Radiation heat transfer in channel flow

[VYT]

Summary:

Does radiation heat transfer occurs between in a channel flow?

Main Question or Discussion Point

Hi guys, I am confused about the heat transfer mode of between two contacting material, especially in a channel flow.

Obviously, conduction or convection dominate the heat transfer process in the process with low object temperature .

But I am not sure if I have a fluid of 500 Kelvin, flowing in the the steel pipe that is exposed to air, does radiation heat transfer occurs between the fluid and the contacting surface?

The only reason I can think of to reject the idea above is that temperatures of two contacting materials are too closed that radiation is not occuring.

Am I right about it, and is there other reasons behind it? Thank you!

 

[trurle]

But I am not sure if I have a fluid of 500 Kelvin, flowing in the the steel pipe that is exposed to air, does radiation heat transfer occurs between the fluid and the contacting surface?

Generally thermal radiation contribution in your case would be small.

If your fluid is gas at atmospheric pressure, the radiation thermal resistance at 500K is similar to conductance thermal resistance of boundary layer in case of laminar flow, but most gases are transparent in thermal IR at length scale of centimetres, therefore not emitting IR efficiently. IR contribution may be important if you have very large diameter tube or very emissive mix of gases, preferable both. I. e. something like flue gas in chimney stack.

If your "fluid" is liquid, it have high enough thermal conductivity to make radiation transfer contribution negligible, due liquid becoming nearly isothermal with pipe.