Wall heating - through water pipes

[Radion]

Hello,
Me and my buddys doing aproject on Heat transfer.
we choose wall heating as our subject and we have some issue on modeling the system.

our system is :
two walls, one exposed to the atmosphere the other is the house wall.
between them there's a pipe with hot water and some aire.

we can't figured out how to approch the problem, we tried to model it with combination of convective and conduction butour DR said that the model is not good becouse there is an heat exchange.

any help will be appreciated.

thanks

 

[russ_watters]

Welcome to PF.

It isn't at all clear to me just what your setup is and what you are trying to model. Can you be more descriptive? Provide a diagram?

 

[256bits]

Hello,

we can't figured out how to approch the problem, we tried to model it with combination of convective and conduction butour DR said that the model is not good becouse there is an heat exchange.

thanks

Hello Radion,
Not all that easy of a problem. in an enclosed space.

Hot pipes will have heat flow to the air in the wall. With a convective component, the air will have a flow pattern within the space - maybe a loop of some sort. Maybe not, as the top of the air space may just become hotter than the bottom and convection will slow or stop at steady state - maybe. Depends upon the insulation of walls and the rate of heat flow through the walls.

If the hot water enters from the bottom, it loses heat and drops in temperature, so the water could have a negative temperature gradient from bottom to top. Heat flow temperature dependence would have more heat flow from the pipe bottom to the air, than heat flow from pipe top to air. Then again, is the air at the top warm enough to re-heat the water at the top...

The air in contact with the walls - conduction and maybe convection with reservations as stated previously.

An iterative process to find the heat flows, water and water temperatures, with respect to height in my opinion.
Similar to a heat exchanger analysis.