Garrido Javier, Manzanares José A
Departament de Termodinàmica, Universitat de Valencia, 46100 Burjassot, Spain.
Materials (Basel). 2024 Sep 21;17(18):4640. doi: 10.3390/ma17184640.
The energy transported by the electric current that circulates a thermoelectric element (TE) varies with position due to the Joule and Thomson effects. The Thomson effect may enhance or compensate the Joule effect. A method for measuring the Thomson coefficient of a TE is presented. This method is based on the total compensation of the Joule and Thomson effects. The electric current then flows without delivering power to the TE or absorbing power from it. For a TE, the global Thomson/Joule compensation ratio Φ¯T/J is defined as the ratio of the power absorbed by the current due to the Thomson effect and the power delivered by the current to the TE due to the Joule effect. It can be expressed as Φ¯T/J=I0/I, where is the electric current and I0 is the zero-power current, a quantity that is proportional to the average Thomson coefficient. When I=I0, the Thomson effect exactly compensates the Joule effect and the net power delivered by the current to the TE is zero. Since the power delivered by the current is related to the temperature distribution, temperature measurements for currents around I0 can be used as the basis for a measurement technique of the Thomson coefficient. With varying current, the difference between the temperature at the center of the TE and the mean temperature between its extremes reverses its sign at the zero-power current, I=I0. This observation suggests the possibility of measuring the Thomson coefficient, but a quantitative analysis is needed. With calculations using the constant transport coefficients model for Bi2Te0.94Se0.063 and Bi0.25Sb0.752Te3, it is theoretically shown that a null temperature detector with a sensitivity of the order of 1 mK allows for the accurate determination of the Thomson coefficient.
流经热电元件（TE）的电流所传输的能量，由于焦耳效应和汤姆逊效应，会随位置而变化。汤姆逊效应可能增强或补偿焦耳效应。本文提出了一种测量热电元件汤姆逊系数的方法。该方法基于焦耳效应和汤姆逊效应的完全补偿。此时电流流动时既不向热电元件输送功率，也不从热电元件吸收功率。对于一个热电元件，全局汤姆逊/焦耳补偿比Φ¯T/J定义为电流因汤姆逊效应吸收的功率与电流因焦耳效应输送给热电元件的功率之比。它可以表示为Φ¯T/J = I0/I，其中I是电流，I0是零功率电流，该量与平均汤姆逊系数成正比。当I = I0时，汤姆逊效应恰好补偿焦耳效应，电流输送给热电元件的净功率为零。由于电流输送的功率与温度分布有关，对I0附近电流进行温度测量可作为汤姆逊系数测量技术的基础。随着电流变化，热电元件中心温度与两端平均温度之差在零功率电流I = I0处会改变符号。这一观察结果表明了测量汤姆逊系数的可能性，但还需要进行定量分析。通过使用Bi2Te0.94Se0.063和Bi0.25Sb0.752Te3的恒定传输系数模型进行计算，从理论上表明，灵敏度约为1 mK的零温度探测器能够准确测定汤姆逊系数。
