Chapter 8: Internal Forced Convection

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General Thermal Analysis• In the absence of any work interactions, the conservationof energy equation for the steady flow of a fluid in a tubeQ = mc T −T(8-15)( ) (W)p e i• The thermal conditions at the surface can usually beapproximated as:– constant surface temperature, or– constant surface heat flux.• The mean fluid temperature T m mustchange during heating or cooling.• Either T s = constant or q s = constant at the surface of atube, but not both.
Constant Surface Heat Flux• In the case of constant heat flux, the rate of heat transfer canalso be expressed asQ = q A = mc T −T(8-17)s s p e i( ) (W)• Then the mean fluid temperature at the tube exit becomesqAs sTe= Ti+ (8-18)mc • The surface temperature in the case of constant surface heatflux can be determined fromq( )sq s= h Ts −Tm → Ts = Tm+ (8-19)hh p
Page 1: Chapter 8:Internal Forced Convectio
Page 4 and 5: Average Velocity• The value of th
Page 6 and 7: • For incompressible flow in a ci
Page 8 and 9: The Entrance Region• A fluid ente
Page 10 and 11: Thermal Entrance Region• Consider
Page 12 and 13: • Surface heat flux can be expres
Page 14 and 15: Entry Lengths ()- HydrodynamicLamin
Page 18 and 19: • In the fully developed region,
Page 20 and 21: Constant Surface Temperature• The
Page 22 and 23: • The temperature difference betw
Page 24 and 25: Laminar Flow in TubesAssumptions:
Page 26 and 27: • Taking the limit as dr, dx 0 g
Page 28 and 29: • Combining the last two equation
Page 30 and 31: • A pressure drop due to viscous
Page 32 and 33: • Or∂T1 ∂Qu =−( )∂ x ρc
Page 34 and 35: • Separating the variables and in
Page 36 and 37: Constant Surface temperature (circu
Page 38 and 39: - HydrodynamicLaminar flowLh,lamina
Page 40 and 41: Turbulent flow in Tubes• Most cor
Page 42: Moody Diagram

Chapter 8: Internal Forced Convection

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