Correct Answer - Option 4 : collect the liquid refrigerant and preclude its reversion to the compressor
The evaporator is the component of the refrigerator where heat is removed from the substance which needs to be kept cool. It is classified mainly as flooded and dry evaporators.
Flooded Evaporators: In this liquid refrigerant covers the entire heat transfer surface and the float valve are used for the expansion of refrigerant. Due to heat supplied by the substance to be cooled, the liquid refrigerants gets evaporated and the liquid level falls. To maintain the constant level of liquid the float valve opens and admits more liquid. As the evaporator is filled with liquid the evaporators are not superheated but as at saturation. To prevent the liquid carry over to the compressor accumulators are used with flooded evaporators.
Direct Expansion (Dry Evaporators): In dry evaporators, a part of the heat transfer surface is used for superheating the vapor. Thermostatic valves are used in this type of evaporator. The long length of bare or finned pipes is used to cool air or liquid flowing across it while the refrigerant. The refrigerant expands directly inside the tubing, and evaporates, thus cooling the medium outside. The liquid refrigerant is evaporated in the tube of the evaporator. Throttling is necessary to boil the refrigerant at lower pressure.
