4.50 refrigerant 134a enters a heat exchanger in a refrigeration system operating at steady state as saturated liquid at −18°c and exits at −6°c at a pressure of 1.4 bar. a separate air stream passes in counterflow to the refrigerant 134a stream, entering at 50°c and exiting at 25°c. the outside of the heat exchanger is well insulated. neglecting kinetic and potential energy effects and modeling the air as an ideal gas with constant cp