Question 14
16
MEE 4042 Refrigeration Machines
2022-2023, Spring
A vapor –compression refrigeration system with a capacity of 10 tons has
superheated Refrigerant 134a vapor entering the compressor at 15 °C, 4
bar, and exiting at 12 bar. The compression process can be modelled by
Pv1.01=constant. At the condenser exit, the pressure is 11.6 bar, and the
temperature is 44 °C. The condenser is water-cooled, with water entering
at 20 °Cand leaving at 30 °C with a negligible change in pressure. Heat
transfer from the outside of the condenser can be neglected. Determine
(a) the mass flow rate of the refrigerant, in kg/s.
(b) the power input and the heat transfer rate for the compressor, each in
kW.
(c) the coefficient of performance.
(d) the mass flow rate of the cooling water, in kg/s.
(e) the rates of exergy destruction in the condenser and expansion valve,
each expressed as a percentage of the power input. Let T0=20 °C.