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Vortex tube Stimulation in solid works

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Old   February 23, 2012, 11:56
Default Vortex tube Stimulation in solid works
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Solidworks Flow express and flow stimulation doesn't have any separate forums so I don't know where to post this.

Hello, I am stimulating working of a vortex tube using Solidworks Flow stimulation. Can someone help me with setting the Boundary Conditions?? I am not sure what boundary condition should I give for inlet and outlets

For Inlet should I give total pressure or static pressure? Or Should it be mass flow or any other?
I have air at 6 bar flowing in through it.

What should be the outlet? the outlets are open to atmosphere and air flows out at atmospheric pressure.

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Old   February 27, 2012, 22:15
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Tim Shute
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As I've learnt so far, I would suggest BCs setting are:
Inlet=Mass flow rate/volume flow rate/velocity;
Outlets= Environment Pressure 1atm
You could also simulate the heat exchange by input thermodynamics parameter if you need to know heat transfer and know relevant data.

The Inlet pressure could be regarded as a criteria to verify the simulation result. Although you could lengthen the cold outlet to relieve the vortex effect, What I am not sure is that if the result is reliable since there must be vortex crosses the openings in such a vortex tube. You could simulate the model first and then know if the cold outlet needs to be lengthened.

By the way, this model is axisymmetric. I dont think the vortex near the inlets will influence the flowing state; therefore set up a quarter of the model in Computational Domain (Periodic) would be timesaving.

Hope it could help.
Tim
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Old   February 27, 2012, 23:21
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Thank you. I will try some of these. Since i have some time, I think a will go with the full model.

When I give atmospheric pressure as outlet air is flowing from outlet back to the tube. I think I need to give a lower value there.
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Old   February 29, 2012, 10:23
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Boris Marovic
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Hi,
not quite right. I wouldn't use periodic boundary condition, this doesn't work as your flow is induced into a vortex going around in the cylinder, symmetry and periodicity is causing a counter flow at the plane where it is defined. It is like a mirror, if something coming towards it it is also coming towards it from the other side which you don't want to have.
And for the boundary conditions (BC) usually you know the total pressure on the inlets and use environment pressure on the outlet. The value of Environment pressure then is depending if it is entering the model (total) or leaving the model (static).

The difference of total and static is below:
P_total= P_static + P_dynamic + P_potential = P_static + 0.5*density*velocity^2 + density*gravity*height

So the total pressure includes the static plus the pressure due to height differences if gravity is considered and the kinetic pressure. For example if you consider a gas tank, the total pressure is pressure in the tank as the gas is at no velocity and the height can be considered zero in this simple case. so total pressure is for this steady state of a closed tank the same as static pressure in the tank. Now when opening the valve you'll still have the pressure inside the tank where you can say nothing is moving due to it's size but at the valve opening you'll have a high velocity plus a static pressure which in case of blowing into the atmosphere it will be atmospheric pressure and you can then say the velocity can be calculated from the total pressure you know is inside the tank is according to the formula the same as the static plus the dynamic and the static outside the tank (atmospheric pressure).
So if you have a gas canister or tank like a propane bottle it will be the total pressure of the gas tank.

Depending on the flow field it can be that the flow inside the cylinder is sucking into the cylinder but it shouldn’t suck into both sides at least not completely, there has to be a mass flow out of the cylinder.

Regards,
Boris
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Old   February 29, 2012, 10:45
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Quote:
Originally Posted by Boris_M View Post
Hi,
not quite right. I wouldn't use periodic boundary condition, this doesn't work as your flow is induced into a vortex going around in the cylinder, symmetry and periodicity is causing a counter flow at the plane where it is defined. It is like a mirror, if something coming towards it it is also coming towards it from the other side which you don't want to have.
And for the boundary conditions (BC) usually you know the total pressure on the inlets and use environment pressure on the outlet. The value of Environment pressure then is depending if it is entering the model (total) or leaving the model (static).

