Mixed Flow Convection (3 separate domains)

mariconeagles96 · October 17, 2014, 03:27

Hi People! Hope you could help me out...

Im trying to check the thermal performance of my electronic enclosure in an automotive environment with ambient temp about 85C. This electronics enclosure is being attached to a metal plate which act as its heatsink. This metal plate is isolated and cooled by forced air convection using a blower. So basically I have 3 separate fluid domains. One is for my electronics enclosure (natural conv) and the other two is for my metal plate or "heatsink" and blower (forced convection). And since the blower have this given speed, then I should use here "rotating domain".

How do I setup the gravity orientation for this simulation since I could only setup in 2 directions only (+ and -) along the axis of rotation of the blower?

Thanks!

ghorrocks · October 17, 2014, 07:03

Depending on how much detail of the blower you need you might be able to use a momentum source rather than modelling the blower directly. To do this you will need the blower fan curve. It will be MUCH simpler and probably more accurate if you do this - but you will not be getting the detailed flow of the blower, just overall effect of it. Whether this is appropriate depends on details of your model.

If you have 2 air domains then it is usually bets to combine them into 1 domain covering both. Except if you have a rotating domain of course, then you have to put the rotating bit in a rotating frame of reference.

mariconeagles96 · October 17, 2014, 08:52

Thanks as always @ghorrocks. Actually im more interested on my electronic enclosure. Since this is a separate domain and not in contact with the blower flow domain, how can I set gravity on this since my options are only along the axis of rotation. Ive tried doing this but it seems that the flow via natural conv in the domain of the enclosure is not moving even there are already vent holes.

ghorrocks · October 18, 2014, 03:50

If you have significant natural convection then you have to consider carefully how to model the rotating domain. Many of the approaches (eg frozen rotor) will imply strange things which you probably don't want.

But based on your comment then it appears the momentum source approach will be more appropriate for you and that simplifies things immensely. You will not need to think about how to apply a gravity vector in a rotating domain for instance (because you do not have a rotating domain).

October 17, 2014, 03:27	Mixed Flow Convection (3 separate domains)	#1
mariconeagles96 Member Join Date: Jun 2011 Posts: 38 Rep Power: 15	Hi People! Hope you could help me out... Im trying to check the thermal performance of my electronic enclosure in an automotive environment with ambient temp about 85C. This electronics enclosure is being attached to a metal plate which act as its heatsink. This metal plate is isolated and cooled by forced air convection using a blower. So basically I have 3 separate fluid domains. One is for my electronics enclosure (natural conv) and the other two is for my metal plate or "heatsink" and blower (forced convection). And since the blower have this given speed, then I should use here "rotating domain". How do I setup the gravity orientation for this simulation since I could only setup in 2 directions only (+ and -) along the axis of rotation of the blower? Thanks!

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October 17, 2014, 07:03		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,852 Rep Power: 144	Depending on how much detail of the blower you need you might be able to use a momentum source rather than modelling the blower directly. To do this you will need the blower fan curve. It will be MUCH simpler and probably more accurate if you do this - but you will not be getting the detailed flow of the blower, just overall effect of it. Whether this is appropriate depends on details of your model. If you have 2 air domains then it is usually bets to combine them into 1 domain covering both. Except if you have a rotating domain of course, then you have to put the rotating bit in a rotating frame of reference.

October 17, 2014, 08:52		#3
mariconeagles96 Member Join Date: Jun 2011 Posts: 38 Rep Power: 15	Thanks as always @ghorrocks. Actually im more interested on my electronic enclosure. Since this is a separate domain and not in contact with the blower flow domain, how can I set gravity on this since my options are only along the axis of rotation. Ive tried doing this but it seems that the flow via natural conv in the domain of the enclosure is not moving even there are already vent holes.

October 18, 2014, 03:50		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,852 Rep Power: 144	If you have significant natural convection then you have to consider carefully how to model the rotating domain. Many of the approaches (eg frozen rotor) will imply strange things which you probably don't want. But based on your comment then it appears the momentum source approach will be more appropriate for you and that simplifies things immensely. You will not need to think about how to apply a gravity vector in a rotating domain for instance (because you do not have a rotating domain).