large, not only is the heat exchange efficiency reduced, but the thermoelectric module is susceptible to bowing deformation. In such case, cracking may occur at the joint between the semiconductor elements and the electrodes. Also, where a pair of heat transfer plate are used for each of the thermoelectric modules and the heat transfer plates are joined together to allow the plural thermoelectric modules to be laminated, bowing of one or more thermoelectric modules will result in separation of the heat transfer plates from each other and no heat transmission would occur properly between the thermoelectric module.
DISCLOSURE OF THE INVENTION
The present invention has for its object to provide a thermoelectric device such as a thermoelectric manifold having a multi-stage of thermoelectric modules, wherein the heat exchange efficiency is increased by equalizing heat distribution in each of the endothermic and exothermic surfaces and thermal strains in the thermoelectric modules are suppressed so that even though bowing takes place the heat transmission can favorably take place between the thermoelectric modules.
In order to accomplish the above described object, the present invention is such that in the thermoelectric device provided with a plurality of thermoelectric modules, a fluid that serves as a heat transfer medium is intervened between the thermoelectric modules so that through this fluid heat transmission takes place from an exothermic surface of the thermoelectric module on a cooling side towards an endothermic surface of the thermoelectric module on a heating side. Thus, if the heat transmission is caused to occur indirectly between the thermoelectric modules through the fluid, even when thermal strains are induced in the thermoelectric modules, the heat transfer medium favorably contacts the endothermic and exothermic surfaces of the thermoelectric modules with the heat transmission taking place favorably between the thermoelectric modules. Also, heat distribution at the endothermic or exothermic surface of each of the thermoelectric modules held in contact with the fluid can be equalized to thereby increase the heat exchange efficiency and also to lessen the thermal stresses in the thermoelectric modules.
The thermoelectric device of the present invention includes a plurality of thermoelectric modules each having endothermic and exothermic surfaces, wherein when an electric current is supplied the exothermic surface is heated and the endothermic surface is cooled, the plural thermoelectric modules being juxtaposed to each other with the exothermic surface of one of the neighboring thermoelectric modules and the endothermic surface of the other of the neighboring thermoelectric modules being held in face-to-face relation with each other; and a cavity defining member for defining a heat transfer cavity between the neighboring thermoelectric modules.
In the present invention, the fluid that serves as the heat transfer medium is sealed within, or is allowed to flow through, the heat transfer cavity and, by so doing, heat transfer takes place from the exothermic surface of one of the neighboring thermoelectric modules to the endothermic surface of the other of the neighboring thermoelectric modules through this fluid. Accordingly, even-when one or some of the thermoelectric module is deformed to bow under the influence of the thermal strains, the heat transfer medium favorably contacts the exothermic and endothermic surfaces and the heat transfer from the exothermic surface of the thermoelectric module on the cooling side towards the endothermic surface of the the
Fujimoto Masatsugu
Inamori Syouhei
Kido Osao
Morishita Kenichi
Uetsuji Toshio
Jiang Chew-Wen
Matsushita Refrigeration Company
Wenderoth , Lind & Ponack, L.L.P.
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