Marine Engineering Study Materials

Following are the desirable properties of a primary refrigerant.

1. The liquid has to vapourise at the evaporator coil to cause cooling. The liquid at the evaporator coil should therefore vapourise easily, otherwise the compressor will have to create too much of vacuum to cause the liquid to vapourise. Thus, ‘Boiling Point’ of the refrigerant should be low.
2. Pressure to which compressor has to compress the drawn gases, to convert them back into liquid at the condenser, should be low. Therefore the refrigerant vapors should be easily condensible.
3. Every kilogram of liquid refrigerant vapourised at the evaporator coil should take away a large amount of heat, i.e. ‘Specific Enthalpy of Vaporisation’ (latent heat) of refrigerant should be high. Otherwise mass flow rate will be high.
4. Once the evaporated gas is compressed, the temperature of seawater should be low enough (below critical temperature of the refrigerant) to be able to condense these gases to liquid form. Thus ‘Critical Temperature’ of the refrigerant should be high.
5. Vapor produced after vapourisation of the liquid at the evaporator coil should occupy minimum volume, to keep pipeline diameter, compressor size, etc. small and compact. Thus refrigerant vapor should have low ‘Specific Volume’.
6. Non-Corrosive
7. Stable
8. Non-flammable and Non-explosive
9. Compatible with crank case oil, oil seals, gaskets, metal involved, etc.
10. Easy leak detection possible
11. Non-Toxic
12. Environmental friendly
13. Cheap
14. Easily available
15. Easily stored.