Unsteady State of a Solid State Device: Characteristic Cooling Length

Thermoelectric modules (TEM) are solid state devices that can work as a Thermoelectric cooler (TEC). TECs can reach temperatures below that obtained with a steady-state current by applying an electrical current pulse which enables a transitory state in a Peltier couple. This phenomenon is known as supercooling. The objective of this work is to analyze characteristics parameters such as minimum cooling temperature, COP and temperature spatial profile in a TEC operated under current pulses and cooling load (Qc) pulses. We study a numerical model of a one-dimensional thermoelectric cooling system in the unsteady state. In this work, we propose a new parameter called characteristic cooling length to describe the distance in which occurs minimum cooling temperature in the elements of a TEM. Our results show the transient temperature spatial profile along the thermoelements of the TEM and the characteristic cooling length for different materials. We propose a general principle to make a judgment how the temperature profile will occur along the elements due to material properties under current pulse operation.