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Thin-walled aluminum tubes of diameter D = 10 mm are used in the condenser of an air conditioner....

Thin-walled aluminum tubes of diameter D = 10 mm are used in the condenser of an air conditioner. Under normal operating conditions, a convection coefficient of hi = 5000 W/m2 · K is associated with condensation on the inner surface of the tubes, while a coefficient of ho = 100 W/m2 · K is maintained by airflow over the tubes.

a. What is the overall heat transfer coefficient if the tubes are unfinned?

b. What is the overall heat transfer coefficient based on the inner surface, Ui, if aluminum annular rectangular fins of thickness t = 1.5 mm, outer diameter Do = 20 mm, and pitch S = 3.5 mm are added to the outer surface? Base your calculations on a 1-m-long section of tube.

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。〉 가e overall heat transfor coetrcc.ent the tubesaxe uumed 5000 N~+= ㆆ10035-286 (Nott fons Per unit lengt, Total fin O.00357,-0.99 The overall heat tramotex cofficie o -1 0 49x100 x0 18

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