Domain size in Axial fans
Hi,
I was working on an axial fan geometry which is used for refrigeration and air conditioning equipment. I wanted to know as to what size of the domain should I keep so as to model the flow properly? Are there any standards of selecting domain sizes in case of Axial fans? 
Fluent published a short application brief (Ex 143) on a model of centrifugal fan using about 1/2 million cells back in 2001. This is easy to find on the internet and may provide you with some guidance.

Hi,
thanks for your reply alan. I went through the ex143 brief of Fluent but it does not state anything that describes the domain size that they had selected for the model. They have mainly elaborated on the MRF approach and the type of mesh used. 
I'm not sure what you mean by "domain size". I assumed that you meant the number of computational cells. If you mean the physical size of the domain (i.e. in meters), that will be determined by the size of the fan and what else needs to be included in the model.

Hi,
Yes, by domain size I mean the physical size of the domain. I meant like we have the standard practice of the domain size being 2D upstream and 3D downstream in case of Valves where D is the diameter of the valve. I was wondering if we follow any such practices in case of axial fans because the first time that I performed the simulation, I got bad results so I am thinking of increasing the domain size this time. 
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