Chapter 8: Internal Forced Convection

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• Separating the variables and integrating twiceq4s 2T = ⎜r − Cr2 ⎟+ 1+ C2kR• Boundary conditions⎛⎝r4R⎞⎠(8-56)– Symmetry at r = 0:∂ T r =0( )∂r=0C 1 =0–At r = R:T(r=R) = T sC 2T2 4qR ⎛s3 r r= Ts− ⎜ − +k ⎝4 R 4R2 4⎞⎟⎠(8-57)
• Substituting the velocity and temperature profile relations (Eqs.8–41 and 8–57) into Eq. 8–4 and performing the integrationTmpm= 流度 = =1124qR s(8-58) Tm= Ts−( )s s mk24 48h = k = k = 4.36k11 R 11 D DConstant heat flux (circular tube, laminar)Nu=V∫avgcT r2R2R0( ) δ mp ( ) ρ ( )( ) ( )hD= = 4.36 = 數k∫AccT r u r 2πrdr(2π )mc ρV R c∫p avg pT r u r rdrq≡ h T −T(8-4)(8-59)(8-60)
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 16 and 17: General Thermal Analysis• In the
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 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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