Abstract:

Two typical types of CO₂-NH₃ cascade and NH₃ two stage compression refrigeration processes were designed and calculated.The key parameters of the two processes were compared, and the heat flow distributions of heat exchangers were also analyzed, as well as parameters optimization of the NH3 refrigeration system.The results show that in terms of evaporation temperature at -45℃, the total power consumption of compressors and NH₃ flow of the CO₂-NH₃ cascade process are less than that of the NH₃ process.But there is massive refrigeration capacity at medium temperature in NH3 process, so the COP of NH3 process is higher than that of CO₂-NH₃ process.The difference in temperature of two phase liquids in the condensation-evaporator of cascade system is less, and that in the midst cooler of NH₃ system is larger.Along with the ascending exhaust pressure of low-pressure stage compressor and the descending midst temperature, the total power consumption of the NH3 process of two stage compression will be downtrend.