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 rskrishna87 January 26, 2011 10:55

Steps for analysis of a flow

Hi guys,

I am very new to CFX modeling so hello fellos.

And right now i am using ANSYS Workbench 13.0 to model a gas flow of a impingement plate with neumann boundary conditions and varying the design

I have a gas flow that is running through an impingement jet(from top to bottom) with a diameter of 0.0006(set as one of the design parameter) and a length of 0.00425(from top to bottom) with a static pressure of 1.95kPa and Static Temperature of 450°C at the top(colder side) and 1250°C at the bottom surface(hotter side).
I have the results of simulations for different design variations(like platedepth,inlet,outlet diameter)
So can anyone suggest me few steps that are generally done in a flow process analysis?

Krishna:)

 ghorrocks January 26, 2011 19:29

Do the CFX tutorials, they are a good start. Have a look at the tutorials on the CFX-Community website as well. Do a literature search for similar applications to get a feel for how other people have done this sort of model.

 rskrishna87 January 27, 2011 04:46

Shear stress transport model

I am using a shear stress transport model...so for solving the problem theoretically what kind of equations do i have to solve??

 ghorrocks January 27, 2011 17:20

What do you mean"theoretically"?

 rskrishna87 January 28, 2011 06:20

theoretically how to predict the Cooling efficiency??

The thing is i have all the post process results...including heat flux and heat transfer coefficient and Reynolds number and the give ngeometrical and fluid parameters...Can you tell me theoretically how to predict the Cooling efficiency

 ghorrocks January 28, 2011 06:32

You have the parameters from your simulation so you can work out the cooling performance from that. Or are you asking what is the expected cooling efficiency? In that case go to any heat transfer textbook and they should cover heat transfer from impinging jets.

 rskrishna87 January 28, 2011 07:35

yup thanks man...experimentally i can figure out the cooling efficiency ...But theoretically i need to know the expected cooling efficiency..Can you please tell me which text book is good for that.

Thanks,

Krishna

 ghorrocks January 28, 2011 08:03

I go back to my original question - what do you mean by "theoretically"? I do not know of any theory which will tell me this, only empirical models and simulation results.

 rskrishna87 January 28, 2011 10:14

Ok i am really sorry....can u please tell me how to experimentally determine the Cooling efficiency of a SST model with Thermal energy conditions as i said above using the post processing simulation results of CFX?...the last time i typed the message i have typed it by mistake..sry

 ghorrocks January 28, 2011 16:19

Nothing to be sorry about, it just seems you don't know what some of the terms you are using mean and imply. Here's some definitions:

Simulation = a numerical model of a physical process
Numerical Model = an approx answer to an analytical mathematical model of a physical process
Experiment = Measurements of a physical process
Empirical Model = A curve fit onto experimental results, with no reference to the underlying theory of the process.
Theoretical model = A mathematical model which describes the underlying physical process

In complex flows like impinging jets you usually only get empirical models and simulation results. Both are only approximations.

So is your question - Are you trying to measure the modelled heat transfer from a impinging jet simulation?

 rskrishna87 January 29, 2011 11:50

hi,

yes exactly...so let mw know how to do this please...thaks:)

 ghorrocks January 30, 2011 05:35

OK, now that I know what you are asking I can answer you :)

Easy: areaInt(Wall Heat Flux)@Surface should do it. Either put this CEL expression on a monitor point or in the CFD-Post function calculator for post-processing.

 rskrishna87 January 31, 2011 05:13

Thanks you man,

It was bugging me since a week.Now I will try it tomorrow.Since i am outside today and do not have access to work.:)

And one more thing is this gives me the heat flux at any point right. And mine is a thermal energy transfer SST model. So is there anything like Is entropic efficiency or anything that i can find??

 ghorrocks January 31, 2011 07:21

Quote:
 this gives me the heat flux at any point right.
No. Read the documentation - the function I gave integrates the Wall Heat Flux over the wall boundary called "Surface 1".

Define a CEL expression for the entropic efficiency, that's all you need do.

 rskrishna87 February 1, 2011 09:23

entropic efficiency?

does anyone know the expresion for the entropic efficiency in CFD Post?

 rskrishna87 February 1, 2011 12:08

I have one more question...Mine is a heat exhanger.. with impinging jets...So does anyone know hwo do you calculate the cooling efficiency using mass flow, Specific heat,Temperature ,pressure ??

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