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February 12, 2020, 11:10 |
How to increae diffusion in flow?
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#1 |
Member
Abdullah Arslan
Join Date: Apr 2019
Posts: 94
Rep Power: 7 |
Good day,
Can we increase diffusion in a fluid flow, say by Lewis number (if there is any option)? My flow is laminar with thermal energy on. I don't want to change either density, heat capacity or thermal conductivity. I am using also real gas mixture from library. The reason I want to increase it, just to see its effect without changing the 3 mentioned parameters. Regards |
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February 12, 2020, 12:02 |
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#2 |
Senior Member
Gert-Jan
Join Date: Oct 2012
Location: Europe
Posts: 1,827
Rep Power: 27 |
Diffusion is for molecules. So, if you have a massfaction equation for a component that you want to diffuse in the continuous phase, than you can add a kinematic diffusion coefficient in the tab Fluid Models/Component Models.
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February 12, 2020, 15:06 |
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#3 |
Senior Member
Join Date: Jun 2009
Posts: 1,804
Rep Power: 32 |
May I ask what you mean by diffusion?
Momentum diffusion is through molecular viscosity, mu Thermal diffusion is through thermal conductivity, k Mass diffusion is through mass diffusivity, density * D, where D is the kinematic Diffusivity What are you trying to achieve? Lewis number is the ratio of thermal diffusion to mass diffusion, i.e. Le = [k/(rho Cp) ] / D which relates the energy equation respect to the mass diffusion equations. Similarly, you can use the Schmidt number as the ration between momentum diffusion, and mass diffusion, i.e. Sc = mu / (rho D) which diffusion are you trying to modify or study? As you can see, there are 5 parameters so far: Density, rho Specific Heat, Cp Thermal Conductivity, k Dynamic Viscosity, mu Kinematic Diffusivity, D and you want to fix the first 3, you are only left with changing viscosity and kinematic diffusivity. I would fix the viscosity, vary the Schmidt number and compute the corresponding input kinematic diffusivity, D = Dynamic Viscosity / Density / Schmidt Number Hope the above helps,
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