Unformatted text preview: ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎣ ⎡ ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ + + = Nu [ ] 2 2 m 5 . 4 ) m 5 . 3 )( m 5 . ( ) m 1 )( m 5 . ( 2 C . W/m 75 . 4 ) 84 . 89 ( m 5 . C W/m. 02644 . = + = ° = ° = = s A Nu L k h and W 1 . 748 C ) 20 55 )( m 5 . 4 )( C . W/m 75 . 4 ( ) ( 2 2 = ° − ° = − = ∞ T T hA Q s s & The radiation heat loss is [ ] W 9 . 750 ) K 273 20 ( ) K 273 55 ( ) .K W/m 10 67 . 5 )( m 5 . 4 )( 7 . ( ) ( 4 4 4 2 8 2 4 4 = + − + × = − = − surr s s rad T T A Q σε & Then the total rate of heat loss becomes W 1499 = + = + = 9 . 750 1 . 748 rad convection natural total Q Q Q & & & The amount and cost of the heat loss during one year is kWh 131 , 13 h) 8760 )( kW 499 . 1 ( = = Δ = t Q Q total total & $1116 = = ) kWh / 085 . )($ kWh 131 , 13 ( Cost 915...
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 Fall '10
 Dr.DanielArenas
 Thermodynamics, Convection, Mass, Heat, Heat Transfer, heat loss, Nusselt number

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