Reliability of thermoelectric cooler
Refrigerating plate, reliability
1 Introduction:
As thermoelectric cooler is a solid based structure, it is generally believed that thermoelectric cooler has high reliability. In most application conditions, thermoelectric refrigeration devices can provide you with long-term trouble free service. At present, in many specific cases, the continuous working time of the thermoelectric cooler has exceeded 20 years, and the life of the thermoelectric cooler is longer than that of the relevant instruments. However, because the failure rate is closely related to the application environment, it is still difficult to obtain the reliability of specific thermoelectric refrigeration devices in practice. For some relatively stable refrigeration application conditions, the DC power supply loaded on the cooler is very stable and basically uninterrupted, at this time, the reliability of the thermoelectric cooler will be very high. The mean time between failures (MTBFs) generally exceeds 2000000 hours, and the MTBFs in this case are generally taken as the industrial standard. On the other hand, under the application conditions involving cold and hot cycle work, the mean time between failures will be greatly shortened, especially when the temperature of the thermoelectric cooler will rise to a higher temperature during the cycle.
Generally speaking, it is very difficult to publish the reliability data of thermoelectric coolers, because many application conditions and working parameters in practical applications will affect the final results. Therefore, reliability data is only valid for application environments similar to the test environment, and may not be applicable to other applications. Such factors as cooler installation and welding process, power supply and temperature control system and related technologies, temperature control, etc., combined with the external environment, will greatly affect the failure rate and make it fluctuate in a large range. In order to provide users with basic data about the life of thermoelectric refrigerators, and to help relevant engineers in the process of designing and optimizing the reliability of refrigerators, we designed several reliability tests of refrigerators to obtain the required reliability data. The test results and data under several application conditions are listed here, which can help the final consumers who use refrigerators under similar conditions. When providing users with these data, they should choose according to different application environments and user needs.
Some general requirements for the installation process of the thermoelectric cooler can be found in Part VI of this manual. In order to minimize the impact of incorrect installation process on the reliability of refrigerators, the installation process of all refrigerators must comply with the requirements mentioned in the manual. The main factors that affect the reliability of the cooler during installation are as follows:
a) The thermoelectric cooler has high mechanical strength under pressure, but its shear strength is relatively low. Therefore, it is generally not allowed to design the thermoelectric cooler in the mechanical structure system bearing the main support. In addition, under the application conditions that may involve vibration and shock, it is better to maintain proper pressure when installing the thermoelectric cooler, that is, use the screw clamping method. As for the hot spot cooler, as long as the proper installation method is used, it can successfully cope with the vibration or shock environment in aircraft, military or similar environments.
b) Although the maximum recommended pressure load for thermoelectric refrigerators is 15 kg per square centimeter (200 pounds per square inch), most refrigerators can withstand a pressure load of more than 15 kg per square centimeter (200 pounds per square inch) without failure during testing. The most important thing is to ensure that the installation method of the cooler is screw clamping and fixing, and the proper pressure is maintained during the installation process, so that the cooler will not be easy to loose under a small lateral force and cause movement. If several pairs of thermoelectric couples need to be fixed in the same refrigerator, loose parts will cause great trouble. In this case, if the pressure of the fixture is not enough during installation, the refrigeration performance may be reduced or even the refrigerator may fail in advance. If multi-stage cooler array installation is used, it is recommended to use a cooler with a height tolerance of ± 0.025 mm. In any case, the pressure of the fixture must be evenly applied and the surface must be flat (see Part VI for specific installation guidance).
