Chapter 1, Problem 1.39P

A household refrigerator operates with cold- andhot-temperature reservoirs et $T_c=5°\text{C}$ and $T_h=25°\text{C}$ , respectively. When new, the cold and hot side resistancesare $R_{c,n}=0.05\text{K/W}$ and $R_{h,n}=0.04\text{K/W}$ , respectively.Over time, dust accumulates on the refrigerator’s condenser coil, which is located behind the refrigerator, increasing the hot side resistance to $R_{h,d}=0.1\text{K/W}$ . It isdesired to have a refrigerator cooling rate of $q_{in}=750\text{W}$ .Using the results of Problem 1 .38, determine the modifiedcoefficient of performance and the required power input $\stackrel{\dot{}}{W}$ under (a) clean and (b) dusty coil conditions.