Thermal Stratification

mokay · April 28, 2016, 09:38

Hi !

I'm a trainee and i need to study the thermal stratification inside a volume full of air. It's an helicopter cockpit.
So I have to use gravity function in Fluent
I choose incompressible ideal gas for air, and sutherland viscosity
I prescribed 0.039kg/s-340K of air at the entrance (a pipe), then it goes into the cockpit, and then through a pressure outlet with ambiant temperature -293K
I use energy equation, k-e realizable model, Coupled and Presto for pressure and 2nd order for the rest

but I can't see any thermal stratification in the results
Can you help me ?

LuckyTran · April 29, 2016, 17:24

Did you remember to enable gravity?

The outlet temperature is inconsequential unless there is backflow.

What are your thermal boundary conditions? These are very important because you have an inflow at uniform inlet temperature. Thermal stratification will not occur unless there is some heat transfer that produces a temperature gradient.

mokay · May 2, 2016, 03:49

Yes gravity is enabled.

My boundary conditions are mass flow inlet with 0.039kg/s-340K and a pressure outlet at 293K
the other are simply wall, adiabatic and convection

LuckyTran · May 2, 2016, 09:52

Check your thermal boundary conditions.

Remember, if there's no heat transfer, you don't produce any thermal gradients with a uniform inflow, then there won't be an thermal stratification.

April 28, 2016, 09:38	Thermal Stratification	#1
mokay New Member Moquay Ugo Join Date: Apr 2016 Posts: 3 Rep Power: 10	Hi ! I'm a trainee and i need to study the thermal stratification inside a volume full of air. It's an helicopter cockpit. So I have to use gravity function in Fluent I choose incompressible ideal gas for air, and sutherland viscosity I prescribed 0.039kg/s-340K of air at the entrance (a pipe), then it goes into the cockpit, and then through a pressure outlet with ambiant temperature -293K I use energy equation, k-e realizable model, Coupled and Presto for pressure and 2nd order for the rest but I can't see any thermal stratification in the results Can you help me ?

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April 29, 2016, 17:24		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,740 Rep Power: 66	Did you remember to enable gravity? The outlet temperature is inconsequential unless there is backflow. What are your thermal boundary conditions? These are very important because you have an inflow at uniform inlet temperature. Thermal stratification will not occur unless there is some heat transfer that produces a temperature gradient.

May 2, 2016, 03:49		#3
mokay New Member Moquay Ugo Join Date: Apr 2016 Posts: 3 Rep Power: 10	Yes gravity is enabled. My boundary conditions are mass flow inlet with 0.039kg/s-340K and a pressure outlet at 293K the other are simply wall, adiabatic and convection

May 2, 2016, 09:52		#4
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,740 Rep Power: 66	Check your thermal boundary conditions. Remember, if there's no heat transfer, you don't produce any thermal gradients with a uniform inflow, then there won't be an thermal stratification.