3.2.10. Chemical properties

3.2.10. Chemical properties

1. Flammability

It is an important characteristic in the selection of refrigerant. Ammonia and methyl chloride refrigerant will burn but are explosive under unusual conditions only. CO2, N2, NO2 and fluorocarbon are nonflammable and non-explosive.

2. Toxicity

All fluorocarbon refrigerant become toxic when mixed with certain percentage of air. Ammonia and SO2 are highly toxic and not  used in air conditioning. The use of toxic refrigerant  is limited to cold storage.

3. Miscibility

The ability of refrigerant to mix with oil is called miscibility. The degree of miscibility depends upon the temperature of oil and pressure of refrigerating vapour. The Freon group are highly miscible refrigerant while ammonia, CO2, SO2, and methyl chloride are relatively non-miscible. The non – miscible refrigerant require larger heat transfer surface due to poor heat conduction properties of oil. The miscible refrigerant give better lubrication.

4. Effect on perishable materials:

The refrigerant used in cold storage and in domestic refrigerators should be such that in case of leakage, it should have no effect on the perishable material.

The Freon group have no effect on dairy products, meats, vegetable, flowers & fruits. Methyl chloride also have no effect on materials. But SO2, ammonia affect the material.

NH4 easily dissolve in water and becomes alkaline in nature.

Since most fruits and vegetables are acidic in nature, therefore ammonia reacts with these products and spoils the taste.


Last modified: Saturday, 24 December 2011, 11:15 AM