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amit112amit May 1, 2013 10:58

Which is the best Solver for compressible real-gas internal flows
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I am looking at a three-dimensional analysis of a finned-tube gas cooled heat exchanger. I have attached a diagram to illustrate the geometry. I want to model solid pipe and attached flat-plate fins. A real gas (density varying with both pressure and temperature) is flowing inside the pipe. Air is blown over the pipe perpendicular to the length of pipe. Thus, air passes through the gap between fins. By forced convection, air will cool the fin and tube which are being heated by the hot real gas flowing inside the pipe, by conduction.

I tried using pressure-based solver of ANSYS Fluent 13.0's real gas model. But it has a serious limitation that all the fluids in the entire domain should be the same real gas. We cannot have a real gas and an ideal gas in the same setup. This is clearly written in documentation as a limitation of real-gas model. I have contacted customer support and they said that there is an update request for this feature which is being targeted for some future release. I tried writing my own UDFs to describe density as a function of pressure and temperature but I am not able to get the solution to converge.
I must use real gas model because the gas flowing inside the pipe has its density and other properties varying considerably with both pressure and temperature. If I use ideal gas assumption then density will depend only on temperature. Although the flow is compressible, it is not supersonic. Hence, I don't think I can use density-based solver. Also, density-based solver does not support shell-conduction model.
Can somebody suggest which is the best Software tool that I can use for this modelling? I have already used Fluent so kindly suggest something else which has specialty in handling real-gases and interaction with solids.

Amit Singh

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