A household refrigerator operates with cold- and hot-temperature reservoirs of T c = 5C and T h

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A household refrigerator operates with cold- and hot-temperature reservoirs of Tc = 5°C and Th = 25°C, respectively. When new, the cold and hot side resistances are Rc,n = 0.05 K/W and Rh,n = 0.04 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 Rh,d 0.1 K/W. It is desired to have a refrigerator cooling rate of qin = 750 W. Using the results of Problem 1.38, determine the modified coefficient of performance and the required power input W under 

(a) Clean and 

(b) Dusty coil conditions.

Data From Problem 1.38

An internally reversible refrigerator has a modified coefficient of performance accounting for realistic heat transfer processes of

where qin is the refrigerator cooling rate, qout is the heat rejection rate, an W is the power input. Show that COPm can be expressed in terms of the reservoir temperatures Tc and Th, the cold and hot thermal resistances Rt,c and Rt,h, and qin, as

where Rtot = Rt,c + Rt,h. Also, show that the power input may be expressed as

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Related Book For  book-img-for-question

Fundamentals Of Heat And Mass Transfer

ISBN: 9780470501979

7th Edition

Authors: Theodore L. Bergman, Adrienne S. Lavine, Frank P. Incropera, David P. DeWitt

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