In a vapour compression refrigeration cycle, the refrigerant enters the compressor in saturated vapour state at evaporator pressure, with specific enthalpy equal to 250 kJ/kg. The exit of the compressor is superheated at condenser pressure with specific enthalpy equal to 300 kJ/kg. At the

Question

In a vapour compression refrigeration cycle, the refrigerant enters the compressor in saturated vapour state at evaporator pressure, with specific enthalpy equal to 250 kJ/kg. The exit of the compressor is superheated at condenser pressure with specific enthalpy equal to 300 kJ/kg. At the condenser exit, the refrigerant is throttled to the evaporator pressure. The coefficient of performance (COP) of the cycle is 3. If the specific enthalpy of the saturated liquid at evaporator pressure is 50 kJ/kg, then the dryness fraction of the refrigerant at entry to evaporator is __________.

Accepted Answer

0.25. The dryness fraction at the entry to the evaporator can be calculated using the specific enthalpy values. Given that the specific enthalpy of the saturated liquid is 50 kJ/kg and the enthalpy of the refrigerant entering the evaporator is 250 kJ/kg, the dryness fraction is determined by the formula: x = (h - hf) / (hg - hf), where hf is the enthalpy of the saturated liquid and hg is the enthalpy of the saturated vapor. This calculation yields a dryness fraction of 0.25, indicating that 25% of the refrigerant is in vapor form.

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