TAGGED: #fluent-#ansys, #heat_exchanger
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December 19, 2024 at 9:02 pm
merveala01
SubscriberI am doing analysis in laminar flow and energy equations on. It is so simple. I know hot water and cold water inlet temperature values. Hot water varies between 25 and 55 degrees and cold water inlet is 20 degree as constant. and want to calculate outlet temperatures but I can not get sensible results about cold water outlet. for example even hot fluid water is 55 degree, the cold water outlet is 25 degree. I defined all the variables as parameter set. specific heat, viscosity, mass flow rate and density are other variables. Finally, I decided to write an equation for the walls. Because for an inlet temperature of 55 degrees, the outlet temperature should be around 45 degrees. But I don't know how to write the UDF function when I have so many parameter
variables.
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December 20, 2024 at 11:07 am
Rob
Forum ModeratorIn CFD we'd tend to set the inlet value and calculate the outlet condition. So, in your case you can't force a fixed dT but instead need to understand why it might differ from the experiment. In your case I suspect there is no connection between the hot & cold zones so revisiting the geometry to apply "share topology" might be a good place to start.Â
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December 20, 2024 at 11:28 am
merveala01
SubscriberI followed that video and it applies share topology. What else can ı do?
https://youtu.be/rFQisXCwLXI?si=cvkXZJVprKOWpakL
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December 20, 2024 at 11:57 am
Rob
Forum ModeratorWhat setting have you applied to the wall & shadow pairs?Â
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December 20, 2024 at 11:58 am
merveala01
SubscriberI didnt set any setup for wall they were default
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December 20, 2024 at 12:00 pm
Rob
Forum ModeratorOK, and what is the heat flux (Flux Report) through those walls?
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December 20, 2024 at 12:11 pm
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December 20, 2024 at 1:12 pm
Rob
Forum ModeratorIn Fluent please report the flux on the wall & shadow pair. If you aren't getting results you expect you need to investigate in the solver, not just check the few monitors you have in Workbench.Â
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December 20, 2024 at 1:19 pm
merveala01
SubscriberI reported and all of them are zero :(
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December 20, 2024 at 1:31 pm
Rob
Forum ModeratorPlease post a screen shot. And one of the wall bc panel.Â
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December 20, 2024 at 2:08 pm
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December 20, 2024 at 2:17 pm
Rob
Forum ModeratorThat middle image - the wall setting is not the default. That should be coupled and then set the material & thickness in one or other of the pair. Otherwise Fluent has no way to pass heat between the two sides, and that's likely why your hot channel isn't cooling & the cool channel isn't warming.Â
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December 20, 2024 at 3:48 pm
merveala01
SubscriberI give 0.001m thickness both intermediate walls and side walls. But there isn't much more difference. maybe 0.05 change value. I need more
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December 23, 2024 at 9:57 am
Rob
Forum ModeratorHave you switched the interior walls back to coupled?Â
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