Thermal__convection coefficient

[05735620d]

I would like to ask how to define the convection coefficient?


I read many books which mention some complicated formular.

Can you give some example of convection coefficient?


For example: what is the convection coefficient in normal condition(no wind)?


what is the convection coefficint when some blowed wind?

Hope you can solve my problem!!!

 

[Miko]

Hi Chan ....and welcome on the forum.


As I know you can use Pro/MECHANICA for Thermal analysis. Or just use other program for doingsometing like that. Maybe FLUENT or ANSYS.


Good luck.
Edited by: Miko

 

[mohit_gupta]

HI


thermal convection is a mode of heat transfer wherein there is interaction between two different media. for example air blowing over a hotplate. there can be no convection if there is no fluid media i.e no convection in vacuum. so we cannot have a convection coefficient when no wind. but as far as I decipher your message you are talking about still air and blowing air.


the coefficient are basically governed by reynolds number which differentiates between the fluids velocity..i.e its a number which denotes whether a fluid is turbulent or laminar...and there is no thumb rule which can be used for convection coefficient values. the formulas have to be applied according to the condition prevailing in your problem...i suggest use a heat and mass transfer handbook or Heat and mass transfer by Incropera for this....


u could assume 5-20 W/m^2 K for laminar (still) air over a heated plate...but for turbulent air u will have determine the values. though assuming the values will result a vague answer.