Problem defination:
Annular water domain is created due to glass and steel pipe of which glass is having dia more than that of steel.glass pipe has 5mm thickness and steel pipe of 1mm thickness.Water is closed from both the ends and no heat is transferred from ends of pipe(water, steel glass).Inner surface of steel pipe is open to atmosphere and outer surface of glass pipe is exposed to radiation intensity of 800W/m2. Length of domain is 1m.Initial Temperature of water is 300K.
I have to find change in temperature of water and radiative heat flux distribution in the water from the glass upto steel.
for solving this problem in fluent I have to use DO(discrete radiation) model.
so,
1. what should be the boundary conditions for this problem?
2. How radiation heat flux is to be applied on glass outer surface?
3. Is there any need of considering air domain as inner surface of steel is open to atmosphere?
4. How to set initial temperature of water as it is closed from both the ends?
You may address the problem as:
1. It can be treated as a case of constant heat flux.
3. The space between the glass and the tube is evacuated, As a first step, assuming 100% energy is transmitted to the outer surface of the tube, the analysis may be undertaken with the incident heat flux.
4. You may assume an initial temperature of 300K.
Check if the last point 4 is appropriate to your problem.
Thanks for reply Mr.K.V. Sharma........................however I have following doubts regarding solar irradiation flux on the tube outer surface.
1. I am setting direct Solar Irradiation of 800W/m2 in radiation tab and nothing in the thermal tab. So If I specify some value for heat flux in thermal will this be proper BC for solar problem? Because after specifying this value answers are different.
2. In beam direction section I have set value y=1 which gives incident radiation applied in y direction only as shown in figure. But I need radiation on full wall that is not in particular direction.
Mr. Paul,
1. What is the difference in the values between radiation and thermal conditions?
2. Since the radiation at the surface is conducted by the tube material, the BC should be acceptable.
3. Since complete vacuum is not feasible, certain amount of heat loss is inevitable.
4. What is your means for validation of the results? Experimental data will differ with theoretical results from Fluent.
5. What do you mean by "I need radiation on the full wall" Explain.
1. As glass is transparent I applied direct irradiation flux 700W/m2 in radiation tab and 100W/m2 as diffuse Irradiation flux in radiation tab. Now if I apply heat flux of 700W/m2 in the thermal tab, is this proper way to deal with solar radiation falling on glass wall?
2. There is water enclosed in the glass pipe(no vacuum)
3. I need radiation heat flux on entire wall of glass.
Hi Mr Paul,
Did you find out whether you should keep the thermal tab clear or include heat flux?
Thanks
I also have similar problem.. I want to include heat flux and radiation loss on the same surface as boundary conditions. Since due to heat flux temperature will increase and loss by radiation will be significant.
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