[ANSYS Meshing] Fluent Conjugate heat transfer: Temperature at a small fluid region exceed limit

RPjack · August 17, 2015, 20:31

Learned a lot from the forum. Hope my first thread will help me solve the problem.

Fluent Conjugate heat transfer analysis. Temperature at a small fluid region is extremely high.

It is power module forced liquid cooling analysis, heat generated at the die, conducted through several layers of solid, then dissipate via pin fin heat sink to the fluid. Mass flow inlet and pressure outlet. Coolant temperature 300K. Temperature in a small region near heatsink fins (see image) diverged after ~100 iterations.

Temperature at most liquid region is reasonable(~300K). However temperature of a small portion of liquid is over 3000K(https://www.dropbox.com/s/0eqjt4me2q...htemp.png?dl=0), where temperature of a nearby small region is only ~57K. (https://www.dropbox.com/s/bvny7gadmm...wtemp.PNG?dl=0)

During iteration, at first, “Reversed flow in xx faces on pressure-outlet” appeared after ~100 interactions. After another 20 iterations, message “ temperature limited to 1.000000e+00 in 6 cells on zone 18 in domain 1, temperature limited to 5.000000e+03 in 1 cells on zone 18 in domain 1” appeared. See regions with extreme high and low temperature

Thanks to old forum discussion(http://www.cfd-online.com/Forums/flu...879-cells.html) , I think mesh is the problem. Here, ANSYS mesh is used (see https://www.dropbox.com/s/5ga2bnep39...ction.PNG?dl=0)
1. Sweep mesh at the most solid
2. Prism mesh defined at fluid/solid interface

Any suggestion how to improve mesh is greatly appreciated!!!

Tried to use ANSYS meshing (Tgrid), Generate Prisms mesh successfully, but could not mesh the rest fluid region with tetra mesh, the error message “Non-triangular surface mesh”

Thanks in advance!

May19 · June 20, 2019, 07:11

dear sir,
I am simulating a pipe flow with polynomial function of temperature of all properties for Re 30000 and inner and outer diameter of pipe 0.02 & 0.025 m me too is suffering with same issue in starting 20 iteration it shows reverse flow in xxx cells at outlet and after that Temp limited to 5000 & 1000 K in my fluid and solid domain respectively also after that Cp value reported to be negative and AMG solver gets diverge....

Please if you find the solution of the same then please help me out...

Thanks in advance.

August 17, 2015, 20:31	Fluent Conjugate heat transfer: Temperature at a small fluid region exceed limit	#1
RPjack New Member Jackie Stan Join Date: Jul 2015 Posts: 3 Rep Power: 10	Learned a lot from the forum. Hope my first thread will help me solve the problem. Fluent Conjugate heat transfer analysis. Temperature at a small fluid region is extremely high. It is power module forced liquid cooling analysis, heat generated at the die, conducted through several layers of solid, then dissipate via pin fin heat sink to the fluid. Mass flow inlet and pressure outlet. Coolant temperature 300K. Temperature in a small region near heatsink fins (see image) diverged after ~100 iterations. Temperature at most liquid region is reasonable(~300K). However temperature of a small portion of liquid is over 3000K(https://www.dropbox.com/s/0eqjt4me2q...htemp.png?dl=0), where temperature of a nearby small region is only ~57K. (https://www.dropbox.com/s/bvny7gadmm...wtemp.PNG?dl=0) During iteration, at first, “Reversed flow in xx faces on pressure-outlet” appeared after ~100 interactions. After another 20 iterations, message “ temperature limited to 1.000000e+00 in 6 cells on zone 18 in domain 1, temperature limited to 5.000000e+03 in 1 cells on zone 18 in domain 1” appeared. See regions with extreme high and low temperature Thanks to old forum discussion(http://www.cfd-online.com/Forums/flu...879-cells.html) , I think mesh is the problem. Here, ANSYS mesh is used (see https://www.dropbox.com/s/5ga2bnep39...ction.PNG?dl=0) 1. Sweep mesh at the most solid 2. Prism mesh defined at fluid/solid interface Any suggestion how to improve mesh is greatly appreciated!!! Tried to use ANSYS meshing (Tgrid), Generate Prisms mesh successfully, but could not mesh the rest fluid region with tetra mesh, the error message “Non-triangular surface mesh” Thanks in advance!

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June 20, 2019, 07:11		#2
May19 Member Mayank Join Date: May 2019 Location: India Posts: 30 Rep Power: 6	dear sir, I am simulating a pipe flow with polynomial function of temperature of all properties for Re 30000 and inner and outer diameter of pipe 0.02 & 0.025 m me too is suffering with same issue in starting 20 iteration it shows reverse flow in xxx cells at outlet and after that Temp limited to 5000 & 1000 K in my fluid and solid domain respectively also after that Cp value reported to be negative and AMG solver gets diverge.... Please if you find the solution of the same then please help me out... Thanks in advance.