Chapter 6 - The Second Law of Thermodynamics - Problems - Page 320: 6-104

a) $\Delta t=5.90\ h$ b) $C=\$3.11$ c) $C_r=\$40.3$

$COP_{HP}=\dfrac{1}{1-\frac{T_L}{T_H}}$ Given $T_H=25°C,\ T_L=2°C$ $COP_{HP}=12.96$ $Q_H=\dot{Q}_H\Delta t$ With $\Delta t = 1day,\ \dot{Q}_H=55000\ kJ/h$ $Q_H=1320\ MJ$ $COP_{HP}=Q_H/W_i$ $W_i=101.88\ MJ$ $W_i=\dot{W}_i\Delta t$ With $\dot{W}_i=4.8\ kW$: $\Delta t=5.90\ h$ $C=W_i\times p$ With $p=\$0.11/kWh$ $C=\$3.11$ $C_r=Q_H\times p$ $C_r=\$40.3$