3. Refrigerant-134a at 1 MPa and 90 C is to be cooled to 1 MPa and 30 C in a condenser by air. The air enters at 100 kPa and 27 C with a volume flow rate of 600 m/min and leaves at 95 kPa and 60 C. Determine the mass flow rate of the refrigerant. (35 pts) Assumptions 1 This is a steady-flow process since there is no change with time. 2 Kinetic and potential energy changes are negligible. 3 There are no work interactions. 4 Heat loss from the device to the surroundings is negligible and thus heat transfer from the hot fluid is equal to the heat transfer to the cold fluid. 5 Air is an ideal gas with constant specific heats at room temperature. Take the gas constant of air to be 0.287 kPa m/kg.K. NB: Take the entire heat exchanger as the control volume (i.e. the boundary is outside the heat exchanger) Air V3 = 600 m/min 100 Pal 15