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Q21. A vapour compression cooling cycle using CO₂ operates between pressures of 18.5089 bar and 68.9182 bar. The refrigerant enters the compressor at a temperature of -18°C and leaves the condenser as saturated liquid. The temperature at compressor outlet is 103°C.

(a) Sketch the cycle on a p-h diagram. (3)

(b) Using Barasheet Q6, determine the coefficient of performance of the cycle. (6)

(c) State TWO disadvantages and THREE advantages of CO₂ as a refrigerant compared with other refrigerants such as halocarbons, hydrocarbons and ammonia. (7)