Miscellaneous Physical Properties Process Equipments

Refrigerants – Basic Requirements

A refrigerant is a compound used in the refrigeration process that goes under a phase change from a gas to liquid and then back. Refrigerants can be found in household refrigerators as well as several commercial and industrial applications.

Different types of refrigerants can be used for specific applications and requirements.

Some of the most important things to consider while selecting a refrigerant are listed below:

  • The refrigerant must not be poisonous. In case this is not possible, the refrigerant must have a characteristic odor or contain a tracer element so that its leakage can quickly be observed.
  • The refrigerant must not be flammable or explosive. Where this condition cannot be met, a distinctive odor has to be given to the refrigerant and relevant regulations to be applied.
  • The refrigerant must be environmentally friendly. All refrigerants are characterized by the following two numbers: ODP (Ozone Depletion Potential) and GWP (Global Warming Potential). The lower these values are, the more environmentally friendly a refrigerant is.
  • The refrigerant must be kept under reasonable pressure, preferably a little higher than atmospheric pressure at the temperatures required in the evaporator.
  • To avoid expensive design, the pressure, corresponding to normal condensing pressure, must not be too high.
  • High evaporating temperature is generally desirable so that heat transmission can occur with lowest possible circulating refrigerant.
  • The refrigerant must be chemically stable at the temperatures and pressures typically expected to be encountered in a refrigeration plant.
  • The refrigerant must not be corrosive or attack normal design materials.
  • The refrigerant must not break down lubricating oil.
  • The refrigerant must be easy to obtain and handle.
  • The cost of the refrigerant must not be too high.

Of course, not a single refrigerant can meet all above mentioned requirements. Therefore, selection of the refrigerant to be used is most of the times project-specific and demands careful consideration.

Figure 1 - Typical compressor used in household or commercial refrigeration systems

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