Fan heater model: what turbulence source to use?
 

Hi all,

(I originally posted this in the CFX forum on this site - however it is not a code specific question, so to reach a wider audience I am reposting here. Apologies for double posting rather than cross posting on this occasion.)

I'm modelling a mixed natural / forced convection problem, which is driven in part by a number of industrial electric fan heaters. The heaters are a very standard type of design, with a fan blowing air over electric elements. Power is ~9kW each, air throughput is ~1000 m^3/hour each (see http://www.tombling.com/heaters/portable-heaters.htm for a typical example of the type of heater).

I want to model in these as sources in my CFD model. I've included sources for the momentum and energy equations, which give me the correct heat input and air flow rate. However, I'm not 100% sure about how to calculate appropriate turbulence model sources. I'm using the SST turbulence model. I will perform a sensitivity analysis to the turbulence source terms, but I would really appreciate any help you can give in establishing a sensible "best guess" on which to base my model.

What recommendations / best practice guidelines would you suggest for modelling the turbulence generated by a fan heater? A percentage of the fan motor power perhaps as a KE source?

Many thanks for your replies. Andy

(PS: Experimental assessments will not be possible in this case.)