[NightWing]

Hi All,

Recently i have been trying to learn ansys_fluent. I was trying to model a simple tube which is exposed to radiation intensity and air is following inside the tube. My aim was to study how much of the heat that falls on the tube walls gets carried away by air following inside the tube. The conduction part has been neglected.

For that i tried to input the tube walls (the tube outer side) as heat flux condition, say about 400 W/m2 . But in fluent i noticed that we can directly specify only heat flux with the units W/m2. I dont know how in fluent they calculate the heat flux based on what area?

my problem if am not wrong, as radiation intensity falls on the tube surface, the wall of tube gets heated up. as it falls on entire length of tube, my area will be 2*pi*r*L (surface area). So if i specify 400 W/m2 directly does it mean that in fluent it is Q/2*pi*r*L of my case???

moreover, can i use this formulae: as radiation falls on tube surface, suppose its coated black, then Q/A = epsilon*sigma* (Tw^4 - Ta^4) . and as air is following inside, the heat carried away by air is mcp*dt?

if not pls correct me

[LuckyTran]

Originally Posted by NightWing

For that i tried to input the tube walls (the tube outer side) as heat flux condition, say about 400 W/m2 . But in fluent i noticed that we can directly specify only heat flux with the units W/m2. I dont know how in fluent they calculate the heat flux based on what area?

Heat flux should have units of W/m^2 and is independent of any area, it's heat per unit area. It could be W/in^2 or W/mm^2. I think you have the wrong definition of heat flux.

[NightWing]

Actually, the way i described was wrong.

I agree that heat flux is independent of area. I wanted to know whether of i choose 20 boundaries and name it as a single patch, will the heat flux specified be taken individually for all the 20 boundaries as such or will it get divided by 20.


However i figured it out I have solved the problem.

Thank you all !!!!