Principle of semiconductor refrigeration

Semiconductor refrigeration, also known as thermoelectric refrigeration, is a discipline developed from the 1950s on the edge of refrigeration technology and semiconductor technology. It uses a P-N junction composed of special semiconductor materials to form a thermocouple pair and produce a Peltier effect.

 

1. Principles of Semiconductor Refrigeration - Introduction

 

A semiconductor chiller is a cooling device composed of a semiconductor, also called thermoelectric refrigeration. Its theoretical basis is the Peltier effect. After the power is applied, the heat at the cold end is moved to the hot end, and the temperature at the cold junction is lowered. The temperature rises. As shown, a closed circuit consisting of two different metal wires, X and Y.

 

Compared with the traditional refrigeration technology, its advantages are: (1) simple structure, no noise, no wear, no pollution, high reliability; (2) fast cooling speed, flexible control; (3) thermopile can be arbitrarily arranged Cloth, size and shape are variable. Due to the above advantages, this technology is being vigorously promoted at home and abroad.

 

From the development history of semiconductor refrigeration, it has experienced three stages: 1. At the beginning of this century, Seker and Peltier discovered the phenomenon of temperature difference current and temperature anomaly, and carried out research on thermoelectric power generation and thermoelectric refrigeration. However, due to the poor thermoelectric properties of the metal materials used, the efficiency of energy conversion was very low, and the thermoelectric effect was not practically applied. In the early 2nd century, it was found that semiconductor materials have good thermoelectric properties through extensive application of semiconductor materials. The efficiency of the thermoelectric effect is greatly improved, so that thermoelectric power generation and thermoelectric refrigeration enter engineering practice. After the 1980s, the efforts were made to improve the performance of semiconductor thermoelectric refrigeration and further develop the application field of thermoelectric refrigeration.

 

2. Semiconductor refrigeration principle - typical structure

 

The following figure is a typical structure of a refrigerator. The particles of many N-type and P-type semiconductors are arranged one on another, and the NPs are connected by a common conductor to form a complete line, usually copper, aluminum or other metal conductors. Finally, the two ceramic pieces are sandwiched like a sandwich biscuit. The ceramic piece must be insulated and have good thermal conductivity and look like a sandwich.

 

3. Semiconductor refrigeration principle - working principle

 

The working principle of semiconductor refrigeration is based on the Peltier effect. As shown in the following figure, a semiconductor thermocouple is composed of an N-type semiconductor and a P-type semiconductor. N-type semiconductors have extra electrons and have a negative temperature difference potential. P-type semiconductor electrons are insufficient, and there is a positive temperature difference potential; when electrons pass from the P-type to the N-type, the temperature of the node decreases, the energy thereof increases, and the added energy is equivalent to the energy consumed by the node. Conversely, when electrons flow from the N-type to the P-type material, the temperature of the junction increases.

 

The direct contact thermocouple circuit is not available in practical applications, so the connection method of the following figure is used instead. Experiments have shown that the introduction of a third material (copper connection piece and wire) in the temperature difference circuit does not change the characteristics of the circuit. In this way, the semiconductor component can be used to meet the requirements of the user by various connection methods. A P-type semiconductor component and an N-type semiconductor component are coupled into a pair of thermocouples, and after the DC power supply is connected, a temperature difference is generated at the joint. And the transfer of heat.