Assign6_solution_v3.pdf

# Assign6_solution_v3.pdf - Problem 1 Thi = 100 C Tci = 8 C...

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Problem # 1 8 C ci T = 28 C co T = 100 C hi T = 50 C ho T = Solution The exchanger is a 1-2 shell and tube exchanger. We want to use the LMTD method to solve the problem. (a) The heat transfer rate is obtained from the energy balance of the oil, because the total mass flowrate is known. ( )( )( ) 6 ( ) 10 2000 100 50 1 10 W p i o q mC T T = = = × (b) The mass flowrate of the brine is also obtained from an energy balance. ( ) p o i q mC T T = ( )( ) 6 kg 1 10 4200 28 8 11.9 s m m × = = (c) The overall heat transfer coefficient based on the outside area is: ln 1 1 1 2 o o o i i o o D Di U A h A kL h A = + + π o o A D L = π and i i A D L = π The inside heat transfer coefficient can be calculated from the Dittus-Boelter equation: 0.8 0.4 0.023 0.4(heating) Nu Re Pr n = = The Reynolds number is: ( ) ( ) ( ) ( ) 3 3 1.5 15 10 1000 1 10 m D U D Re × ρ = = m × 22,500 D Re = The Nusselt number is 108.22 Nu = The heat transfer coefficient is:

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