HEAT TRANSFER CHAPTER 8 Internal flow Heat Transfer #1 Su Yongkang School of Mechanical Engineering
Heat Transfer Su Yongkang School of Mechanical Engineering # 1 HEAT TRANSFER CHAPTER 8 Internal flow
Internal Flow Heat Transfer Where we've been ..... Introduction to internal flow,basic concepts, energy balance. Inviscid flow region Boundary layer region u(r.x) Hydrodynamic entrance region Fully developed regior xd. Where we're going: Developing heat transfer coefficient relationships and correlations for internal flow Heat Transfer #2 Su Yongkang School of Mechanical Engineering
Heat Transfer Su Yongkang School of Mechanical Engineering # 2 Internal Flow Heat Transfer Where we’ve been …… • Introduction to internal flow, basic concepts, energy balance. Where we’re going: • Developing heat transfer coefficient relationships and correlations for internal flow ro
Internal Flow Heat Transfer KEY POINTS THIS LECTURE Convection correlations Laminar flow Turbulent flow Other topics Non-circular flow channels Concentric tube annulus Heat Transfer #3 Su Yongkang School of Mechanical Engineering
Heat Transfer Su Yongkang School of Mechanical Engineering # 3 Internal Flow Heat Transfer KEY POINTS THIS LECTURE • Convection correlations – Laminar flow – Turbulent flow • Other topics – Non-circular flow channels – Concentric tube annulus
Convection correlations:laminar flow in circular tubes 1.The fully developed region from the energy equation,we can obtain the exact solution. for constant surface heat flux hD Nup= =4.36 q"=C k for constant surface temperature hD Nup= k =3.66 T、=C Note:the thermal conductivity k should be evaluated at T Heat Transfer #4 Su Yongkang School of Mechanical Engineering
Heat Transfer Su Yongkang School of Mechanical Engineering # 4 Convection correlations: laminar flow in circular tubes • 1. The fully developed region from the energy equation,we can obtain the exact solution. for constant surface heat flux for constant surface temperature Note: the thermal conductivity k should be evaluated at . 4.36 k hD NuD q s C 3.66 k hD NuD Ts C Tm
Convection correlations:laminar flow in circular tubes 0 2.The entry region for the constant surface temperature condition Rep Pr Wup=3.66+ 72/3 人1 1+-0.04Rep Pr thermal entry length ----Thermal entry length Combined entry length Constant sorface (Prs0.7) heat flux 20 Entrance region Fulty developed region 10 4.36 Constant surface 3.66 temperature 2 0.001 0.c050.01 0.0501 0.5 Heat Transfer #5 Su Yongkang School of Mechanical Engineering
Heat Transfer Su Yongkang School of Mechanical Engineering # 5 Convection correlations: laminar flow in circular tubes • 2. The entry region for the constant surface temperature condition thermal entry length 2/3 Re Pr L D 1 0.04 Re Pr L D 0.0668 3.66 D D NuD