Fabrication On Domestic Refrigerator

4.7    THERMODYNAMIC ANALYSIS
A refrigerant is a device that absorbs heat through expansion and vaporization and loses it through condensation in the refrigerating system is also a substance which act as a cooling agent by absorbing heat from another body and reject it elsewhere. However, only those substances that can undergo change at useful temperature and pressure are of practical value, Before a substance could be chosen as refrigerant for a particular application it must possess certain properties that make it suitable. The most frequently used refrigerant in modern day refrigeration system is: R12, R22, R502 and R134.
4.8    SELECTING REFRIGERANT
    The refrigerator capacity
    The type of compressor used (generally reciprocating, centrifugal or screw).
    The refrigeration temperature required
4.8.1    Classification of Refrigerant
These refrigerant are classified as follows
    Primary refrigerant
    Secondary refrigerant
4.8.2    Primary Refrigerant
Those are working medium or heat carries which directly takes part in the refrigeration and cool the substance by the absorption of latent heat e.g ammonia, carbondioxide, etc.
Primary refrigerant are further classified in to the following groups:
    Halocarbon compound
    Hydrocarbon
    Inorganic compound
    Unsaturated compound
483 Secondary Refrigerant
These are those circulating substance which are first cooled with the help of the primary refrigerant and are then employed for cooling purpose eg ice, carbon dioxideetc these refrigerants cool substances bi absorption of their sensible heat.
4.8.4    Desirable Properties of Ideal Refrigerant
An ideal refrigerantposses the following properties
A.    Thermodynamic properties
B.    Physical properties
C.    Other properties
4.8.4.1 Thermodynamic Properties of a Refrigerant
    Low boiling point
    Low freezing point
    Positive pressure in evaporator and condenser
    High saturated temperature
    High latent heat of vaporization