topic is it necessary to specify gravity vector for natural convection? in CFD Forum

is it necessary to specify gravity vector for natural convection?

Anonymous — Sat, 11 Nov 2017 12:33:58 GMT

Hi,

I am modelling a phase change simulation in refrigerator condenser for refrigerant r134a. This is natural convection. everything seems ok, but I am afraid because I have not specified any gravity vector.

but is it necessary to specify gravity vector? what will be the effect of it?

fluid flow and heat transfer is on. quality is changing.

regards,

Akshay Kumar

Re: is it necessary to specify gravity vector for natural convection?

Jon.Wilde — Sat, 11 Nov 2017 13:15:28 GMT

If the flow is slow enough for the difference in density due to temperature to effect the flow, then yes you should have it on. Otherwise you have no natural convection.

With refrigerant, I would suspect that this is not the case though and you could disregard any natural convection.

You would need large variations and an incredibly low flow rate for it to have any effect.

Does that answer your question?

Re: is it necessary to specify gravity vector for natural convection?

Anonymous — Sat, 11 Nov 2017 14:02:58 GMT

Thank you sir @Jon.Wilde

regards,

Akshay Kumar