In terms of economic exploitation, it is desirable that the refrigerant physical and thermophysical characteristics that minimize energy needs of the system, providing high coefficient of performance. The most important qualities of the refrigerant, which affect the system's capacity and effectiveness are:
its latent heat of vaporization
specific volume of steam
the specific heat of the refrigerant in the liquid and vapor phases
High latent heat of combustion is desirable in the refrigerant, because it reduces the mass flow rate required per unit of power. High latent heat value is accompanied by a low vapor specific volume, efficiency and productivity of the compressor is greatly enhanced. Low values of the specific volume decrease the displacement compressor is required in addition to the energy required to produce a unit of the refrigeration effect. This allows die the use of more compact equipment for a given system design.
In smaller systems, the refrigerant with low heat in a liquid state, accompanied by high specific heat in gaseous state (preferably in diat both characteristics increase the refrigerating effect per unit mass of the refrigerant.
high specific heat for steam decreases die overheating effect is experienced by the refrigerant in the evaporator to the compressor suction line and. low specific heat of the liquid increases subcooiing effect in the condenser, the receiver and the liquid line. Similarly, when both of these features are in one fluid efficiency liquid suction heat exchanger improves. There is a limit to the benefits of a high value of the refrigerating effect of the refrigerant. If the refrigerating effect is too high, the amount of the refrigerant, it is reduced to a level that is insufficient To maintain the accuracy of batching of liquid refrigerant in the evaporator.
Because the power required per unit of cooling capacity is almost die for the most commonly used refrigerants, die decisive factors in the choice of refrigerant rarely efficiency and economy of operation. More important factors when choosing a refrigerant for this application:
environmental impact from spills
the safety of people and the product is exposed to refrigerant
refrigerant properties, reduce the size, weight and cost of the equipment
characteristics that will minimize maintenance of equipment
the cost and availability of refrigerant
The refrigerating capacity and power requirements compared to R-12, R-22 and R-502 in the operating system with an open type of piston compressor. These were the most popular chlorofluorocarbon refrigerants in use before the Montreal Protocol, which has now replaced the more environmentally friendly refrigerants...
Refrigerants