Microchannels Reactor

JoanaAndrade · March 4, 2013, 12:39

Hello!
I'm new in CFX and I have to model a microchannel reactor. It has an cylindrical inlet (7,2 mm diameter) connected with a cubic part (10 mm side). From this cubic part to the outlet (that is symmetrical) there are a lot of microchannels (1mm side). After setting up, when I'm gonna see the results, there is no way the flow goes through the microchannels.
Can someone help me?

ghorrocks · March 4, 2013, 16:26

Please post an image of what you are modelling, and some details about the fluid and boundary conditions.

JoanaAndrade · March 6, 2013, 12:55

It is like that. First, I'm trying to make a water flow. In the inlet, the flow rate range is between 0.25 and 250 g/min. In the outlet, relative pressure = 0.

ghorrocks · March 6, 2013, 17:15

Is it correct that one fluid flows through the orange channels and another through the blue channels and they cannot mix? If so then this is a trivial flow to model. There will be something simple wrong with your set up. If it is more complex then this please explain in more detail.

JoanaAndrade · March 7, 2013, 14:05

Yes, they cannot mix. I know it seems trivial, but the fluids just don't go through the channels. It goes like that. The set up is very simple, It's just water and air, no heating. And I've already increased the flow rate, and it was just the same. I'm wondering if there something wrong with meshing. I've just generate the standard mesh, no changes.

evcelica · March 7, 2013, 16:20

Looks like it goes through the channels to me? Inlets are on the top and the left? Maybe you think it doesn't because the streamline don't go all the way through? That doesn't mean the flow stopped.

JoanaAndrade · March 11, 2013, 10:55

Really? I tought so... And how do I know it is ok? Isn't the streamlines supposed to show the way the flow travels?

oj.bulmer · March 11, 2013, 15:09

If I am not missing something, this seems perfectly normal. If you have fully converged the solution, what is the domain imbalance for both the fluids? If it is less than (at least) 1% it should be alright. For better results, I would run till the domain imbalances are less than 0.01%, if it can be afforded.

OJ

ghorrocks · March 11, 2013, 16:38

Yes, the streamlines show the flow travel. But they are numerically integrated over the solution dataset and therefore are approximations. When you have long thin channels they do tend to wander a little and if they hit a wall they will stop.

March 4, 2013, 12:39	Microchannels Reactor	#1
JoanaAndrade New Member Joana Andrade Join Date: Feb 2013 Posts: 5 Rep Power: 13	Hello! I'm new in CFX and I have to model a microchannel reactor. It has an cylindrical inlet (7,2 mm diameter) connected with a cubic part (10 mm side). From this cubic part to the outlet (that is symmetrical) there are a lot of microchannels (1mm side). After setting up, when I'm gonna see the results, there is no way the flow goes through the microchannels. Can someone help me?

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March 4, 2013, 16:26		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,700 Rep Power: 143	Please post an image of what you are modelling, and some details about the fluid and boundary conditions.

March 6, 2013, 17:15		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,700 Rep Power: 143	Is it correct that one fluid flows through the orange channels and another through the blue channels and they cannot mix? If so then this is a trivial flow to model. There will be something simple wrong with your set up. If it is more complex then this please explain in more detail.

March 7, 2013, 16:20		#6
evcelica Senior Member Erik Join Date: Feb 2011 Location: Earth (Land portion) Posts: 1,167 Rep Power: 23	Looks like it goes through the channels to me? Inlets are on the top and the left? Maybe you think it doesn't because the streamline don't go all the way through? That doesn't mean the flow stopped.

March 11, 2013, 10:55		#7
JoanaAndrade New Member Joana Andrade Join Date: Feb 2013 Posts: 5 Rep Power: 13	Really? I tought so... And how do I know it is ok? Isn't the streamlines supposed to show the way the flow travels?

March 11, 2013, 15:09		#8
oj.bulmer Senior Member OJ Join Date: Apr 2012 Location: United Kindom Posts: 473 Rep Power: 20	If I am not missing something, this seems perfectly normal. If you have fully converged the solution, what is the domain imbalance for both the fluids? If it is less than (at least) 1% it should be alright. For better results, I would run till the domain imbalances are less than 0.01%, if it can be afforded. OJ

March 11, 2013, 16:38		#9
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,700 Rep Power: 143	Yes, the streamlines show the flow travel. But they are numerically integrated over the solution dataset and therefore are approximations. When you have long thin channels they do tend to wander a little and if they hit a wall they will stop.