Air enters a counterflow heat exchanger operating at steady state at 22°C, 0.1 MPa and exits at 7°C. Refrigerant 134a enters at 0.2 MPa, a quality of 0.2, and a mass flow rate of 30 kg/h. Refrigerant exits at 0°C. Stray heat transfer is negligible and there is no significant change in pressure for either stream.
(a) For the Refrigerant 134a stream, determine the rate of heat transfer, in kJ/h.
(b) For each of the streams, evaluate the change in flow exergy rate, in kJ/h, and interpret its value and sign.
Let T0 5 22°C, p0 5 0.1 MPa, and ignore the effects of motion and gravity.