a) Ambient air at 20C flows at a velocity of 10m/s parallel to a wall 5m...

 

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a) Ambient air at 20°C flows at a velocity of 10m/s parallel to a wall 5m wide and 3m high. Calculate the heat transfer rate if the wall is maintained at 40°C. If the entire boundary layer is assumed turbulent, what will be the percentage error in the computation of heat transfer rate? Comment on the comparable values of the two results. Given: Nu = 0.664Re0.5P¹/3 (for laminar flow) Nu = 0.0375Re 0.8P1/3 (for turbulent flow) Nu = 0.0375 [Re08-23200] Pr¹3 (for mixed flow) TEMPERATURE [°C] 30 50 70 Properties of air at 1 atm pressure THERMAL DENSITY p[kg/m³] 1.164 1.092 1.028 CONDUCTIVITY KW/(m.°C)] 0.02630 0.02735 0.02881 DYNAMIC KINEMATIC VICOSITY VISCOSITY u[kg/(m.s)] 1.850X10 1.963X10 2.052X105 N [m²/s] 1.589X105 1.798X10 1.995X10 PRANDTL NUMBER Pr 0.7070 0.7228 0.7177 (10 marks) a) Ambient air at 20°C flows at a velocity of 10m/s parallel to a wall 5m wide and 3m high. Calculate the heat transfer rate if the wall is maintained at 40°C. If the entire boundary layer is assumed turbulent, what will be the percentage error in the computation of heat transfer rate? Comment on the comparable values of the two results. Given: Nu = 0.664Re0.5P¹/3 (for laminar flow) Nu = 0.0375Re 0.8P1/3 (for turbulent flow) Nu = 0.0375 [Re08-23200] Pr¹3 (for mixed flow) TEMPERATURE [°C] 30 50 70 Properties of air at 1 atm pressure THERMAL DENSITY p[kg/m³] 1.164 1.092 1.028 CONDUCTIVITY KW/(m.°C)] 0.02630 0.02735 0.02881 DYNAMIC KINEMATIC VICOSITY VISCOSITY u[kg/(m.s)] 1.850X10 1.963X10 2.052X105 N [m²/s] 1.589X105 1.798X10 1.995X10 PRANDTL NUMBER Pr 0.7070 0.7228 0.7177 (10 marks)

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0 Tmean 4020 2 30C properties Tmean 121589x105ms Por07070 K00263 WmK 3146106 5105 Assu... View the full answer