Lecture 10 Transient conduction

Lecture 10 Transient conduction - 1 MECE 4364 Heat Transfer...

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MECE 4364 Heat Transfer Prof. Dong Liu Department of Mechanical Engineering University of Houston 1 Lecture 10 – Sep 23, 2010 Lecture 10 Transient Conduction 2
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Lecture 10 Overview ± Transient conduction ± a heat transfer process in which the temperature varies with both time and location in a medium. ± initiated whenever a system experiences a change in operating conditions and proceeds until a new thermal equilibrium (steady state) is achieved. ± Typical changes in operating conditions: ± surface convection ± surface radiation ± surface temperature/heat flux ± internal energy generation ± Want to know ± Time dependence of temperature distribution within the solid ± Heat transfer between the solid and its surrounding h , T h r , T sur 3 () p TT T T ck T k k k tx x y y z z ∂∂ ρ ∂∂ ∂∂ ⎛⎛ =∇⋅ ∇ = + + ⎜⎟ ⎝⎝ Lecture 10 Transient Conduction ± How to calculate the temperature evolution of the solid? ± Transient, multidimensional problem – difficult to solve directly ± The lumped capacitance approach assumes ± Temperature distribution is spatially uniform throughout the transient process: the temperature throughout the solid has no spatial variation at any given time instant ± In another word, temperature gradients within the solid are negligible ± Caution: heat conduction without temperature gradient implies infinite thermal conductivity – closely approximated if 4 Metal forging ± Initially at uniform temperature T i ± Immersing it in a liquid of T < T i ±
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This note was uploaded on 01/27/2011 for the course MECE 4364 taught by Professor Lipinglui during the Winter '10 term at University of Houston.

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Lecture 10 Transient conduction - 1 MECE 4364 Heat Transfer...

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