How to carry out multi-stage refrigeration for semiconductor refrigerator

In principle, the semiconductor cooler is a heat transfer tool. When current flows through a thermocouple pair composed of a piece of N-type semiconductor material and a piece of P-type semiconductor material, heat will be transferred between the two ends, and heat will be transferred from one end to the other, resulting in temperature difference to form a cold and hot end. However, semiconductors themselves have resistance. When the current passes through the semiconductor, it will generate heat, which will affect the heat transfer. Moreover, the heat between the two plates will be transferred reversely through the air and the semiconductor material itself. When the cold end and the hot end reach a certain temperature difference and the two kinds of heat transfer are equal, a balance point will be reached, and the positive and negative heat transfer will cancel each other out. At this time, the temperature of the hot and cold ends will not continue to change. In order to achieve a lower temperature, we can reduce the temperature of the hot end by radiating heat.

The function of the fan and radiator is mainly to dissipate heat for the hot end of the heat sink. Usually, the temperature difference between the cold end and the hot end of the semiconductor refrigeration chip can reach 40 ~ 65 degrees. If the temperature of the hot end is reduced by active heat dissipation, the temperature of the cold end will also be reduced accordingly, thus reaching a lower temperature.

When a piece of N-type semiconductor material and a piece of P-type semiconductor material are connected to form an electric couple, after DC current is connected in this circuit, energy can be transferred, and the current flows from the N-type element to the junction of the P-type element to absorb heat and become a cold end; The junction from P-type element to N-type element releases heat and becomes hot end. The magnitude of heat absorption and heat release is determined by the magnitude of current and the number of elements of semiconductor materials N and P. The following three points are thermoelectric effects of thermoelectric refrigeration.