Heat Flux at boundary inconsistency

ashishmagar600 · March 7, 2020, 02:00

Hello Everyone..!

I am trying to simulate a shell and tube heat exchanger (STHX) case, wherein I solve for flow and heat using chtMultiRegionSimpleFoam.

I obtained heat flux through each tube wall as around 50000 W/m2.

However, when I tried a case with a single tube with walls and giving 50000 W/m2 as out-flux (meaning negative flux) at the outer solid walls of the tube, I am getting temperatures below 273K. The simulation with the complete geometry of SHTX did run properly and had reasonable temperature values.

This is just a study I am doing to observe the behavior of each tube.

Any suggestions?

ashishmagar600 · March 10, 2020, 02:22

Just to add to my question, when I give flux in terms of Heat Transfer coefficient and ambient temperature I am getting a solution as expected.

Any reason why this is happening?

crubio.abujas · March 10, 2020, 04:18

Could it be that either of the heat fluxes [W/m2] you mentioned where actually a heat flow [W]? That may explain the radical difference in the behaviour when setting the value and that the differences disapeared when using a heat transfer coefficient.

ashishmagar600 · March 10, 2020, 05:53

I specifically checked that I was not doing this mistake.

March 7, 2020, 02:00	Heat Flux at boundary inconsistency	#1
ashishmagar600 Member Ashish Magar Join Date: Jul 2016 Location: Mumbai, India Posts: 81 Rep Power: 9	Hello Everyone..! I am trying to simulate a shell and tube heat exchanger (STHX) case, wherein I solve for flow and heat using chtMultiRegionSimpleFoam. I obtained heat flux through each tube wall as around 50000 W/m2. However, when I tried a case with a single tube with walls and giving 50000 W/m2 as out-flux (meaning negative flux) at the outer solid walls of the tube, I am getting temperatures below 273K. The simulation with the complete geometry of SHTX did run properly and had reasonable temperature values. This is just a study I am doing to observe the behavior of each tube. Any suggestions?

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March 10, 2020, 02:22		#2
ashishmagar600 Member Ashish Magar Join Date: Jul 2016 Location: Mumbai, India Posts: 81 Rep Power: 9	Just to add to my question, when I give flux in terms of Heat Transfer coefficient and ambient temperature I am getting a solution as expected. Any reason why this is happening?

March 10, 2020, 04:18		#3
crubio.abujas Senior Member Carlos Rubio Abujas Join Date: Jan 2018 Location: Spain Posts: 127 Rep Power: 9	Could it be that either of the heat fluxes [W/m2] you mentioned where actually a heat flow [W]? That may explain the radical difference in the behaviour when setting the value and that the differences disapeared when using a heat transfer coefficient.

March 10, 2020, 05:53		#4
ashishmagar600 Member Ashish Magar Join Date: Jul 2016 Location: Mumbai, India Posts: 81 Rep Power: 9	I specifically checked that I was not doing this mistake.