Learning Forum

[Edwin1211]

Hi Ansys Team, I hope this message finds you well.

I need to simulate the heating process of an air stream flowing inside a metallic pipe. The pipe is subject to a voltage potential, making electricity flow across the metal, releasing heat by the joule effect. The heat released is absorbed by the air stream, increasing its temperature. The outlet temperature of the air stream is in the range 800C - 1000C, while the pipe can reach 1100C - 1200C at its hottest point. The diameter of the pipe is in the range of 0.5in - 5in. Please find attached a representation of the process

Given the high temperature of the process and the small diameter of the pipe, radiation plays an important role in heat transfer. Unfortunately, I am not sure what radiation model would be the most appropriated to use in the simulation.

Could you please help me with this? :)

Thank you

[Karthik Remella]

Hello The question you will need to answer is if air is going to be a participating medium or not. Generally, the air is optically thin and has zero absorption as well as scattering. If this is the case in your simulation, then air is non-participating and you can use the Surface to Surface radiation model. If the working fluid is participating, then I would use the DO model. DO model is substantially more expensive compared to S2S.
Please have a look at the link here.
5.3.1. Overview and Limitations (ansys.com)
Karthik

[Edwin1211]

Hi Kremella. Thanks for your answer
How could I know if the air is participating? Maybe running one simulation with S2S and another with DO and comparing or is there another way to determine it?

[Karthik Remella]

Hello You could calculate the optical thickness of the medium. Air is generally optically thin and any radiation exchange is between the surfaces.
Karthik