JPS63299383A - Thermoelectric converting module - Google Patents

Abstract

PURPOSE:To decrease the quantity of heat transferred from the heat generating face to the cooling face and to improve the thermoelectric converting efficiency, by providing a through hole at the center of each thermoelectric converting element for increasing the area of thermoelectric converting surface, and passing air or insulating fluid through the through hole. CONSTITUTION:Semiconductor thermoelectric converting elements 5 are composed of a Bi-Te thermoelectric material and integrated by means of copper plates 2 and 2'. The elements 5 are fixed by a ceramic plate. Each of the elements 5 has a through hole 6 of phi 2.5 mm at the center thereof. By passing cooling air through the through holes 6, it is possible to decrease heat loss within the elements and heat transfer loss from the heat generating face to the cooling face. Thereby, the thermoelectric converting efficiency can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a thermoelectric conversion module that performs thermoelectric cooling or thermoelectric power generation by utilizing the Peltier effect or the Seebeck effect.

2. Description of the Related Art A conventional thermoelectric conversion module of this type has a configuration as shown in FIG. 2, for example.

That is, the thermoelectric semiconductor element 1 is a solid solution of B, -7, system, and is a rectangular parallelepiped of several mm square.

This thermoelectric semiconductor element 1 has a P-type conductor plate 2 and an N-type conductor plate 2 made of Cu or the like.
two ceramic plates 3 which are electrically connected alternately by
3' in a grid pattern, and two power terminals 4, 4' were attached to the electrical connection ends.

Regarding the thermoelectric conversion module configured as above,
We will now explain the operation of thermoelectric cooling (for an explanation of the Peltier effect and Seebeck effect themselves, as well as a detailed explanation of the thermoelectric conversion module, see, for example, "Thermoelectric power generation using low heat drop" by Takenobu Kajiyo et al. (Explained in Research Institute Investigation Report No. 208 (Agency of Industrial Science and Technology) (1981), etc.).

When a DC voltage is applied between the two power terminals 4 and 4',
As electrons move between each electrically connected thermoelectric semiconductor element 1 and conductor plate 2, each electron absorbs and radiates thermal energy equivalent to the energy difference with respect to the electrons of both metals. As a result, the ceramic plate 3 on one side of the thermoelectric conversion module is endothermically cooled, and the heat is radiated through the ceramic plate 3' on the other side. Therefore, one side of the thermoelectric conversion module becomes a cooling surface and the other side becomes a heat generating surface, and heat transfer occurs from the cooling surface to the heat generating surface. At this time, it is well known that if the polarity of the DC voltage applied between the two power terminals 4 and 4' is reversed, the cooling surface and the heat generating surface can be reversed.

Conversely, by heating one side of the thermoelectric conversion module and cooling the other side to create a temperature difference, thermoelectric power generation occurs due to the so-called Seebeck effect, and DC power is generated between the power terminals 4 and 4'. .

Such thermoelectric conversion modules have fast temperature response,
Easy modularization, strong strength, easy maintenance, etc. 6
Although they have many advantages, they also have disadvantages such as high initial cost and poor operating efficiency, so their applications are currently limited. In particular, many reports have been made that if these shortcomings are resolved, it will be widely used in various fields including air conditioning and low heat drop power generation.

However, the current level of heat is generally beyond the scope of practical use.

In particular, factors that cause a decrease in efficiency during thermoelectric cooling will be explained with reference to FIG.

Using the Peltier coefficient α of the element pair, the temperature Th of the junction of the elements on the heat radiation side, and the current 1 to the thermoelectric conversion module, the heat absorption amount QP due to thermoelectric cooling (Peltier effect) is: QP = αITh ...・・・・・・
...(1), but if the loss of Joule heat due to current 1 flowing through the element is QJ, and the resistance value of the element is R, -12... 2) Q, -
jlR Furthermore, as the heat transfer loss QK that transfers heat from the heat radiation side to the heat absorption side, using the heat transfer coefficient determined by the material and structure of the element, Q - (Th - Tc) ......・・・・・・
...(In 31, it is expressed as -.

