Heat flux Boundary condition
 

Hi Guys,
I am trying to model a Helical heat exhanger embedded in the soil. Hot water flows in form the top of the helical pipe, circulates to the bottom, losing heat to the soil and the travels up a central straight pipe as shown in the schematic.
Needless to say the water at the outlet is cooler than the hot inlet water.
The top, bottom and curved surface of the cylinder soil shown is at a fixed temperature.
I need the soil temperature distribution if a fixed amount of heat is rejected to the soil by the pipe (say 1000 Watts total). The challenge is the heat flux is not constant.
Is there a way (Pehaps a UDF?) that tells Fluent that the integral of heat flux and pipe are is 1000 Watts, which would then allow the Fluent to calculate the inlet and outlet temperatures needed to transfer this heat as well as the soil temperature distribution.
Has anyone solved a similar Boundary condition. If yes, help a buddy out.
Stay awesome guys. :cool:

Can someone please help :-(

This is not a valid BC because it is under-defined. There are infinite heat flux distributions that can give you an integral of 1000 W.

Can you use a uniform heat flux boundary condition? You have to do the basic algebra to figure out what heat flux gives 1000 W (divide 1000 W by the surface area).

Once you decide that you want a particular heat flux boundary condition, your problem is decoupled. You can no longer solve the problem of a pipe + soil together. You must solve the soil by itself with the heat flux boundary condition or the pipe by itself with the heat flux boundary condition.