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-   -   Problems referencing to temperature (http://www.cfd-online.com/Forums/cfx/23218-problems-referencing-temperature.html)

andreas October 27, 2006 01:44

Problems referencing to temperature
 
Hello everyone,

I'm trying set up a model, that describes the heat transfer outside a tube, during film boiling. The heat transfer coefficient is described by a formula, that depends on the outter wall temperature of the tube. I'm using CEL to include the formula. When I try include the wall temperature by means of variable T, CFX returns the following message in the physics panel: "The varible 'T' referenced in parameter 'Heat Transfer Coefficient' does not have one of the required prefixes: phase or particle" I also tried to add the Prefix Steel.T ("Steel" is the name of my solid material) but the error message stays the same. Does anyone know what the problem is.

Thanks in advance.

Andreas


Robin October 27, 2006 09:05

Re: Problems referencing to temperature
 
Where are you using this expression?

andreas October 27, 2006 09:45

Re: Problems referencing to temperature
 
I have one fluid and one solid domain. The fluid inside the tube and the tube wall itselve. The fluid outside the tube is not concidered. I use the "tbulk for htc" expert parameter to force a bulk temperature instead. I'm trying to calculate the Heatflux by means of the heat transfer coefficien alpha=f(T) on the outter tube wall. The Value of Heatflux should be give to the Heat Transfer>Heat Flux Option of the outter wall boundary condition (solid domain). When I change my solid domain to fluid domain the variable T is accessible. But with a solid domain CFX asks for a prefix phase or particle.

Do you have any idea why the error message occures?

Robin October 27, 2006 10:02

Re: Problems referencing to temperature
 
Hi Andreas,

First of all, the "tbulk for htc" parameter only affects the calculation of the heat transfer coefficient variable for output to the res file. It does not affect your boundary condition.

Heat Transfer Coefficient is available as a boundary condition on exterial walls. Why aren't you using this?

Regards, Robin

andreas October 27, 2006 10:24

Re: Problems referencing to temperature
 
Hello Robin,

I also tried Heat Transfer Coefficient. In both cases CFX was not able to access the wall temperature, which is necessary to calculate my temperature dependant Expression: alpha representing the HTC during film boiling.

Robin October 27, 2006 10:49

Re: Problems referencing to temperature
 
Are you applying this at the interface or the outer wall?

andreas October 30, 2006 00:01

Re: Problems referencing to temperature
 
I'm applying it at the outer wall. And as I mentioned I can access the variable T when I change my solid domain to fluid domain. So I would assume, it has something to do with the availability of temperature variables in solid material.

andreas October 30, 2006 07:26

CFX 10.0 Bug
 
Obviously the occoring error message was caused by a bug in CFX 10.0. The bug is listed as one 25 issues that can be fixed by an addtitional service pack.


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