The Elusive Thomson Effect in Thermoelectric Devices. Experimental Investigation from 363 K to 213 K on Various Peltier Modules

Abstract

At steady state, in the governing equation of one-stage thermoelectric cooler, the heat resulting from Fourier conduction is balanced by heat generation due to the Joule and Thomson effects inside semiconductors. Since the heat flux observed at the junction of a semiconductor, r pair includes the Peltier effect and the Fourier heat flux caused by both the aforementioned contributions, the Thomson effect is easily masked by the Joule heat, which makes it elusive. With the aim of highlighting the contribution of the Thomson effect, measurements were carried out in the temperature range from 363 K to 213 K on different Peltier modules. The temperature dependence of the Seebeck and Thomson coefficients was evaluated as well as the electrical resistivity, and thermal conductivity of the Peltier modules examined. The results obtained show that the temperature dependence of the thermoelectric properties can reduce the cooling capacity of the Peltier module compared to what is declared in the technical datasheets of the commercial devices. The analyses allow us to conclude that an increase in the Thomson effect could have a positive effect on the performance of the Peltier only if it were possible to reduce the Joule contribution simultaneously.

Experimental characterization of a commercial TEG device under mimicked operating conditions

“…The properties of the thermoelectric material were determined, as a function of temperature, by performing measurements in a thermostatic chamber at temperatures ranging from 10 °C to 180 °C. The apparatus and measurement methodology are those that have already been described in a previous work [23]; the arrangement and procedure detailed therein were adopted.…”

“…Three similar TEG modules, which were powered in sequence with electric current I imposed by the DX 4090 instrument (typically in the 20-50 mA range) at each measurement temperature, were studied. The total Seebeck voltage DV S produced at the junctions was measured as reported in [23]. A supply current of 25 mA was applied in all the tests to make the Joule effect negligible, according to the Harman method [24].…”

Thermal Imaging of the Thomson Effect

“…The Thomson effect also plays a role in thermoelectric behavior. Often, however, it goes ignored because it is difficult to measure, and, in practice, manifests as a small correction to the analysis of thermoelectric devices [3].…”

“…For nearly 100 years, scientists have been attempting to directly measure the Thomson effect and its influence on other thermophysical phenomena. But until now, the effect had only been detected indirectly by either comparing Joule heating in a material to heating or cooling due to the Thomson effect as the charge current across the material was decreased [5] or by observing the temperature dependence of the Seebeck coefficient [3]. The new results from Uchida and his colleagues solve that deficiency, providing the first direct measurements of the effect.…”

“…The enhancement of the Thomson coefficient when a magnetic field is applied indicates a potential improvement of the cooling efficiency of the material. This behavior could be used to create magnetic cooling devices in which the Thomson effect compensates for Joule heating [3].…”