Chapter_6_Part_A__Notes

# Chapter_6_Part_A__Notes - Introduction to Convection...

This preview shows pages 1–7. Sign up to view the full content.

Introduction to Convection: Introduction to Convection: Flow and Thermal Considerations Flow and Thermal Considerations Chapter Six and Appendix E Chapter Six and Appendix E Sections 6.1 to 6.9 and E.1 to E.3 Sections 6.1 to 6.9 and E.1 to E.3

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Boundary Layer Features Boundary Layer Features Boundary Layers: Physical Features Velocity Boundary Layer A consequence of viscous effects associated with relative motion between a fluid and a surface. A region of the flow characterized by shear stresses and velocity gradients. A region between the surface and the free stream whose thickness increases in the flow direction. δ Why does increase in the flow direction? ( ) 0.99 uy u →= 0 s y u y τ µ = = Manifested by a surface shear stress that provides a drag force, . s D F s D ss A F dA = How does vary in the flow direction? Why? s
Boundary Layer Features (cont.) Boundary Layer Features (cont.) Thermal Boundary Layer A consequence of heat transfer between the surface and fluid. A region of the flow characterized by temperature gradients and heat fluxes. ( ) 0.99 s t s TT y δ →= A region between the surface and the free stream whose thickness increases in the flow direction. t 0 s fy T qk y = ′′ =− Why does increase in the flow direction? t Manifested by a surface heat flux and a convection heat transfer coefficient h . s q 0 / s kT y h = −∂ ∂ If is constant, how do and h vary in the flow direction? () s s q

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Local and Average Coefficients Local and Average Coefficients Distinction between Local and Average Heat Transfer Coefficients Local Heat Flux and Coefficient : () s qh TT ′′ =− Average Heat Flux and Coefficient for a Uniform Surface Temperature : ss ATT s s A qq d A = s s s A T T hdA 1 s s A s h hdA A = •Fo r a flat plate in parallel flow : 1 L o hh d x L =
Boundary Layer Equations Boundary Layer Equations The Boundary Layer Equations • Consider concurrent velocity and thermal boundary layer development for steady, two-dimensional, incompressible flow with constant fluid properties and negligible body forces . ( ) , , p ck µ • Apply conservation of mass , Newton’s 2 nd Law of Motion and conservation of energy to a differential control volume and invoke the boundary layer approximations . Velocity Boundary Layer : ,, uv uu v v yx y x ∂∂ ± ± Thermal Boundary Layer : TT ±

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Boundary Layer Equations (cont.) Boundary Layer Equations (cont.) Conservation of Mass : 0 uv xy ∂∂ += In the context of flow through a differential control volume, what is the physical significance of the foregoing terms, if each is multiplied by the mass density of the fluid?
This is the end of the preview. Sign up to access the rest of the document.

### Page1 / 20

Chapter_6_Part_A__Notes - Introduction to Convection...

This preview shows document pages 1 - 7. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online