Exergy analysis of a refrigeration cycle

Assume that kinetic and potential energy changes are negligible, and the system is at steady state. 

The throttling process (Stage 4) causes partial vaporization of the saturated liquid. The vapor part of the mixture is known as quality. Using the enthalpy values at 0.293 MPa (Table 4.10a) the quality is 

For the cycle, the total enthalpy change is zero. At the compressor, outside energy Wm is needed, and at the evaporator, heat transfer qm from the matter to be cooled is used to evaporate the refrigerant R-134a. 

The heat absorbed within the evaporator from the contents of the refrigerator is 

The energy balance indicates that the total energy (IFm + qm) is removed by the cooling water. For the cycle, the first law yields 

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