Problems with HTC

NCMV · March 2, 2010, 02:44

Hi. I´m doing my master thesis in heat transfer. I´ve simulated a simple pipe, flowing liquid water both inside and outside. Flow is turbulent. In the post i see results trought a contour and variation of temperatures appear, but when i apply probe option the calculated values are differents in comparison to legend values. And the HTC values are higher. I´m new in CFX, i´m very confuse.

Regards.

P.D.: excuse me for my English, i´m learning it.

ghorrocks · March 2, 2010, 17:57

What is your question? I think you are asking two questions:
1) Why are the probed temperatures different to the contours?
2) Why are the HTC values different between contours and probes?

Assuming these are your questions:
Be aware that the probe function in CFD-Post interpolates between adjacent nodes. This can lead to differences between the probed value and the contour value. Also the HTC only exists at the wall and is zero elsewhere. This means if your probe point is off the wall it will interpolate between the wall value and zero in the interior.

NCMV · March 2, 2010, 21:49

Hi Glenn. Thanks for your help. I didn´t know about probe function interpolation. now i understand why the vaues are differents. I need to know about de HTC value at pipe anular area and somebody told me that i should use the function calculator and apply ave option but i don´t be sure. Could you explain me better about tha HTC exists only at the wall?

Regards.

ghorrocks · March 3, 2010, 06:43

It is only meaningful to do area operations on HTC where the area is a wall. That is averaging, integration etc over a wall boundary. HTC only exists at the walls.

NCMV · March 4, 2010, 02:42

Hi Glenn. And if i want to know about a fluid HTC, how could i do? It should be a fluid on near wall?

Grettings.

ghorrocks · March 4, 2010, 06:47

I don't think you understand. Wall HTC only exists at the walls. It does not exist in the flow. You must be talking about some other HTC for the interior of the flow - maybe multiphase?

March 2, 2010, 02:44	Problems with HTC	#1
NCMV New Member Norkely Marcano Join Date: Mar 2010 Posts: 4 Rep Power: 16	Hi. I´m doing my master thesis in heat transfer. I´ve simulated a simple pipe, flowing liquid water both inside and outside. Flow is turbulent. In the post i see results trought a contour and variation of temperatures appear, but when i apply probe option the calculated values are differents in comparison to legend values. And the HTC values are higher. I´m new in CFX, i´m very confuse. Regards. P.D.: excuse me for my English, i´m learning it.

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March 2, 2010, 17:57		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	What is your question? I think you are asking two questions: 1) Why are the probed temperatures different to the contours? 2) Why are the HTC values different between contours and probes? Assuming these are your questions: Be aware that the probe function in CFD-Post interpolates between adjacent nodes. This can lead to differences between the probed value and the contour value. Also the HTC only exists at the wall and is zero elsewhere. This means if your probe point is off the wall it will interpolate between the wall value and zero in the interior.

March 2, 2010, 21:49		#3
NCMV New Member Norkely Marcano Join Date: Mar 2010 Posts: 4 Rep Power: 16	Hi Glenn. Thanks for your help. I didn´t know about probe function interpolation. now i understand why the vaues are differents. I need to know about de HTC value at pipe anular area and somebody told me that i should use the function calculator and apply ave option but i don´t be sure. Could you explain me better about tha HTC exists only at the wall? Regards.

March 3, 2010, 06:43		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	It is only meaningful to do area operations on HTC where the area is a wall. That is averaging, integration etc over a wall boundary. HTC only exists at the walls.

March 4, 2010, 02:42		#5
NCMV New Member Norkely Marcano Join Date: Mar 2010 Posts: 4 Rep Power: 16	Hi Glenn. And if i want to know about a fluid HTC, how could i do? It should be a fluid on near wall? Grettings.

March 4, 2010, 06:47		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	I don't think you understand. Wall HTC only exists at the walls. It does not exist in the flow. You must be talking about some other HTC for the interior of the flow - maybe multiphase?