The nature of Refrigerant

The nature of the refrigerant that must be met for the cooling needs of the engine are:
- Evaporation pressure must be high enough.
Should have a temperature of refrigerant at a higher pressure, so as to avoid the possibility of a vacuum in the evaporator and the drop in volumetric efficiency due to higher compression ratio.
- Condensation pressure is not too high.
If the condensation pressure is too low, then the compression ratio will be lower, so the performance is decreasing condenser can be avoided, but that with a lower working pressure, the machine can work more safely because of the possibility of leaks, damage, explosions and so become smaller.
- Latent heat of vaporization to be high.
Refrigerants that have a high latent heat of vaporization is more advantageous due to the same refrigeration capacity, the amount of circulating refrigerant becomes smaller.
- Specific volume (especially in the gas phase) is quite small.
Refrigerant with a large latent heat of vaporization and specific gas volumes are small (large density) will allow the use of piston compressors with volume smaller steps. Thus for the same refrigeration capacity of the refrigeration unit of the relevant size becomes smaller. However, for units of a small centrifugal water chillers refrigerant preferably with a rather large specific volume. It is necessary to increase the amount of circulating gas, so as to prevent further loss of efficiency centrifugal compressors.
- Coefficient of achievement should be high.
In terms of thermodynamic characteristics of refrigerants, coefficient of achievement is the most important parameter for determining the operating costs.
- High thermal conductivity.
Thermal conductivity is very important to determine the heat transfer characteristics.
- Low viscosity in the liquid phase and gas phase.
With the decrease in refrigerant flow resistance in the pipe, the pressure loss will be reduced.
- The dielectric constant of refrigerant small, large electrical resistance, and does not cause corrosion on the electrical insulator material. The properties mentioned below are very important, especially for the refrigerant to be used in hermetic compressors.
- Refrigerant should be stable and do not react with the materials used, so it does not cause corrosion.
- Refrigerant must not be toxic and odorless stimulating.
- Refrigerant must not be flammable and explosive
Boiling point is the temperature (temperature) where the vapor pressure of a liquid equals the external pressure experienced by the fluid. A liquid in a vacuum will have a lower boiling point than when the liquid that was in the atmosphere pressure. Fluid inside the high pressure will have a boiling point higher than the boiling point at the pressure of the atmosphere.
Or in other words, the boiling point is the point at which a liquid will begin to evaporate / change form.
For refrigerant has a boiling point of about -30 so that when the cooling system is suitable for this.