Answer
a) $COP_R=4.33$
b) $COP_{R,max}=26.91$
c) $\dot{V}_{1,min}=12.9\ L/min$
Work Step by Step
From tables A-11 to A-13, at the compressor:
Inlet ($P_1=0.4\ MPa, x_1=1$): $v_1=0.05127\ m³/kg,\ h_1=255.61\ kJ/kg$
Outlet ($P_2=1.2\ MPa, T_2=70°C$): $h_2=300.63\ kJ/kg$
$\dot{m}_r=\dot{V}_1/v_1$
Given $\dot{V}_1=80\ L/s$
$\dot{m}_r=0.02601\ kg/s$
$\dot{W}_i=\dot{m}_r(h_2-h_1)$
$\dot{W}_i=1.171\ kW$
$\dot{Q}_L=250\ kJ/min+900W$
$\dot{Q}_L=5.067\ kW$
$COP_R=\dot{Q}_L/\dot{W}_i$
$COP_R=4.33$
$COP_{R,max}=\dfrac{1}{1-\frac{T_L}{T_H}}$
With $T_L=23°C,\ T_H=34°C$:
$COP_{R,max}=26.91$
$COP_{R,max}=\dot{Q}_L/\dot{W}_{i,min}$
$\dot{W}_{i,min}=0.1883\ kW$
$\dot{W}_{i,min}=\dot{m}_{r,min}(h_2-h_1)$
$\dot{m}_{r,min}=0.004182\ kg/s$
$\dot{m}_{r,min}=\dot{V}_{1,min}/v_1$
$\dot{V}_{1,min}=0.0002144\ m³/s=12.9\ L/min$
