Flow distribution in porous domain (CFX)

CFXer · July 28, 2020, 04:03

Hello

I am trying to simulate a heat exchanger as a porous media.(using CFX's porous domain)

So it has several channels that have flow non-uniformity.

I want to observe how the flow non-uniformity varies with the heat exchanger's header shape.

In my pre-test, the flow non-uniformity occurs at the start point of the heat exchanger's core, but as the flow proceeds to the end of the core, the velocity of every channel to be equalized.

Is it normal to be equalized the flow velocity in porous media? I have searched Ansys help and google, but nothing has come out.

Anybody knows how the flow proceeds in porous domain in CFX and why the flow uniformity occurs in porous media? and if I want to maintain the flow non-uniformity through the whole domain, how can I set up the solver?

Thank you in advance.

karachun · July 28, 2020, 05:12

Does flow channels have a common inlet part? If so then this looks reasonable. Fluid flows on a path of minimum resistance, higher speed mean greater resistance and higher energy losses.

I observe a similar effect when one user places some porous media after inlet with some swirling velocity profile (profile was used to model flow after fan). Flow rapidly becomes straight because swirled flow meahs longer path of elemental fluid particle and therefore higher resistance and therefore is not preferable from an energetic point of view.

CFXer · July 28, 2020, 07:11

Quote:

Originally Posted by karachun

Does flow channels have a common inlet part? If so then this looks reasonable. Fluid flows on a path of minimum resistance, higher speed mean greater resistance and higher energy losses.

I observe a similar effect when one user places some porous media after inlet with some swirling velocity profile (profile was used to model flow after fan). Flow rapidly becomes straight because swirlad flow meahs longer path of elemental fluid particle and therefore higher resistance and long path therefore is not preferable from an energetic point of view.

Yes, the flow channel is a long cuboid-shaped channel. (a plate shape)

So, you mean the flow must be mixed through the fluid channel, not only porous domain but also fluid domain?

karachun · July 28, 2020, 08:38

No, I mean that it is expected that porous medium enforce nonuniform speed field to become more uniform.

CFXer · July 28, 2020, 20:45

Oh I understand. Thank you!

July 28, 2020, 04:03	Flow distribution in porous domain (CFX)	#1
CFXer Member William Join Date: Jun 2020 Posts: 70 Rep Power: 6	Hello I am trying to simulate a heat exchanger as a porous media.(using CFX's porous domain) So it has several channels that have flow non-uniformity. I want to observe how the flow non-uniformity varies with the heat exchanger's header shape. In my pre-test, the flow non-uniformity occurs at the start point of the heat exchanger's core, but as the flow proceeds to the end of the core, the velocity of every channel to be equalized. Is it normal to be equalized the flow velocity in porous media? I have searched Ansys help and google, but nothing has come out. Anybody knows how the flow proceeds in porous domain in CFX and why the flow uniformity occurs in porous media? and if I want to maintain the flow non-uniformity through the whole domain, how can I set up the solver? Thank you in advance.

July 28, 2020, 05:12		#2
karachun Senior Member Join Date: Nov 2015 Posts: 246 Rep Power: 12	Does flow channels have a common inlet part? If so then this looks reasonable. Fluid flows on a path of minimum resistance, higher speed mean greater resistance and higher energy losses. I observe a similar effect when one user places some porous media after inlet with some swirling velocity profile (profile was used to model flow after fan). Flow rapidly becomes straight because swirled flow meahs longer path of elemental fluid particle and therefore higher resistance and therefore is not preferable from an energetic point of view. Last edited by karachun; July 28, 2020 at 08:35.

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July 28, 2020, 08:38		#4
karachun Senior Member Join Date: Nov 2015 Posts: 246 Rep Power: 12	No, I mean that it is expected that porous medium enforce nonuniform speed field to become more uniform.

July 28, 2020, 20:45		#5
CFXer Member William Join Date: Jun 2020 Posts: 70 Rep Power: 6	Oh I understand. Thank you!