problem4-24

# problem4-24 - PROBLEM 4.24 KNOWN Long fin of aluminum alloy...

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PROBLEM 4.24 KNOWN : Long fin of aluminum alloy with prescribed convection coefficient attached to different base materials (aluminum alloy or stainless steel) with and without thermal contact resistance at the unction. t,j R ′′ j FIND : (a) Heat rate q f and junction temperature T j for base materials of aluminum and stainless steel, (b) Repeat calculations considering thermal contact resistance, R , and (c) Plot as a function of h for the ange 10 h 1000 W/m 2 K for each base material. r SCHEMATIC : 1 mm ASSUMPTIONS : (1) Steady-state conditions, (2) Constant properties, (3) Infinite fin. PROPERTIES : (Given) Aluminum alloy, k = 240 W/m K, Stainless steel, k = 15 W/m K. ANALYSIS : (a,b) From the thermal circuits, the heat rate and junction temperature are bb f tot b f TT q RR R −− == ++ R f (1) (2) jf q R =+ and, with P = π D and A c = π D 2 /4, from Tables 4.1 and 3.4 find () 1 b b R 1 Sk 1 2Dk 2 0.005m k = × × 2 52 c R R A 3 10 m K / W / 0.005m / 4 1.528K / W π ⎡⎤ × = ⎢⎥ ⎣⎦ 1/2 3 22 fc R hPkA 50W m K 0.005m 240W m K 4 16.4K W

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problem4-24 - PROBLEM 4.24 KNOWN Long fin of aluminum alloy...

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