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VISCOUS DISSIPATION at the rotating flow

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Old   April 20, 2018, 17:37
Post VISCOUS DISSIPATION at the rotating flow
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hi guys

I am using Star-CCCM+ to simulate the heat transfer in a rotating pipe.

I found the rise of flow temperature is HIGHER at high rotating speed.

The input heat is always the same. All the heat are transferred to the flow.

But i do not know why the rise of flow temperature is different? They should be always the same. Is that some temperature due to VISCOUS DISSIPATION at the high rotating speed, or more friction loss?

Many thanks
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Old   April 30, 2018, 23:07
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You can calculate how much the heat is due to the rotation is from the wall shear stress and rotation speed and compare it to the temperature rise that you see.

But what is your thermal wall boundary condition? Is it a fixed heat flux?
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Old   May 4, 2018, 13:44
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Quote:
Originally Posted by LuckyTran View Post
You can calculate how much the heat is due to the rotation is from the wall shear stress and rotation speed and compare it to the temperature rise that you see.

But what is your thermal wall boundary condition? Is it a fixed heat flux?
Thank you for your reply.
I set the constant power(500 w) in the main body, and the external surface of the shaft is modeled as an adiabatic boundary condition. On this basis, all the heat is dissipated to the coolant through a forced convection between the shaft’s internal surface and the fluid. My prediction is that the flow temperature rise should be same.

But i found that the higher speed, the higher rise of temperature .My curiosity is that where is the extra loss? Is it from the wall shear stress? or in another word, from the wall friction losses? Can CFD calculate it ? where to see it.

Or the extra temperature rise is due to my model fault.
Cheers
Gary
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frictional viscosity, rotating fluids, temparature, viscous dissipation

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