HEAT TRANSFER chAPTER 8 Internal flow 们au Heat Transfer 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 regio Boundary layer region (r,x) Hydrodynamic entrance region Fully developed region Where we’ re going Developing heat transfer coefficient relationships and correlations for internal flow Heat Transfer 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 correlationsfor 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 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 4.36 k for constant surface temperature hD 3.66T=C k Note: the thermal conductivity k should be evaluated at T' Heat Transfer 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 ·2. The entry region for the constant surface temperature condition D 0.0668RepP D Nun=3.66+ 2/3 1+0.04 Ren pr thermal entry length -Thermal e Combined entry lensth Constant surface Pr=0.7) heat flua Entrance terion Fuly developed region 10 4.36 Constant srface temperature 0001 0005001 0050.1 0.5 G Heat Transfer 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