A water-loop heat pump system is used to heat and cool a building with 4 zones (see Fig. E XXXXXXXXXXIf the water temperature in the loop falls below 15°C, a gas-fired furnace in the loop is activated...

A water-loop heat pump system is used to heat and cool a building with 4 zones (see Fig. E13.15.1). If the water temperature in the loop falls below 15°C, a gas-fired furnace in the loop is activated to maintain the temperature of the water at 15°C. If the temperature rises above 35°C, the water is sent through a cooling tower which maintains the water temperature at 35°C. (See Fig. 13.11.) The heating and cooling mode COPs of the heat pumps are well represented by the equations:

where tw (°C) is the temperature of the water loop. The cooling (positive) and heating (negative) loads of the zones for four different time periods are given in Table P13.12.1. Calculate (i) the total energy input rate to the heat pumps, (ii) the heat input rate to the furnace, and (iii) the heat rejection rate in the cooling tower, for the different load conditions. Neglect any effects due to storage.