Fabrication On Domestic Refrigerator

4.3    EVAPORATOR
The evaporator is that part of refrigerating system where heat is removed from the product to be cooled. It is also called cooling coil.
As the refrigerant enters the passage of the evaporator it absorbs heat from the product it begins to boil and vaporizes. In this process, the evaporatoraccomplishes the purpose of the system refrigeration William, (2005).
There are two (2) classification of evaporator
1.    Base on operating condition
i.    Flooded type evaporator
ii.    Dry or direct expansion type
2.    Base on construction of the surface
i.    Bare tube evaporator
ii.    Plate surface evaporator
iii.    Finned surface evaporator
The direction or dry expansion coil is design for complete evaporation of the refrigerant of the refrigerant in the coil itself with only a vapour leaving the coil it will reach the compressor m superheated condition, picking up additional heat as it pass through the suction line. In the most present vary refrigeration application low temperature must maintained so that product may be kept in frozen storage condition. These frozen product cause accumulation of frost in the cooling unit, this reduce the temperature of the evaporator surface below requirement to evaporate the refrigerant. To avoid this, plated type evaporator is employed Anderson Oscar Edward, (1 972). The capacity of arm direct expansion ( DX) coil depend upon:
    The temperature of the refrigerant circulated
    The temperature of the air circulated through the coil
    The volume of air being circulated.
FACTOR AFFECTING THE VAPOUR1ZATION OF A LIQUID
The thermostat is a device used in vapour compressor refrigeration system for cycling the compressor. It is used to control the source of heatand cooling directly or indirectly to maintain a desired temperature condition. To be able to perform the function, the thermostat has a sensing abetment and a transducer. The transducer converts the effect produce by the sensing clement in to a suitable control of the device which affects the temperature.
These are the two main types of thermostat they are:
1.    Temperature actuated
2.     Pressure actuated
In the metallic type selected for the project, a brass metal is allocated at a point here control is desired and the device is place in a convenient location.
The metal element sense and relag the temperature change the electrical contact. A decrease in temperature will cause the contact to open.