Chapter 6 - The Second Law of Thermodynamics - Problems - Page 320: 6-103E

a) $\dot{W}_i=2.71\ hp$ b) $\dot{W}_i=1.43\ hp$

a) $COP_{HP}=\dfrac{1}{1-\frac{T_L}{T_H}}$ Given $T_H=78°F,\ T_L=25°F$ $COP_{HP}=10.15$ $COP_{HP}=\dot{Q}_H/\dot{W}_i$ With $\dot{Q}_H=70000\ Btu/h$ $\dot{W}_i=2.71\ hp$ b) $COP_{HP}=\dfrac{1}{1-\frac{T_L}{T_H}}$ Given $T_H=78°F,\ T_L=50°F$ $COP_{HP}=19.2$ $COP_{HP}=\dot{Q}_H/\dot{W}_i$ With $\dot{Q}_H=70000\ Btu/h$ $\dot{W}_i=1.43\ hp$