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-   -   HTC: How to choose reference temperature value (http://www.cfd-online.com/Forums/star-ccm/97846-htc-how-choose-reference-temperature-value.html)

halcyon February 27, 2012 08:26

HTC: How to choose reference temperature value
 
Hi,
I am doing a simulation (laminar,steady) to predict the HTC between a solid body (23C) and air (20C).
I thought that the temperature reference value you can choose in the HTC field function should be somehow related to the air temperature in my case.
But if I choose the T_ref 20C I get an HTC interval of [-1.5,18]. If I choose T_ref 18C the HTC look much better within an interval of [-0.5,5].

Is there any rule how to choose this value and is it OK to use that value that makes the simulation more realistic?
For me such a "playing around" method doesn't seem to be very professional...

misagh April 12, 2012 06:07

reference value
 
i have the same problem.
i dont know which tem. to choose for ref. value.
a tube entering water @300 exiting @302
it is so sensitive to tempreture value.
any help is appreciated.

RobertB April 12, 2012 08:19

Typically HTCs are referred to the bulk entrance gas temperature, as it is easy to measure experimentally.

If you have very low T rises then it is not surprising that your HTC will move around significantly as the dT is very small.

You will need to use variable fluid properties and an appropriate grid. You also need to make sure that your model is set up exactly the same as the experiment it is trying to reproduce.

misagh April 12, 2012 11:46

yes.you are right.when i choose enterace tempreture the diagrams trend is like that of the experimental diagram,but with significant error./exp. digram is available/
thats because of mesh unaccuracy.
any way,thank you Robert.


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