Figure 3 plots the equations (1) to (3) above, and the practically usable thermoelectric cooling capacity Q is Q = QP
-Q, -Q is one α+Th -! -12R-t (rh-To)・(4
), and it is clear that a current value of 1 indicates the local maximum value Qm. C0r is around 0.7 near this maximum value.

Here, if the resistance value R is lowered due to the physical structure (shape) in order to reduce QJ, there is a relationship in which the tooth becomes thicker, so it is not easy to expect an improvement in Q.

Although the explanation above has focused on thermoelectric cooling, similar results have been shown in thermoelectric power generation as well.

Problems to be Solved by the Invention As described above, the thermoelectric conversion module has the problem that Joule heat is transferred to the low-temperature image and that the heat transfer loss reduces the thermoelectric effect.

Means for Solving the Problems In order to solve the above problems, the thermoelectric conversion module of the present invention provides a through hole in the thermoelectric semiconductor element.

Function The thermoelectric conversion module of the present invention provides a through hole in the thermoelectric conversion element to increase the heat exchange area and allow air or an insulating fluid to pass therethrough, thereby releasing Joule heat generated inside the thermoelectric conversion element. By reducing the amount of heat transferred from the heat generating surface to the cooling surface, the efficiency of the thermoelectric conversion module is improved.

Now, explanation will be given using a simple element model as shown in FIG. In FIG. 4, (a) is a conventional thermoelectric conversion element, which has a structure with a cross-sectional area S1 and a length l, and is a semiconductor thermoelectric conversion element with uniform volume resistivity ρ and thermal conductivity. On the other hand, (b
) have the same physical properties, but there is a length of 0 at the center of the element.
．． 51. It is a semiconductor thermoelectric conversion element having a through hole with a cross-sectional area of 0.55, and if (aJ and (b) both have an upper surface of Th and a lower surface of Tc, the first
The heat loss is as shown in the table.

Table 1: Table 1 It is clear from this model that when considering semiconductor thermoelectric conversion elements with the same external shape, the Joule heat loss is 25% un s
It can be seen that the heat transfer loss is H, and the surface area from which heat is released is approximately 1.5 times larger.

That is, it can be seen that heat loss can be reduced by an increase in surface area and a decrease in heat transfer loss. Further, the increase in Joule heat can be reduced by making both side portions of the through hole thicker. At this time, heat transfer loss naturally increases, but since the surface area ratio remains unchanged, an improvement in efficiency is expected.

Example An embodiment of the present invention will be shown below.

FIG. 1 is a perspective view of an element of a thermoelectric conversion module according to the present invention, and in the figure, a semiconductor thermoelectric conversion element 5 is
-To-based thermoelectric material with a cross-sectional shape of 3 x 5
The length is approximately 8rnrn in mm. This semiconductor thermoelectric conversion element 5 is connected by an electrically connected copper plate 2.2'. Furthermore, these semiconductor thermoelectric conversion elements 5 are separated by ceramic plates (not shown). Each of the semiconductor thermoelectric conversion elements 5 has a capacity of 2.5 l.
A through hole 6 with a diameter of mm is provided in the center.

By ventilation cooling through the through holes 6 of this thermoelectric conversion module, heat loss generated inside the element and heat transfer loss from the heat generating surface to the cooling surface are reduced, and thermoelectric conversion efficiency can be improved.

In this embodiment, one circular through hole 6 is provided, but a plurality of through holes 6 may be provided in other shapes. Further, although air was sent to the through hole, cooling may be performed using insulating oil or the like.

Effects of the Invention As described above, in the present invention, by providing the thermoelectric conversion element C and the through hole, the thermoelectric conversion efficiency can be improved and the field of application of thermoelectric conversion can be expanded.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a thermoelectric conversion element according to a first embodiment of the present invention, FIG. 2 is a partial cross-sectional perspective view of a thermoelectric conversion element in a conventional example, and FIG. 3 is a thermoelectric conversion element 5...・Thermoelectric conversion element, 6...through hole. Name of agent: Patent attorney Toshio Nakao et al. 18th
■Figure 2

Claims (1)

[Claims] A thermoelectric conversion module in which a plurality of thermoelectric semiconductor elements are electrically connected to form a thermoelectric conversion module, and some or all of the thermoelectric semiconductor elements are each provided with at least one through hole in a direction perpendicular to heat flow.