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 kerker September 14, 2010 01:17

floworks application

I’d like to simulate an engineering example using floworks as following:

There’s a section of solid material in a vertical stainless steel, gas with high temperature flow continuously from the inlet of the stainless steel to heat the solid material to the expected temperature in the stainless steel, I’d like to know the gas temperature vs. time after flowing out the solid material.

Is there anyone can give me some advice or the similar example.

Thanks for help.

 Boris_M September 21, 2010 08:21

I'm not quite sure if I understood your question correctly.

I assume you want to heat a solid geometry (doesn't mater what material) with a hot gas flow around it.
In this case you can simply use a time depending analysis where you define the maximum time and the time steps you what to get results to visualize. Then use a volume goal solid temperature for min, max and average so you would see the curve the material heats for each value over time. The only thing left is to define the rest of the project such as inflow etc. and the manual time step since otherwise the solver would decide and would do very small time steps like micro seconds and depending how long the overall time is it would take you years to solve with so small steps. But consider that to large steps can be to big to handle what happens in between the steps.
So it all depends a little on how fast you want the calculation, how long the overall time is and how large and detailed the model is.
As an example you can do 10 min time of a simple model in a few seconds steps easily in a few minutes or hours (depending what you think as simple model).
You can also use a stationary solution without heat transfer as initial condition for the transient simulation with heat transfer giving the solid block an initial condition for its starting temperature. With that the flow is already developed and the block will heat up from that point on. This is then neglecting the short time span the flow would initialize within a few seconds that would usually not be necessary if the overall time is much longer.

Regards,
Boris

 kerker September 26, 2010 21:57

Hi, Boris
Thank you very much!

I still have some questions.
Yes, I want to heat a solid geometry with a hot gas flow around it.
You said I can use a volume goal solid temperature for min, max and average. But the solid temperature is not the flow gas temperature; I’d like to know the flow gas transient temperature outlet of the solid geometry.
I defined two boundary conditions, one is the Inlet mass flow (the hot flow gas) located at the inlet of the solid geometry, and the other is a static pressure located at the outlet of the solid geometry, can I defined the volume goals of temperature of fluid? Dose “Temperature of fluid” in the floworks what I want? I have tried it, but it looks like no result, also have no error warnings.

Best regards,
kerker

 Boris_M October 11, 2010 16:20

I cannot tell if your project is set up correctly but as an example imagine a pipe with a block in it that has a heat source and a very low flow is going through the pipe so you can see a considerable temperature in the flow at the end of the pipe after the fluid got heated by the heat source.
If you apply a surface goal with fluid temperature on the outlet where your pressure boundary condition is then it gives you the fluid temperature at the outlet and depending if you used min, max or av the corresponding value. The same goes for transient analysis if for example the heat source has an initial temperature and get's cooled by the flow until it is cold then the transient temperature at the outlet is hot in the beginning and gets colder over time since the hot body also gets colder.

So everything should work just fine. If it doesn't then you probably made a mistake in your project definition.
Maybe check if the timestep is large enought so you see a result in a corresponding time frame. It can be that it does mirco second steps since too much is happening. You probably will have to set the manual time step larer but not too large otherwise you get instability in solving the process which might lead to a crash.

Boris

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