The following figure shows the schematic diagram of a vapor compression refrigeration system using r-134a as the working fluid. This arrangement is used to achieve refrigeration at two different temperatures with a single compressor and a single condenser. The low-temperature evaporator operates at -18°C with saturated vapor at its exit and has a refrigerating capacity of 3 tons. The high-temperature evaporator produces saturated vapor at 3.2 bar at its exit and has a refrigerating capacity of 2 tons.
Compression is isentropic to the condenser pressure of 10bar. There are no significant pressure drops in the flows through the condenser and the two evaporators, and the refrigerant leaves the condenser as saturated liquid at 10 bar. Draw cycle on a T-S diagram and determine:
a) The mass flow rate of refrigerant through each evaporator, in kg/min
b) The compressor power input, in kW
c) The rate of heat transfer from the refrigerant passing through the condenser, in kW