How to solve the problem of high compressor pressure

The main reasons of compressor exhaust temperature overheating are: high return air temperature, high heat generation of motor, high compression ratio, high condensation pressure and improper selection of refrigerant. 1. The high return air temperature is related to the evaporation temperature. In order to prevent the liquid from flowing back, the return air superheat is generally required to be 20℃ in the return air pipeline. If the return air duct is not well insulated, the superheat will far exceed 20℃. The higher the return air temperature, the higher the intake temperature and exhaust temperature of the cylinder. When the return air temperature increases by 65438 0℃, the exhaust air temperature will increase by 65438 0 ~ 65438 0.3℃. 2. Motor heating For the return air cooling compressor, the refrigerant vapor is heated by the motor when it flows through the motor cavity, and the suction temperature of the cylinder rises again. The calorific value of motor is influenced by power and efficiency, and the consumed power is closely related to displacement, volumetric efficiency, working condition and friction resistance. The temperature rise range of refrigerant in the motor cavity of air-cooled semi-sealed compressor is about15 "45℃ ... In air-cooled compressor, the refrigeration system does not pass through the winding, so there is no motor heating problem. 3. The compression ratio is too high. The exhaust temperature is greatly influenced by the compression ratio. The higher the compression ratio, the higher the exhaust temperature. Reducing the compression ratio can obviously reduce the exhaust temperature, and the specific methods include increasing the suction pressure and reducing the exhaust pressure. The suction pressure is determined by evaporation pressure and suction pipe resistance. Increasing the evaporation temperature can effectively increase the suction pressure, quickly reduce the compression ratio, and thus reduce the exhaust temperature. Some users think that the lower the evaporation temperature, the faster the cooling rate. There are actually many problems with this idea. Although lowering the evaporation temperature can increase the freezing temperature difference, the refrigeration capacity of the compressor decreases, so the freezing speed is not necessarily fast. What's more, the lower the evaporation temperature, the lower the refrigeration coefficient, but the load will increase, the running time will be prolonged and the power consumption will increase. Reducing the resistance of the return air duct can also increase the return air pressure. The specific methods include replacing the dirty return air filter in time and shortening the length of evaporation pipe and return air pipeline as much as possible. In addition, insufficient refrigerant is also a factor of low suction pressure. Refrigerant leakage should be replenished in time. Practice shows that it is simpler and more effective to reduce the exhaust temperature by increasing the suction pressure than other methods. The main reason of high exhaust pressure is high condensation pressure. Insufficient cooling area of condenser, scaling, insufficient cooling air or water, too high temperature of cooling water or air, etc. Will lead to excessive condensation pressure. It is very important to choose an appropriate condensation area and maintain sufficient cooling medium flow. Compared with the high-temperature air-conditioning compressor, the designed operating compression ratio is relatively low, the compression ratio doubles after freezing, and the exhaust temperature is high, but the refrigeration can't keep up, resulting in overheating. It is necessary to avoid using the compressor beyond the scope and make the compressor work at the lowest possible pressure ratio. In some cryogenic systems, overheating is the main cause of compressor failure. 4. Anti-expansion and gas mixing After the intake stroke begins, the high-pressure gas trapped in the cylinder gap will have a reverse expansion process. After the reverse expansion, the gas pressure returns to the suction pressure, and the energy consumed by compressing this part of gas is lost in the reverse expansion. The smaller the gap, the smaller the power consumption caused by expansion prevention and the greater the suction capacity, thus greatly improving the energy efficiency ratio of the compressor. In the process of reverse expansion, the gas contacts with the high-temperature surfaces of the valve plate, piston top and cylinder top to absorb heat, so the gas temperature will not drop to the suction temperature at the end of reverse expansion. After reverse inflation, the real inhalation process begins. After the gas enters the cylinder, on the one hand, it is mixed with anti-expansion gas, and the temperature rises; On the other hand, the mixed gas absorbs heat from the wall. Therefore, the gas temperature at the beginning of the compression process is higher than the suction temperature. However, due to the short time of anti-swelling process and pumping process, the actual temperature rise is very limited, usually below 5℃. Anti-expansion is caused by cylinder clearance, which is an inevitable shortcoming of traditional piston compressor. If the gas at the valve plate outlet cannot be exhausted, reverse expansion will occur. The disc valve plate and exhaust valve plate patented by Gulen Company are very special, which can eliminate the gap between exhaust hole and gas retention and fundamentally control inflation. Since its invention, the disc valve compressor has maintained the record of the highest efficiency. 5. The thermal properties of refrigerants with different compression temperature rise and refrigerant types are different, and the exhaust air temperature rise is different in the same compression process. Therefore, different refrigerants should be selected for different refrigeration temperatures. Figure 1-3 shows the temperature rise caused by adiabatic compression of different refrigerants when the condensation temperature is 50 C and the return air superheat is 20°C. Considering that the return air superheat is 20°C and the motor fever is 30°C, the theoretical exhaust temperature will exceed150 C, which requires additional cooling. For evaporation temperature above 0 C (such as air conditioning), the exhaust temperature should not exceed110 C, so there is no overheating problem. Conclusion It is suggested that overheating phenomena such as high motor temperature and high exhaust temperature should not occur in the normal operation of the compressor. Overheating of the compressor is an important fault signal, indicating that there is a serious problem in the refrigeration system or that the compressor is improperly used and maintained. If the source of compressor overheating lies in the refrigeration system, the problem can only be solved by improving the design and maintenance of the refrigeration system. Replacing a new compressor cannot fundamentally eliminate the overheating problem.