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Problems-heat

# Problems-heat - Heat Transfer(Problem 14-2 in PT&W At an...

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Heat Transfer (Problem 14-2 in PT&W) At an average film T of 350 K, what are theindividual heat-transfer coefficients when thefluid flowing in a 0.0254 m ID tube is air, water or oil? TheReis 5 x 10 4 for all of thesefluids. How would thepressure drop vary for each fluid ? At 350 K, the properties of the fluids areas follows: Air Water Oil Density, Kg/m 3 0.955 973 854 Viscosity, Pa . s 2x10 -5 3.72x10 -4 3.56x10 -2 Thermal conductivity, W/m . K 0.030 0.668 0.138 Heat capacity, J/kg . K 1050 4190 2116 ChE 4253 - Design I

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Heat Transfer (Problem 14-2 in PT&W) Need to use the Sieder-Tate correlation with C=0.023 h = (k/D) 0.023 Re 0.8 Pr 0.33 Air h = 0.03/0.0254 0.023 (5x10 4 ) 0.8 * (1050 2x10 -5 / 0.03) 0.33 = 138.6 W/m 2. K Water h = 0.668/0.0254 0.023 (5x10 4 ) 0.8 * (4190 3.72x10 -4 / 0.668) 0.33 = 4610 W/m 2. K Oil h=5869 W/m 2. K ChE 4253 - Design I 14 . 0 33 . 0 8 . 0 Pr Re = w C Nu μ μ
Heat Transfer (Problem 14-2 in PT&W) Pressure drop dueto friction: The Fanning factor the same for all, since Re=const. Wecan calculatethevelocity in each pipefrom thedefinition of theRe, V=Re μ /(D ρ ) Air V = 41.22 m/s Water V = 0.75 m/s Oil V = 83 m/s Pressuredrop per unit length (assumef=0.008): Air 1022 N/m 2 Water 344 N/m 2 Oil 3.7x10 6 N/m 2 ChE 4253 - Design I ρ ρ L D f V F 2 2 =

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