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Temperature not converging in counter mixing flow

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Old   April 15, 2018, 16:33
Default Temperature not converging in counter mixing flow
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Sathish
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Hi guys,

Im simulating a counter mixing flow (water) in which water with 293K (cold inlet) meets hot water (673K of hot inlet) in the middle and then flows down to the outlet. The water region is surrounded by solid steel which is turn surrounded by air. I have set the mass flow rate for both inlets and outflow for the outlet. I have written udf for the water properties namely the density, thermal conductivity, viscosity and specific heat capacity as function of temperature for the given fixed operating pressure of 35MPa.
I started the steady state simulation (hybrid initialisation) using the fixed values of water properties (default setup) and after around 80 iterations, the calculation is completed. Then, i changed the water properties from the constant default values to the udf that i hav previously loaded and ran further iterations, also in steady state. By doing this, i could avoid getting the ''error: segmentation fault''. All the values (velocities, continuiity, k & epsilon) seems to converge after a further 50 iterations except for the temperature which remains plateau ( refer Fig below). furthermore, there are ''temperature limited to XXX'' warning in the consoles once i start running using the udf (refer to fig below). i tried all the solutions discussed in this forum such as setting a lower relaxation factor, refining mesh, set the temp limits to 250 K (min) and 720 K (max), yet there is no improvement...been stuck at this for the past 2 days...hope u guys can share your expertise a bit..the udfs are very simple and i hav attached them in here ( refer below)..im not sure whether its the udf or the solution controls causing this headache...thanks in advance
Attached Images
File Type: png residual.PNG (25.0 KB, 10 views)
File Type: png error_temperature_limited.PNG (4.5 KB, 5 views)
Attached Files
File Type: c Cp_35.c (2.0 KB, 1 views)

Last edited by Sam_1913; April 24, 2018 at 07:04.
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Old   April 16, 2018, 11:51
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Sathish
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Any help would be great...Thanks

Last edited by Sam_1913; April 24, 2018 at 07:05.
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convergence failure, counterflow, fluent, temperature limited, udf code

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