10.23 Figure P10.23 shows a two-stage vapor-compression refrigeration system with ammonia as the working fluid. The syst
Posted: Thu May 26, 2022 11:27 am
10.23 Figure P10.23 shows a two-stage vapor-compression refrigeration system with ammonia as the working fluid. The system uses a direct contact heat exchanger to achieve intercooling. The evaporator has a refrigerating capacity of 30 tons and produces -30°C saturated vapor at its exit. In the first compressor stage, the refrigerant is compressed adiabatically to 0.55 MPa, which is the pressure in the direct contact heat exchanger. Saturated vapor at 0.55 MPa enters the second compressor stage and is compressed adiabatically to 1.7 MPa. Each compressor stage has an isentropic efficiency of 85%. There are no significant pressure drops as the refrigerant passes through the heat exchangers. Saturated liquid enters each expansion valve. Determine (a) the ratio of mass flow rates, m3/m₁. (b) the power input to each compressor stage, in kW. (c) the coefficient of performance. (d) Plot each of the quantities calculated in parts (a)-(c) versus the direct-contact heat exchanger pressure ranging from 0.14 to 1.4 MPa. Discuss.