lecture 21 - Thermal and Fluids Engineering I Lecture 21...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
Thermal and Fluids Engineering I Lecture 21 Page 1 Lecture 21 – Forced Convection in External Flow Forced Convection – Fluid is moved by mechanical means: Natural Convection – Fluid is moved by buoyancy forces: In forced convection on a flat plate
Background image of page 1

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

View Full DocumentRight Arrow Icon
Thermal and Fluids Engineering I Lecture 21 Page 2 The development of the thermal boundary layer depends on Re and k – thermal conductivity c p – specific heat µ – viscosity More advanced analysis shows that the boundary layer depends on the Prandtl number: p c Pr k = Prandtl number Consider the thermal boundary layer () conv s f Qh A T T =− & where T f is fluid temperature and T s is surface temperature. cond s f T kA QT T δ & The ratio of convection to conduction is
Background image of page 2
Thermal and Fluids Engineering I Lecture 21 Page 3 () sf conv T cond T hA T T Q h kA Qk TT δ == & & Define the Nusselt number as char hL Nu k = Nusselt number Where L char is a characteristic length. For example, for convection in crossflow over a cylinder, the characterisitic length is the diameter.
Background image of page 3

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

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/08/2008 for the course ENGR 2250 taught by Professor Borca-tasciuc during the Spring '08 term at Rensselaer Polytechnic Institute.

Page1 / 7

lecture 21 - Thermal and Fluids Engineering I Lecture 21...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online