Refrigerant R12 is the most widely used of all the refrigerants for different refrigeration and air conditioning applications. It is indeed very tough that any refrigerant will be able to replace this highly versatile refrigerant in different operating conditions. However, R134a has been able to replace R12 successfully in number of applications. Let us see how R134a compares well with R12.
1) Power required per ton of refrigeration: For the evaporator temperatures of -7 degree C and above the isentropic discharge temperature from the compressor for both the refrigerants is same. The total horsepower required per ton of refrigeration is also same. For the temperatures below -7 degree C, if R12 is replaced by R134a there will be significant loss of the refrigerating effect, and in such cases it is advisable to use the blends of refrigerants as the replacement instead of using R134a.
2) Low temperature application: For the instance where the saturation temperature is -15.08 degree F at the standard barometric pressure, and if the evaporator temperature is below 0 degree F, the pressure in the evaporator will be still well above the vacuum Thus the refrigerant R134a can be used for the low temperature applications also without the need to produce vacuum in low pressure side of the refrigeration system.
3) Heat transfer coefficients: The heat transfer coefficients for refrigerant R134a are higher than R12 in different conditions depending on the temperature. If the refrigerants exist in single liquid phase the heat transfer coefficient of R134a is higher by 27 to 37% and if they are in gaseous phase it is higher by 37 to 45%. If the refrigerants exist in two phases, liquid and gaseous, the heat transfer coefficient for R134a is higher by 28 to 34% in the evaporator and 35 to 41% in the condenser.
