Wall Heat Transfer Coefficient

sunilpatil · March 12, 2013, 09:00

Hello sir,
I want to write CEL Expression for wall heat transfer Coefficient to calculate
wall heat flux (Q) but in my problem wall is at middle of an encloser i want to calculate Q for both sides of wall how to specify particular surface to calculate
Wall Heat Flux (Q) in CFX.
Thank you sir.

JuPa · March 12, 2013, 09:46

Hi, post an image of your problem please.

If you're going to deduct wall heat transfer coefficient then I believe (one of the more experienced CFD engineers can correct me on this) you must have adequate refinement at the wall in order to resolve the thermal boundary layer, which is usually smaller than a viscous boundary layer!

sunilpatil · March 12, 2013, 11:17

Hello Sir,
Thank You for your Reply
I uploaded image (http://s8.postimage.org/vkixp5sxh/CFD.jpg)
i want to calculate heat transfer coefficient at wall side 1 and side 2 and also heat transfer rate if we subject wall for different temperature conditions or varying Temperature
Thank you sir.

JuPa · March 12, 2013, 12:45

Hi,

Please describe:
1. What your boundary conditions are.
2. Working fluid (water, air, or other).

It looks like a simple problem but without more thorough information I can't be of any help.

ghorrocks · March 12, 2013, 18:18

Are you simulating this as a conjugate heat transfer simulation? That is, including heat transfer in the wall?

sunilpatil · March 13, 2013, 07:44

Hello sir,
Thank you for your quick reply
i am simulating this as a conjugate heat transfer problem
Boundary conditions are
1.Varying Temperature With Time To middle Wall
2.Material Working Medium-air at 25 C , Wall = Copper
3.All other walls are adiabatic
Thank You

ghorrocks · March 13, 2013, 17:29

What do you mean by "varying temperature with time to middle wall".

sunilpatil · March 14, 2013, 01:24

Hello sir,
I am applying This(http://s23.postimage.org/plc9nhfcb/cfd.jpg) type boundary
condition to Middle Wall

In that
x-axis Time in Seconds
Y-axis Temperature in Kelvin
(all this for transient case)
Thank you sir

ghorrocks · March 14, 2013, 06:28

If you already know the temperature of the middle wall then why are you simulating the middle wall as a CHT solid? Just impose your temperature function as a temperature boundary and nothing else is required.

March 12, 2013, 09:00	Wall Heat Transfer Coefficient	#1
sunilpatil Senior Member sunil Join Date: Jul 2012 Location: Bangalore Posts: 179 Rep Power: 14	Hello sir, I want to write CEL Expression for wall heat transfer Coefficient to calculate wall heat flux (Q) but in my problem wall is at middle of an encloser i want to calculate Q for both sides of wall how to specify particular surface to calculate Wall Heat Flux (Q) in CFX. Thank you sir.

March 12, 2013, 11:17	Wall Heat Transfer Coefficient	#3
sunilpatil Senior Member sunil Join Date: Jul 2012 Location: Bangalore Posts: 179 Rep Power: 14	Hello Sir, Thank You for your Reply I uploaded image (http://s8.postimage.org/vkixp5sxh/CFD.jpg) i want to calculate heat transfer coefficient at wall side 1 and side 2 and also heat transfer rate if we subject wall for different temperature conditions or varying Temperature Thank you sir.

March 13, 2013, 07:44	Wall Heat Transfer Coefficient	#6
sunilpatil Senior Member sunil Join Date: Jul 2012 Location: Bangalore Posts: 179 Rep Power: 14	Hello sir, Thank you for your quick reply i am simulating this as a conjugate heat transfer problem Boundary conditions are 1.Varying Temperature With Time To middle Wall 2.Material Working Medium-air at 25 C , Wall = Copper 3.All other walls are adiabatic Thank You

March 14, 2013, 01:24	Varying Wall Temperature	#8
sunilpatil Senior Member sunil Join Date: Jul 2012 Location: Bangalore Posts: 179 Rep Power: 14	Hello sir, I am applying This(http://s23.postimage.org/plc9nhfcb/cfd.jpg) type boundary condition to Middle Wall In that x-axis Time in Seconds Y-axis Temperature in Kelvin (all this for transient case) Thank you sir

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March 12, 2013, 09:46		#2
JuPa Senior Member Mr CFD Join Date: Jun 2012 Location: Britain Posts: 361 Rep Power: 15	Hi, post an image of your problem please. If you're going to deduct wall heat transfer coefficient then I believe (one of the more experienced CFD engineers can correct me on this) you must have adequate refinement at the wall in order to resolve the thermal boundary layer, which is usually smaller than a viscous boundary layer!

March 12, 2013, 12:45		#4
JuPa Senior Member Mr CFD Join Date: Jun 2012 Location: Britain Posts: 361 Rep Power: 15	Hi, Please describe: 1. What your boundary conditions are. 2. Working fluid (water, air, or other). It looks like a simple problem but without more thorough information I can't be of any help.

March 12, 2013, 18:18		#5
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	Are you simulating this as a conjugate heat transfer simulation? That is, including heat transfer in the wall?

March 13, 2013, 17:29		#7
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	What do you mean by "varying temperature with time to middle wall".

March 14, 2013, 06:28		#9
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	If you already know the temperature of the middle wall then why are you simulating the middle wall as a CHT solid? Just impose your temperature function as a temperature boundary and nothing else is required.