HEAT TRANSFER Final review 们au Heat Transfer Su Yongkang School of Mechanical Engineering
Heat Transfer Su Yongkang School of Mechanical Engineering # 1 HEAT TRANSFER Final Review
Final review session 50 TED HAS BEEN BASED ON YOUR S0METIMES THERES A TRAINING YOU FOR WORK, ID SAY HE S FINE LINE BE TWEEN THE PAST SIX MONTHS. EI PLAYING THE WORLDS E CRIMINALLY ABUSIVE ONGEST PRACTICAL BEHAVIOR AND FUN JOKE ON YOU Copyright 9 2003 Uni ted Feature Syndicate, Inc Heat Transfer Su Yongkang School of Mechanical Engineering
Heat Transfer Su Yongkang School of Mechanical Engineering # 2 Final Review Session
Viscous flow The Navier-Stokes Equations Nonlinear, second order, partial differential equations au auau au a-u auau +l+y-+ +pgx+u at a a-y ay ay +ng1+1 at a ay az ax ay az a21a21 +g:+p O au ay a 0 ox ay a Couette flow. Poiseuille flow Heat Transfer Su Yongkang School of Mechanical Engineering
Heat Transfer Su Yongkang School of Mechanical Engineering # 3 Viscous Flow • The Navier-Stokes Equations Nonlinear, second order, partial differential equations. • Couette Flow, Poiseuille Flow. + + + + = − + + + + + + + = − + + + + + + + = − + + + 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 z w y w x w g z p z w w y w v x w u t w z v y v x v g y p z v w y v v x v u t v z u y u x u g x p z u w y u v x u u t u z y x = 0 + + z w y v x u
Convection Basic heat transfer equation q=h As(TS-Too)h= average heat transfer coefficient Primary issue is in getting convective heat transfer coefficient h ∫ hda. or, for unit width:h=r∫h A L 0 h relates to the conduction into the fluid at the y 0 Heat Transfer Su Yongkang School of Mechanical Engineering
Heat Transfer Su Yongkang School of Mechanical Engineering # 4 Convection • Basic heat transfer equation • Primary issue is in getting convective heat transfer coefficient, h • h relates to the conduction into the fluid at the wall q = h A (T −T ) s s h = average heat transfer coefficient = = L A s s h dx L h dA h A h s 0 1 or,for unit width: 1 ( ) = − = T T y T k h s y f x 0 -
Convection Heat Transfer Correlations Key is to fully understand the type of problem and then make sure you apply the appropriate convective heat transfer coefficient correlation External flow For laminar flow over flat plate dP 0 ao 2 X nu 0.332Re . 2D- Nur k 0.66 4Rel2 pr X For mixed laminar and turbulent flow over flat plate h hamdx +hurd 0 uL 0037Re4871/P3 0.6<Pr<60 5×10·<Rer<10 Xc=5×105 Fq.7.41 Heat Transfer Su Yongkang School of Mechanical Engineering
Heat Transfer Su Yongkang School of Mechanical Engineering # 5 Convection Heat Transfer Correlations • Key is to fully understand the type of problem and then make sure you apply the appropriate convective heat transfer coefficient correlation External Flow For laminar flow over flat plate For mixed laminar and turbulent flow over flat plate = 0 dx dP T ,U Ts y 3 1 2 1 = 0.332Rex Pr k h x Nu x x 3 1 2 1 = 0.664Rex Pr k h x Nu x x = + L xc turb xc x hlamdx h dx L h 1 0 ( ) Eq. 7.41 5 10 Re 10 Re 5 10 0.6 Pr 60 0.037 Re 871 Pr 5 x,c 5 8 4 5 1 3 L = = − L NuL