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Unformatted text preview: . Pr Re 037 . 2 3 / 1 8 . 5 3 / 1 8 . = = = = = = = Nu L k h k hL Nu L [ ] W 1734 = C 5)(75 m) m)(0.7 (0.6 C) . W/m 97 . 58 ( ) ( 2 = = s s conv T T hA Q & The heat loss by radiation is then determined from StefanBoltzman law to be [ ] W 181 K) 273 + (10 K) 273 + (75 ) .K W/m 10 (5.67 ) m 7 . )( m 6 . )( 92 . ( ) ( 4 4 4 28 4 4 = = = surr s s rad T T A Q & Then the total rate of heat loss from the bottom surface of the engine block becomes W 1915 = + = + = 181 1734 rad conv total Q Q Q & & & The gunk will introduce an additional resistance to heat dissipation from the engine. The total heat transfer rate in this case can be calculated from W 1668 = m) 0.7 m 6 . )( C W/m. 3 ( ) m 002 . ( m)] m)(0.7 C)[(0.6 . W/m 97 . 58 ( 1 C 5)(75 1 2 + = + = s s s kA L hA T T Q & The decrease in the heat transfer rate is 17341668 = 66 W 776...
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 Fall '10
 Dr.DanielArenas
 Thermodynamics, Convection, Force, Mass, Heat

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