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 Marie13 February 18, 2013 13:14

Convection in a hot water tank

Hi,

I am working on a simplified 2D transient model of a hot water tank. I am using a k-epsilion turbulence model. I have activated buoyancy and gravity and am using the Boussinesq model for density.For boundary conditions I have made the walls adiabatic and fixed the temperature of the heating coil. The water does heat up but it seems like it is only by pure conduction as I am not getting any velocity in the tank. Could someone please help me out?

Thank you.

 delaneyluke February 19, 2013 16:27

Seems like natural convection, you would have to run an unsteady case in order to capture effects of natural convection.

Regards
Luke

 Marie13 February 19, 2013 16:58

Thanks Luke. But I did run an unsteady model.

I think it may have to something to do with the density model. The water heats up from 15C to about 80C, which might be the reason for the Boussinesq not to work. I ran the model using the perfect gas density model and this gave me better results; however, I don't think it is right to use that for water.

 delaneyluke February 19, 2013 17:05

Another point, which I missed earlier.
Your presumption that low water velocity implies conduction could be wrong. Since natural convection is generally a low velocity phenomenon, higher velocities would imply a forced convection.
So convection would be your primary mode of heat transfer even though velocities are low in your domain.

Regards
Luke

 MARIO276 February 19, 2013 17:45