Which gas is used in chiller?

- Mar 13, 2020-

R134a is a single component refrigerant, while R407C and R410a are mixed refrigerants. R410a is a mixture of R32 and R125, and R407C is a mixture of R32, R125 and R134a. The advantage of mixed refrigerants is that according to the specific requirements of use, various properties such as flammability, capacity, exhaust temperature, and efficiency can be considered to form a refrigerant.


There are many factors to consider when choosing a refrigerant, as the choice of any refrigerant will have an impact on the overall operation, reliability, cost and market acceptance of the air conditioning system. What is of great interest to everyone is that the new refrigerants have different refrigerant transmission performance due to their different heat transfer and pressure drop, which will ultimately have a significant impact on system design and system performance. We briefly discuss the differences in performance characteristics between these common refrigerants.


R134a has a lower capacity than R22 and lower pressure than R22. Because of these characteristics, the R134a air conditioner with the same capacity needs to be equipped with a compressor with a larger displacement, a larger evaporator, condenser, and piping. The end result is that the R134a system will require higher costs to manufacture and run a system with the same cooling capacity as the R22.


The capacity and pressure of R407C refrigerant are relatively close to R22. Therefore, as long as the system design is simply adjusted, the original R22 system can also be applied to the R407C system. However, the energy efficiency ratio of the system will be reduced by about 5% compared to the original system. This is because R407C has a temperature drift of up to 6 degrees compared to other refrigerants. Therefore, the R407C system will reduce heat transfer when the same standard condenser and evaporator are used, which will affect the energy efficiency of the system.


The capacity and pressure of R410a refrigerant is higher than R22, and the operating pressure is 50% -60% higher. As a result of high pressure and high gas density, not only can a smaller displacement compressor be used, but also smaller diameter pipes and valves can be used. The use of high-pressure exhaust valves eliminates the hidden dangers of high-pressure condensation in the system. The thick compressor housing subjects the system to higher operating pressures. Another advantage of making the compressor heavier is that the operating noise of the R410a is significantly lower than that of the R22 compressor by 2-4 decibels.


Compared with the R22 system, the R410a refrigerant system has a significant heat transfer advantage-the heat transfer of the evaporator is 35% higher, and the condenser is 5% higher. The heat transfer coefficients of R134a and R407C are lower than R22. At the same mass flow rate, the pressure drop of R410a is small, making it possible to use smaller pipes and valves than R22 or other refrigerants. This will be more likely to reduce the cost of materials for manufacturing the R410a system and is more advantageous in long-piping home appliances and multi-line systems. Of course, only by redesigning the system can we fully take advantage of the small heat transfer and pressure drop of the R410a-for example, you can consider adopting the following optimization techniques, using smaller diameter coils, different fin structures, and increasing the loop length to reduce Number of refrigeration circuits. In the end, we can see that the system redesigned for R410a refrigerant uses a smaller volume of evaporator and condenser, which has a lower cost and can reduce the refrigerant charge up to 30%. The reduction in refrigerant charge will not only reduce costs, but also improve the reliability of the entire system.


In a system with the same cooling capacity and the same condensation temperature, the system energy efficiency (COP) of R410a refrigerant can be 6% higher than R22. This is due to the lower loss of the compressor during the compression process, the stronger heat transfer of the evaporator and the condenser, and the smaller the pressure drop in the entire system. Efficient heat transfer and smaller pressure drop make it have lower condensing temperature and higher evaporating temperature under the same operating conditions, which makes the compressor achieve a better power consumption and less efficiency. Operating range. In addition, for the low compression loss characteristics of R410a, large compressors in small commercial air-conditioning systems benefit more than small domestic air-conditioning compressors.