[Mojtaba.a]

Hi all,
I am trying to simulate a simple pipe with constant heat flux walls, which are cooled by fluid flow going through the pipe.

Here is an image for better illustration:



Here is what I am gonna do. For wall BC I want to use:

dT/dn= (q-h*(T-T_inf))/(k_f)

In which T_inf is the average bulk temperature of the fluid, which varies across the pipe.

To calculate bulk temperature I want to use the average value of T as a variable of x (Length from the inlet).

How can I calculate this average in each x and use it as T_inf?

Is it possible to do this using groovyBC?

[gschaider]

Originally Posted by Mojtaba.a

Hi all,
I am trying to simulate a simple pipe with constant heat flux walls, which are cooled by fluid flow going through the pipe.

Here is an image for better illustration:



Here is what I am gonna do. For wall BC I want to use:

dT/dn= (q-h*(T-T_inf))/(k_f)

In which T_inf is the average bulk temperature of the fluid, which varies across the pipe.

To calculate bulk temperature I want to use the average value of T as a variable of x (Length from the inlet).

How can I calculate this average in each x and use it as T_inf?

Is it possible to do this using groovyBC?

Not the way you'd want to.

The first thing is that T_avg(s) is not really well defined after the pipe bend (BTW: convention is that x is a component of cartesian coordinates. The string length which you mean is s. At least the way I learned it). So the first thing would be to specify/calculate it for the whole geometry. Then you can calculate your T_avg(s) (for this there is actually a functionObject swakExpressionAverageDistribution in the development verson. But currently there is no way to feed that data back to your BC)

[Mojtaba.a]

Originally Posted by gschaider

Not the way you'd want to.

The first thing is that T_avg(s) is not really well defined after the pipe bend (BTW: convention is that x is a component of cartesian coordinates. The string length which you mean is s. At least the way I learned it). So the first thing would be to specify/calculate it for the whole geometry. Then you can calculate your T_avg(s) (for this there is actually a functionObject swakExpressionAverageDistribution in the development verson. But currently there is no way to feed that data back to your BC)

Thank you Bernhard.

[jherb]

Why don't you use the turbulentHeatFluxTemperature boundary condition?

See also http://www.cfd-online.com/Forums/ope...mperature.html

[gschaider]

Originally Posted by jherb

Why don't you use the turbulentHeatFluxTemperature boundary condition?

See also http://www.cfd-online.com/Forums/ope...mperature.html

In principle you're right. The problem is the T_inf he wants: an average of the T in the fluid. I don't think turbulentHeatFluxTemperature does that (last time I looked you specified the T_inf. It didn't get calculated from the solution)