State the factors to be considered while selecting refrigerants.
Selection criteria for refrigerant :
1. Working pressure range and pressure ratio. The pressure required to be maintained in the evaporator and condenser should be low enough to reduce the material cost and must be positive to avoid leakage of air into the system. 2. Corrosiveness and flammability: Non corrosive to mechanical components. It should be safe to operate(including non-toxic, nonflammable) 3. Space limitations: It should have low specific volume to reduce the size of the compressor. 4. Temperature required in the evaporator: It should have low boiling point and low freezing point. 5. Oil miscibility. It should have high miscibility with lubricating oil and it should not have reacting property with lubricants. 6. It should not have any bad effect on the stored material or food when any leak develops in the system. 7. It should have low thermal conductivity to reduce the area of heat transfer in the evaporator and condensers. 8. It should have high critical pressure and temperature to avoid large power requirement. 9. It must have low specific heat and high latent heat. 10. It should have moderate density in liquid form, a relatively high density in gaseous form.