Flow though Heated Pipe - thermalSimpleFoam

ayushrai · March 30, 2021, 08:17

Dear Foamers,

I am very new to OpenFOAM and hence, kindly pardon me if my doubt appears too trivial and dumb. I had read couple of previous OpenFOAM threads about implementation of temperature in simpleFoam, but none of them worked in my case. I am using OpenFOAM-2.4.0-MNF version.

Problem Description : I am simulating a case in which a cold fluid (293K) flows inside a pipe, whose wall is at constant temperature (353K). The pipe is linearly converging in nature with inlet diameter of 10 cms and outlet diameter of 6 cms. The fluid enters the pipe at 5 m/seconds. The flow is incompressible, steady-state and laminar in nature due to which I chose simpleFoam to model this problem.

Since, there are only pressure and velocity fields in simpleFoam, I decided to add temperature equation to it and name it as thermalSimpleFoam. In case of geometry, I created a wedge with small angle of 4 degrees and sufficiently long length (such that it exceeds entrance length). Moreover, I also modified one of the boundary conditions, totalTemperature, and renamed it to convectiveHeatTransfer to implement boundary condition for the Wall.

Issue : My simulation ran successfully without any issue but the results are not satisfying. Analytically in such cases, I expect a parabolic profile for temperature variation from center towards the wall, but I got very weird results.

I have attached thermalSimpleFoam solver codes, case files with time directories (for usage by ParaView to visualize the flow) and boundary condition, convectiveHeatTransfer files as well for your kind reference. The files can be downloaded from the link mentioned below:
https://we.tl/t-oKMPnAS3R1

I, therefore, request you to please take a look at those files and settings, and let me know possible mistakes and corresponding rectifications. I would be highly obliged for your act of kindness.

Thanks

agustinvo · March 31, 2021, 04:23

Hi,

I see that you implemented a BC to run this case. Have you tried to use fixedValue for T? I think that is simpler than implementing a BC, at least for a fast check of your solver.

ayushrai · March 31, 2021, 05:22

Dear Agustin,

First of all, thanks to you very much for investigating my issue. I appreciate you for taking your time. I had tried that but it didn't give me desired result still. I gave the wall temperature as 900K and fluid inlet temperature as 300K but after completion of simulation, when I plotted the graph of temperature variation along the axial length of pipe, I got weird results. I have attached the image here for your kind reference.

Graph Description : The entire graph is plotted along the centerline of the pipe which is basically the bottom line of the wedge. The x-axis starts from the centerline at inlet and ends at the centerline at outlet (hence, total length is 2 meters). The y-axis shows the variation of temperature along the centerline of the pipe.

Issue : I expect the graph to be slightly increasing from cold temperature (300K) at the start towards somewhat higher temperature (but less than 900K) at the end. But this graph shows that the fluid becomes as hot as that of wall very early which seems unphysical to me.

Your suggestions would be highly appreciated.

Image Link : https://pasteboard.co/JV8hrGv.png

Thanks

March 30, 2021, 08:17	Flow though Heated Pipe - thermalSimpleFoam	#1
ayushrai New Member Laura Parent Join Date: Feb 2021 Posts: 3 Rep Power: 5	Dear Foamers, I am very new to OpenFOAM and hence, kindly pardon me if my doubt appears too trivial and dumb. I had read couple of previous OpenFOAM threads about implementation of temperature in simpleFoam, but none of them worked in my case. I am using OpenFOAM-2.4.0-MNF version. Problem Description : I am simulating a case in which a cold fluid (293K) flows inside a pipe, whose wall is at constant temperature (353K). The pipe is linearly converging in nature with inlet diameter of 10 cms and outlet diameter of 6 cms. The fluid enters the pipe at 5 m/seconds. The flow is incompressible, steady-state and laminar in nature due to which I chose simpleFoam to model this problem. Since, there are only pressure and velocity fields in simpleFoam, I decided to add temperature equation to it and name it as thermalSimpleFoam. In case of geometry, I created a wedge with small angle of 4 degrees and sufficiently long length (such that it exceeds entrance length). Moreover, I also modified one of the boundary conditions, totalTemperature, and renamed it to convectiveHeatTransfer to implement boundary condition for the Wall. Issue : My simulation ran successfully without any issue but the results are not satisfying. Analytically in such cases, I expect a parabolic profile for temperature variation from center towards the wall, but I got very weird results. I have attached thermalSimpleFoam solver codes, case files with time directories (for usage by ParaView to visualize the flow) and boundary condition, convectiveHeatTransfer files as well for your kind reference. The files can be downloaded from the link mentioned below: https://we.tl/t-oKMPnAS3R1 I, therefore, request you to please take a look at those files and settings, and let me know possible mistakes and corresponding rectifications. I would be highly obliged for your act of kindness. Thanks

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March 31, 2021, 04:23		#2
agustinvo Senior Member Agustín Villa Join Date: Apr 2013 Location: Alcorcón Posts: 314 Rep Power: 15	Hi, I see that you implemented a BC to run this case. Have you tried to use fixedValue for T? I think that is simpler than implementing a BC, at least for a fast check of your solver.

March 31, 2021, 05:22		#3
ayushrai New Member Laura Parent Join Date: Feb 2021 Posts: 3 Rep Power: 5	Dear Agustin, First of all, thanks to you very much for investigating my issue. I appreciate you for taking your time. I had tried that but it didn't give me desired result still. I gave the wall temperature as 900K and fluid inlet temperature as 300K but after completion of simulation, when I plotted the graph of temperature variation along the axial length of pipe, I got weird results. I have attached the image here for your kind reference. Graph Description : The entire graph is plotted along the centerline of the pipe which is basically the bottom line of the wedge. The x-axis starts from the centerline at inlet and ends at the centerline at outlet (hence, total length is 2 meters). The y-axis shows the variation of temperature along the centerline of the pipe. Issue : I expect the graph to be slightly increasing from cold temperature (300K) at the start towards somewhat higher temperature (but less than 900K) at the end. But this graph shows that the fluid becomes as hot as that of wall very early which seems unphysical to me. Your suggestions would be highly appreciated. Image Link : https://pasteboard.co/JV8hrGv.png Thanks