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Q6. A vapour compression refrigeration system operates between the pressure of 2.68 bar and 10.34 bar. It produces 2 tonnes/hour of ice at -8℃ from water at 25℃.

The ammonia refrigerant enters the compressor at a temperature of 13℃. It leaves the compressor with 100 K superheat. The mass flow rate is 750 kg/hour.

(a) Calculate EACH of the following:

(i) The dryness fraction of the refrigerant entering the evaporator; (5)

(ii) The degree of undercooling in the condenser; (3)

(iii) The compressor power; (2)

(iv) The coefficient of performance. (2)

(b) Sketch The cycle on pressure-specific enthalpy and Temperature specific entropy diagrams. (4)

Note: for water specific heat capacity = 4.2 kJ⁄(kg K)

for ice specific heat capacity = 2.1 kJ⁄(kg K)

latent heat of fusion = 334 kJ⁄kg