calculation of htc

christopher0 · April 6, 2010, 07:01

hello,
I performs calculations in CFX. One of my aims is to determine the heat transfer coefficient based on two steps. First step performs calculations using adiabatic wall boundary condition allows no heat transfer across the wall boundary. In second step (after convergence) I use isothermal wall with Ti=Ta-dT. Ta -gas temperature at adiabatic walls; Ti -gas temperature at isothermal walls; dT -temperature difference, for example 150K. These calculations allow to get wall heat flux (q) and then the heat transfer coefficient can be determined from the formula: htc=q/dT. I have problem with finding information about this method. Can you give some references describing this method?

dvolkind · April 6, 2010, 12:41

Hello!

I don't really get what You are trying to do with adiabatic wall boundary. Are You modelling both fluid and solid domains?
Anyway, to calculate HTC properly You need to apply temperature BC to the wall You are interested in. Then, in CFX-Post divide the average heat flux by [T(wall)-T(fluid)]. Heat flux is calculated via Function Calculator - > AreaAve (heat flux)@wall. The choice of T(fluid) depends on the problem.

ztdep · April 7, 2010, 00:53

Dear friends:
Since the wall is adiabatic, that means the heat flux is zero.
am i right?

dvolkind · April 7, 2010, 03:09

"Quote: Since the wall is adiabatic, that means the heat flux is zero.
am i right?"
Yes, You are right.

April 6, 2010, 07:01	calculation of htc	#1
christopher0 New Member Join Date: Apr 2010 Posts: 1 Rep Power: 0	hello, I performs calculations in CFX. One of my aims is to determine the heat transfer coefficient based on two steps. First step performs calculations using adiabatic wall boundary condition allows no heat transfer across the wall boundary. In second step (after convergence) I use isothermal wall with Ti=Ta-dT. Ta -gas temperature at adiabatic walls; Ti -gas temperature at isothermal walls; dT -temperature difference, for example 150K. These calculations allow to get wall heat flux (q) and then the heat transfer coefficient can be determined from the formula: htc=q/dT. I have problem with finding information about this method. Can you give some references describing this method?

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April 6, 2010, 12:41		#2
dvolkind Member Dmitry Volkind Join Date: Jan 2010 Location: Ekaterinburg, Russia Posts: 64 Rep Power: 16	Hello! I don't really get what You are trying to do with adiabatic wall boundary. Are You modelling both fluid and solid domains? Anyway, to calculate HTC properly You need to apply temperature BC to the wall You are interested in. Then, in CFX-Post divide the average heat flux by [T(wall)-T(fluid)]. Heat flux is calculated via Function Calculator - > AreaAve (heat flux)@wall. The choice of T(fluid) depends on the problem.

April 7, 2010, 00:53		#3
ztdep Senior Member p ding Join Date: Mar 2009 Posts: 427 Rep Power: 19	Dear friends: Since the wall is adiabatic, that means the heat flux is zero. am i right?

April 7, 2010, 03:09		#4
dvolkind Member Dmitry Volkind Join Date: Jan 2010 Location: Ekaterinburg, Russia Posts: 64 Rep Power: 16	"Quote: Since the wall is adiabatic, that means the heat flux is zero. am i right?" Yes, You are right.