Problem 4.9 - A Home Air Conditioner & Hot Water Heater

We wish to do a preliminary thermodynamic evaluation of a 500W input power home heat pump system as applied to summertime use for both hot water heating to 50°C, and space cooling (air conditioning), and thus maintain the inside home temperature at a comfortable 20°C..


This unique combined air conditioning / hot water heating system is designed to absorb heat from the air flowing through the insulated duct in order to pump heat into the hot water heating tank. The fan provides enough air flow over the evaporator to cool the air by 10°C as it passes through the duct, and the hot water is heated to a maximum of 50°C. In this analysis we neglect the power provided to the fan. We also assume that both the duct and the hot water tank are externally adiabatic.

Carefully draw the complete cycle above on the pressure-enthalpy [P-h] diagram provided below, showing clearly all five processes (1) - (2) - (3) -(4) - (5) -(1). Using the conditions shown on the diagram above and values obtained from the R134a tables: