TEC Science Class：reveals how semiconductor coolers achieve "cooling" and "heating"!
1、 the working principle of semiconductor refrigerator- The Peltier effect
Semiconductor refrigeration is also known as thermoelectric refrigeration or thermoelectric refrigeration, and its working principle is based on the Peltier effect in the thermoelectric effect. The Paltier effect was born in 1834. A French physicist named Peltier found that when the current flows through the contact formed by two different conductors, the contact will produce heat transfer and heat absorption phenomenon, and the size of the heat transfer or heat absorption is determined by the size of the current. This is the phenomenon of cooling and heating of semiconductors, also known as the Paltier effect. Its heat is calculated by the formula Q=π*I.
2、the application of Paltier effect in semiconductor coolers
Let's take a look at the practical application of the Paltier effect in semiconductor coolers. As shown in the figure, a P-type semiconductor component and an N-type semiconductor component are connected into a thermocouple, and after connecting the DC power supply, the temperature difference and heat transfer will be generated at the junction. The charge carriers in the P element are holes, and the charge carriers in the N element are free electrons. At the upper junction, the current direction P→N, the temperature rises and the heat is released, which is the hot end; At the lower junction, the current direction N→P, the temperature drops and absorbs heat, which is the cold end.
▲ Peltier effect application model
Several pairs of semiconductor thermocouples are connected in series on the circuit to form a common thermoelectric refrigeration pile. After connecting the DC power supply, the thermopile above is the hot end, the following is the cold end, with the heat exchanger and other heat transfer means, so that the hot end of the thermopile heat dissipation and maintain a certain temperature, the cold end into the working environment to absorb heat and cool down, which realizes the Paltier effect in the semiconductor refrigerator application.
3、TEC cooling and heating mode temperature difference
After reading the above, we found the magic of the semiconductor refrigerator: it can achieve two effects of cooling and heating. The diagram shows the connection model of a semiconductor cooler and a peripheral device. Tc indicates the cold surface temperature on the side of the Object Being Cooled, that is, the target temperature; Th indicates the temperature on the hot surface of the Heat Sink, and Ta indicates the ambient temperature when the device works. ① TEC presents cooling mode when Tc < Ta, and Tc < Th; ② TEC presents heating mode when Tc > Ta, and Tc > Th
▲ Semiconductor cooler and peripheral device connection model(The figure is a schematic diagram of cooling, and the icon is reversed when heating)
4、 the basic structure of TEC cooling and heating mode
The basic structure of the semiconductor refrigerator in the two modes of cooling and heating also presents the opposite state. The diagram shows the structure of the cooling mode of the semiconductor refrigerator. The N-type DICE is connected to the positive electrode of the DC power supply (generally a red wire), and the P-type DICE is connected to the negative electrode of the power supply (generally a black wire), and the current begins to flow in the various semiconductor components. The upper joint electrodes begin to absorb heat, which is transmitted through DICE to the lower joint electrodes. The heat from this part of the movement and the heat from the input electricity will be released through the lower joint electrode.
▲ Semiconductor refrigerator refrigeration mode structure
It is assumed that the positive and negative poles connected to the DC power supply on the TEC exchange with each other, and the heat absorption and release relationship on and below the TEC will also change (positive and negative poles can also be selected to remain unchanged, and the internal PN flip), which forms the heating mode structure of the semiconductor refrigerator.
▲ Thermoelectric refrigerator heating mode structure
Next notice
In this TEC science class, we have learned the working principle and basic structure of semiconductor coolers, and the next period will continue to introduce its key parameters and performance, please look forward to it!
