Solutions Manual to accompany Fundamentals of Engineering Thermodynamics 6th edition 9780471787358

Consider the Vapor compression refrigeration system from Table 1.1, “Selected Areas of Application of Engineering Thermodynamics”.

The refrigerator is a commonly used household appliance to preserve perishable products by maintaining them at a low temperature than surroundings where bacteria and fungus cannot grow. Refrigerator achieves low temperature by the use of a refrigerant, and an arrangement of a compressor, condenser, expansion device and an evaporator.

The Working of a Vapor Compression refrigeration system is explained below:

Most of the refrigerators operate on a vapor compression cycle. Initially, the refrigerant enters the compressor as a low-pressure vapor, which is at or above the temperature inside the refrigerator. The vapor is then compressed to a high-pressure, high-temperature vapor. This vapor now passes through the condenser, a series of winding tubes which are exposed to the air (usually on the backs of refrigerators). The refrigerant losses its heat to the surrounding air and gets converted into liquid refrigerant at high pressure.

This high pressure liquid refrigerant flows through the expansion device, usually a thin and long tube of copper. Throttling process occurs inside the expansion device; as a result it loses its pressure and temperature. This low temperature refrigerant is sent through the evaporator where the cooling effect is to be produced. The low temperature refrigerant absorbs the heat from the refrigeration space and maintains low temperature.

After absorbing the heat, the refrigerant again enters the compressor and the cycle continues. The refrigerant used normally used is R-134a or R-22, to help absorb and dispel heat. The thermodynamic processes that occur during the refrigeration are compression, condensation, expansion and evaporation. The efficiency of the refrigerator is measured in terms of COP (Coefficient of Performance) and its value is always greater than 1.