Thermodynamics HW Solutions 521

Thermodynamics HW - 2 2 1 2 2 2 2 1 2 2 1 2 L L T T k kL k L T T k dy dT k q L y L V V& Discussion A temperature rise of about 72.5 ° C

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Chapter 6 Fundamentals of Convection The maximum temperature is the value of temperature at this y , whose numeric value is mm 0.2174 = = + ° ° = + μ = m 0002174 . 0 2 1 m/s) 12 )( N.s/m 580 . 0 ( C ) 15 40 ( ) C W/m. 145 . 0 ( ) m 0004 . 0 ( 2 1 2 2 2 1 2 V T T k L y Then C 100.0 ° = ° + ° + ° = + + = = 2 2 2 2 2 2 2 1 1 2 max m) 0004 . 0 ( m) (0.0002174 m 0004 . 0 m 0.0002174 ) C W/m 2(0.145 m/s) 12 )( s/m N 58 . 0 ( C 5 1 m) 0002174 . 0 ( m 0004 . 0 C ) 15 40 ( 2 ) 0002174 . 0 ( L y L y k T y L T T T T V μ ( c ) Heat flux at the plates is determined from the definition of heat flux, () 2 5 W/m 10 1.135 × = ° ° = = = = = m/s N 1 W 1 ) m 2(0.0004 m/s) 12 )( s/m N 58 . 0 ( m 0004 . 0 C ) 15 40 ( ) C W/m. 145 . 0 ( 2 0 1 2 2 2 2 1 2 2 1 2 0 0 L L T T k kL k L T T k dy dT k q y V V () 2 4 W/m 10 9.53 × = + ° ° = + = = = = m/s N 1 W 1 ) m 2(0.0004 m/s) 12 )( s/m N 58 . 0 ( m 0004 . 0 C ) 15 40 ( ) C W/m. 145 .
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Unformatted text preview: ( 2 2 1 2 2 2 2 1 2 2 1 2 L L T T k kL k L T T k dy dT k q L y L V V & Discussion A temperature rise of about 72.5 ° C confirms our suspicion that viscous dissipation is very significant. Calculations are done using oil properties at 27.5 ° C, but the oil temperature turned out to be much higher. Therefore, knowing the strong dependence of viscosity on temperature, calculations should be repeated using properties at the average temperature of about 64 ° C to improve accuracy. 6-10...
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This note was uploaded on 01/22/2012 for the course PHY 4803 taught by Professor Dr.danielarenas during the Fall '10 term at UNF.

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