[Jammy]

First of all I would like to mention in detail about my project. I have to design a helical coil inside which flows cold water. Now hot air is passed over the coil in the cross flow direction. I have to form a boundary layer over the helical coil to show the boundary layer of air on the coil surface.

Please reply.

[-mAx-]

You have 2 separated flows: one with cold water inside the tube, and one outside the tube with air.
Is it right?
pictures may help

[Jammy]

Dear Sir,

Thank you for showing your concern in my problem.

I have two separated flows. Inside the helical coil coolant which is water in my case is flowing. Outside the helical coil air is flowing over it. I have three figures. In fig. 1, a straight helix is shown with inlet and outlet and air flow direction. This is my overall study which I have to do.

In fig. 2, I have shown one turn of helix inside a box. The box is nothing but Air domain. Gambit meshing is done. In fig 3, only I have changed the orientation of fig.2 to make view clear.

Now I have to do the heat transfer study. I thought to create a Boundary layer of air over the tube surface. i think I have made my problem clearer. How should I proceed?

Please help.

[-mAx-]

Do you have a thickness of your coil? Or is it simply baffle (one surface without a thickness)?
You will have to compute thermal conduction in the coil (heat transfer between both domains)
https://www.sharcnet.ca/Software/Flu...ug/node573.htm

BL is not nesseray first, I would try without BL for checking if your heat transfer is working

[Jammy]

Sir,

My wall has zero thickness. I am just considering convection on both sides of the coil. Actually I am unable to proceed as I am confused on how to calculate the overall heat transfer coefficient in this problem.

Should I calculate the inner heat transfer coefficient first or some other process. Please suggest as I am in deep need.
Thank you.

[-mAx-]

If you consider convection on both sides of the coil you will have to set the termal BC on the walls.
But you want to transfer the thermal condition from one side to the other side.
Tha's why you need to handle conduction in the shell
That's my opinion, (I never did such calculation)

[Jammy]

Sir, if I consider a straight helix inside which cold water say at a temperature of 5 degree Celsius is flowing. I have considered a constant wall temperature (100 degree Celsius) as the boundary condition of the helical tube wall. Inlet as "velocity inlet'' and outlet as ''outflow''.

In this how will I calculate the inner heat transfer coefficient. Can you please suggest.

[-mAx-]

If you don't consider the extern flow over the coil, then check the tutorial:
https://www.sharcnet.ca/Software/Flu...l/tg/node9.htm

[Jammy]

Thank you Sir. This link is really helpful for internal flow inside a tube. If in future I need some suggestions regarding heat transfer then can I ask you in this thread?

[Jammy]

Hello Max Sir,

My problem is based on a condenser. Steam is condensing on the outer surface of a thin-walled circular tube of diameter D = 50mm and length L = 6m maintains a uniform outer surface temperature of 100C. Water flows through the tube at a rate of 0.25 kg/s, and its inlet and outlet temperatures are Ti = 15C and To= 57C. What is the average convection coefficient associated with the water flow? Please suggest how to to find the avg heat transfer coeff. in fluent.