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Temperature and heat flux wall boundary condition

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Old   February 1, 2014, 04:32
Default Temperature and heat flux wall boundary condition
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Hamid
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Dear All,

In my model, I have a coil which transfers the heat flux 5000 w/m2 to gasoline. I set the wall of coil boundary condition by this heat flux. After convergence the model, I checked the surface temperature of the coil. It was 1000 K. But In real, the surface temperature of the coils shouldn't exceed 400 K. How can I control the temperature and heat flux of the coil?


Any help would be appreciated
Hamid
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Old   February 1, 2014, 14:00
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Hamid Zoka
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where does the 5000 w/m2 come from?
It seems that heat flux is highly over predicted.
could you give an image of your computation domain plus boundaries defined?
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Old   February 2, 2014, 01:05
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Hamid
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Quote:
Originally Posted by Hamidzoka View Post
where does the 5000 w/m2 come from?
It seems that heat flux is highly over predicted.
could you give an image of your computation domain plus boundaries defined?

Dear Hamidzoka,

I have a gasoline tank with 46 m diameter and 13 m height. two row of coils are located near the bottom of the tank. the initial temperature of gasoline is -5 C. By this Coils it should be heated to 9 C. the coils flux is come from steam which is flows through the inner side of the coils. the coils length is 200 m with spiral shape. the coils diameter is 115 mm.

in fact the gasoline is heated by free convection. the flow regime is turbulent. (Ra > 10^9) I have set fixed temperature of ambient for B.C of the tank walls (side walls, bottom wall and top wall).

Sincerely
Hamid
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Old   February 22, 2014, 22:10
Default Value of Q
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Abhijeet Shrawage
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As the previous poster suggested...maybe try recalculating the value of the heat flux applied.
you have dT of 14C.
You know the surface area of the heat source (heating coil). Use the simple formula.
q=\overline{m}*Cp*\DeltaT

If Cp is varying, then substitute Cp with dH; the change in enthalpy of gasoline at -5C and 14C.

If again you get the same answer, then try double checking if you have put the right thermophysical properties of Gasoline in your FLUENT material database.
Things like low Cp or high thermal conductivity can be the cause of this as well.

Best of Luck.

Abhijeet
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