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siw October 2, 2013 09:48

Interface heat or temperature increase
 
Hi,

I'm modelling an airflow through a system and part of this includes the air flowing through a heater (e.g. a car radiator geometry but heats the air rather than cools). The heater geometry is too complex to model explicitly as it is made up of many small hot water pipes and fins which imparts heat to the airflow. The goemetry also causes a pressure drop, much like a porous domain.

I don't have a flow rate vs pressure drop curve for the heater so I cannot determine the coefficients needed for a porous domain. Instead I thought to use an interface with an interface model with a negative pressure change to account for the pressure drop without having to include any subdomain or geometry. Also I have the pressure drop value at the design flow rate for this.

But the only thermal data I have is the heat transfer coefficient and the design air heater inlet and outlet temperatures and I don't see where this can be used with the interface. I thought about using a subdomain just so that I can add an energy source but without a momentum source for the pressure drop, for reason explained above.

Are there any recommendations to model this addition of heat and pressure drop to the airflow?

Thanks.

singer1812 October 2, 2013 13:24

What is to recommend? You are hosed with the Pdrop, you need one more point without making some gross assumptions.

I assume you have only h and dT for only that one point also? You need a bit more information than that.

I suppose you could assume h=f(V^1/2). You can replace the 1/2 by whatever value you wish (tube in cross flow perhaps will give you that exponent vs Re, with values ranging from 0.3-0.8).


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