Given that the thermal conductivity of aluminum is 200 WmK convection

# Given that the thermal conductivity of aluminum is

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Imm. Given that the thermal conductivity of aluminum is 200 W/mK, convection coefficient is 15 W/m2K ambient temperature is 25°C, determine the following: (a) The fin efficiency and fin resistance, (b) The thermal resistance of the heat sink, (c) The temperature of the transistor when the power dissipation is 5W Assume steady-state conditions, uniform isotropic properties, no thermal contact resistance, and neglect radiation heat transfer. and the := "'2. C/ - - AI ~ g /1-1 -::= 11/4 r- 4~ 116..::= tr-{Zr-!/6)/!==- 2';?7r-/t>-~A< 4 t- ==- ;g ~ /' ;' J >,-1 t;>--f/ --r f?7 r/ Z?-~ {J-I- .:= r \ 7t:?? y/ (/ -1 ~2. 'll? :=- / - ;V~ /;- f.+) /I~ (! .=- I - ?"r. /.8,} )L/O~f' II-C?, PJ""6') 1,7 , f)£/0-1 C I '1 ~ -= 0' 'f / bb ;eo ==- (1<7 Iff-i)-I.=- / t?fJ?~y 1'7'7.?~/.»-1 t /t;;>1 vi !( b -:::; :5 7, 5 k/ft/ t<. = _4 t f'i/fI) = ~ c1.2)x/ t/ f -= lJ. 0'1;- S- G Zrr~!I 27rXbOO"K 10 z"::=- j!-- 2A. '+ 2 5) = S-;-< 5 ?-J ..,.. 2.5" =2/ '" c :; Question 3 (25 pts) ~~Q2m ~=~2m Pressurized steam at 137°C flows through a long, thin walled pipe of 0.1 m diameter. A second pipe carries pressurized cold water at a temperature of woe. The pipes are enclosed in a concrete casing that is of cylindrical cross section and 0.2 m in diameter. The axis of the pipe is centered in the casing, and the outer surface of the casing is exposed to conduction through the ground. Assume steady-state, uniform, isotropic properties. (a) List all assumptions, (b) Determine the thermal resistance of the concrete and that of the ground between the pipe, per unit length, (c) Determine the heat transfer between the pipes, per unit length. W/mK. J L IV =- 2 - = ) #### You've reached the end of your free preview.

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• Fall '08
• Staff
• Thermodynamics, Heat Transfer, Thermal conductivity, heat sink, Uniform volumetric heat, uniform thermal conductivity
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