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-   -   veriable heatWallFlux / heat loss (https://www.cfd-online.com/Forums/openfoam/78223-veriable-heatwallflux-heat-loss.html)

 Shoonya July 15, 2010 10:54

veriable heatWallFlux / heat loss

Hello All,
I have vertical annulus cylinder with Argon gas filled in. The bottom of the annuli of the cylinder is kept at a constant temperature 400K. The outerSideWall is cooled by air having temperature of 393K. As the argon gas gets heated, it raises up; meanwhile it looses it energy along vertical direction. I have a problem the temperature BC I use at the outerSideWall of this vertical annulus. I can not use BC like wallHeatFlux becasue it gives constant heat flux. The gas is loosing energy due to cooling at the outerSideWall, so it will have variable type of heat flux along vertical direction. I need assistance that how this variable heat transfer could be implemented. Though I have tried with groovyBC as below

outerSideWall
{
type groovyBC;
value uniform 393;
valueExpression "T";

fractionExpression "0.5";
variables "hcof=0.04;Cp0=520;rho0=0.81;alphaEff=pow(10,-4);heatFlux=hcof *(T-Tamb);gradT=-heatFlux/(alphaEff * Cp0 * rho0);"
// valueExpression "";
timelines (
);

}

but this puts a constant heat loss at the outerSideWall. As gas raises up it will loss heat flux gradually rather then a fixed value. I need to incorporate this decrease of heat loss at the outerSideWall. I am thinking to make Tamb (temperature of argon) be variable such that it would be connected with the temperature of the internal field. If argon losses heat and temperature; that in turn decrease Tamb, henceforth the heatflux.
Could anybody help me in this problem; I would be really thankful to him. This might solve my long waited problem.
I have searched in the forums and find one link http://www.cfd-online.com/Forums/ope...ification.html has some short of similarity but I am unable to get the how exactly the code could be implemented.

thank you

dinesh

 Shoonya July 16, 2010 18:10

nonuniform list of scalar values allocation over the cells in curved surfaces

please somebody give me some clue for my previous problem.....meanwhile I have one more question; if I have a non uniform list of scalar fields like temperature gradients, then how does it referred over the cells on the curved boundary. I mean in case of 1-d boundary, 1st value of the list referes to 1st cell, 2nd value of the list referes to 2nd cell. But for 2-d or curved surface there are 2 directions, and we have single list then how this non-uniform list values are allocated over the cells.

thank you

regards

dinesh

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