HEAT TRANSFER CHAPTER 6 Introduction to convection 们au Heat Transfer Su Yongkang School of Mechanical Engineering
Heat Transfer Su Yongkang School of Mechanical Engineering # 1 HEAT TRANSFER CHAPTER 6 Introduction to convection
CH6- INTRODUCTION Where we’ ve been. Basic conduction Heat Transfer inished Fourier’slaw: k kvt Where we’ re going: Begin study of convective heat transfer Newtons law of cooling =h( T-T Heat Transfer Su Yongkang School of Mechanical Engineering
Heat Transfer Su Yongkang School of Mechanical Engineering # 2 CH6 – INTRODUCTION Where we’ve been …… Basic Conduction Heat Transfer Finished Fourier’s law: Where we’re going: Begin study of convective heat transfer. Newton’s law of cooling: dx dt q = −k q = −kt ( ) = − q h Ts T
Convective transfer problem A FAMILY CIRCUS 2-6 201 Eh ty Krg mures siN. "I forget Does holding the door open let the cold air in, or the warm out? Heat Transfer Su Yongkang School of Mechanical Engineering
Heat Transfer Su Yongkang School of Mechanical Engineering # 3 Convective transfer problem
CH6 INTRODUCTION KEY POINTS THIS CHAPTER What are the key variables when analyzing convection heat transfer? Review boundary layer concept and significance Generalidea of relationship between velocity and thermal profiles in a boundary layer. Effect oflaminar versus turbulent flow on heat transfer potential Boundary layer similarity This chapter will be taught in two lectures: the firstincludes text book sections $6. 1 to 6.4 the other includes text book sections 86.5 to 6.10 Heat Transfer Su Yongkang School of Mechanical Engineering
Heat Transfer Su Yongkang School of Mechanical Engineering # 4 CH6 INTRODUCTION KEY POINTSTHIS CHAPTER • What are the key variables when analyzing convection heat transfer? • Review boundary layer concept and significance • General idea of relationship between velocity and thermal profiles in a boundary layer. • Effect of laminar versus turbulent flow on heat transfer potential • Boundary layer similarity • This chapter will be taught in two lectures: the first includes text book sections §6.1 to 6.4 the other includes text book sections §6.5 to 6.10
Convection overview Consider a flat plate oflength L, in air flow with velocity uoo and temperature Too y uoo, Too 1,7 Local heat flux is where h is the q"=H(T-7) local heat transfercoefficient Total heat transfer rate. ∫ql4=(,-T)hll q=hA(T-T average heat transfer coefficient Determination ofh'will rely on analytical as well as empirical data Heat Transfer Su Yongkang School of Mechanical Engineering
Heat Transfer Su Yongkang School of Mechanical Engineering # 5 Convection overview • Consider a flat plate of length L, in air flow with velocity u and temperature T • Local heat flux is: where h is the local heat transfer coefficient • Total heat transfer rate: h = average heat transfer coefficient Determination of ‘h’ will rely on analytical as well as empirical data ( ) = − q h Ts T = = − s As s s A q q dAs (T T ) hdA ( ) q = hAs Ts −T