Abstract
In recent years, thermoelectric (TE) devices have been used in several refrigeration applications and have gained attention for energy generation. To continue the development of devices with higher efficiency, it is necessary not only to characterize their materials but also to optimize device parameters (e.g., thermal contacts). One attempt to increase the efficiency at the device level consists of the replacement of the typical ceramic layers in TE modules by metallic plates, which have higher thermal conductivity. However, this alternative device design requires the use of a very thin electrical insulating layer between the metallic strips that connect the TE legs and the outer external layers, which introduces an additional thermal resistance. Impedance spectroscopy has been proved to be useful to achieve a detailed characterization of TE modules, being even capable to determine the internal thermal contact resistances of the device. For this reason, we use here the impedance method to analyze the device physics of these TE modules with outer metallic plates. We show for the first time that the impedance technique is able to quantify the thermal contact resistances between the metallic strips and the outer layers, which is very challenging for other techniques. Finally, we discuss from our analysis the prospects of using TE modules with external metallic plates.
Highlights
Thermoelectric (TE) materials have the ability to convert heat into electricity or use electricity to create a temperature difference
We show for the first time how impedance spectroscopy can characterize these thermal contacts, which is very difficult to achieve by other techniques
We showed how impedance spectroscopy is capable of quantifying these thermal contact resistances, which are usually negligible in TE modules with the typical ceramic layers, by measuring two modules with outer metallic layers
Summary
Thermoelectric (TE) materials have the ability to convert heat into electricity or use electricity to create a temperature difference. Article we have shown how to characterize the thermal contact resistance between the TE legs and the metallic strips.[18] In the latter study, we developed the most comprehensive equivalent circuit to date, which includes, among other key phenomena, the thermal contact resistance between the metallic strips and the outer layer This parameter is essential to evaluate the effect of the thin insulating layers in modules with external metallic layers. The fitting of experimental data to an impedance equivalent circuit is the most common way adopted to extract the parameters of interest from the system under study These alternatively designed modules use a thin epoxy layer between the metallic strips and the outer metallic layers to avoid the electrical contact, which introduces thermal contact resistances. Are directly obtained, which is very challenging for other techniques
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