The difference of total and static is below:
P_total= P_static + P_dynamic + P_potential = P_static + 0.5*density*velocity^2 + density*gravity*height

So the total pressure includes the static plus the pressure due to height differences if gravity is considered and the kinetic pressure. For example if you consider a gas tank, the total pressure is pressure in the tank as the gas is at no velocity and the height can be considered zero in this simple case. so total pressure is for this steady state of a closed tank the same as static pressure in the tank. Now when opening the valve you'll still have the pressure inside the tank where you can say nothing is moving due to it's size but at the valve opening you'll have a high velocity plus a static pressure which in case of blowing into the atmosphere it will be atmospheric pressure and you can then say the velocity can be calculated from the total pressure you know is inside the tank is according to the formula the same as the static plus the dynamic and the static outside the tank (atmospheric pressure).
So if you have a gas canister or tank like a propane bottle it will be the total pressure of the gas tank.

Depending on the flow field it can be that the flow inside the cylinder is sucking into the cylinder but it shouldn’t suck into both sides at least not completely, there has to be a mass flow out of the cylinder.

Regards,
Boris
Thank you for the big long but very useful reply. After reading this I thought, whether we can define a very large area before the nozzles and give total pressure condition to it. Then when it enters the nozzle it can get converted to velocity and the required static pressure?

Another problem is if you define all inlet/outlets as pressure, the required mass flow rate cannot be obtained.

Similarly you cannot define all in terms of mass flow rate.
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Old   February 29, 2012, 10:55
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It should be generally possible to define all inlet and outlet openings as pressure as the pressure difference then defines the flow. That way you have specified enough data so the conservation of mass and the pressure can be calculated.

If you only define the mass flow for inlet an outlet you simply tell him what is necessary anyway but not enough to determine the pressure.

Sometimes it is better to define such a plenum but it should in general also work without.

Boris
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Old   April 11, 2012, 22:38
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Quote:
Originally Posted by Boris_M View Post
It should be generally possible to define all inlet and outlet openings as pressure as the pressure difference then defines the flow. That way you have specified enough data so the conservation of mass and the pressure can be calculated.

If you only define the mass flow for inlet an outlet you simply tell him what is necessary anyway but not enough to determine the pressure.

Sometimes it is better to define such a plenum but it should in general also work without.

Boris
Yes,you are right, but in this case, the best way defines the inlet as mass flow rate and the outlet as static pressure.
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Old   June 1, 2012, 11:06
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Hi,
Did you manage to make your simulation working on the vortex tube?
Inputing 6 bar inlet pressure and having a drop of temperature between inlet and cold outlet?

Many thanks for your answer.
Pierre.
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Old   June 1, 2012, 12:09
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Quote:
Originally Posted by pcaste12 View Post
Hi,
Did you manage to make your simulation working on the vortex tube?
Inputing 6 bar inlet pressure and having a drop of temperature between inlet and cold outlet?

Many thanks for your answer.
Pierre.

No I dropped it. I made a vortex tube and analyzed it.
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Old   June 1, 2012, 12:14
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You mean that you build you own vortex tube using materials and a compressor? If so, could I ask you which sort of tube you were using (copper, plexiglass, steel,etc..)?
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Old   June 1, 2012, 22:50
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Quote:
Originally Posted by pcaste12 View Post
You mean that you build you own vortex tube using materials and a compressor? If so, could I ask you which sort of tube you were using (copper, plexiglass, steel,etc..)?

I used a CPVC pipe. You know the one used in houses to take hot water. But if you can do it with Plexi glass it would be better because it would have less friction. Metal pipes absorb lot of heat and so are not recommended.
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Old   June 2, 2012, 02:53
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Many thanks for the advise
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Old   March 5, 2014, 13:16
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hi,
can u help me by sending me the steps to draw this vortex tube at fluent
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Old   March 7, 2014, 11:12
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It is better to draw the body in soft wares like solidworks, catia etc and import it to fluent.
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Old   April 24, 2014, 18:13
Default vortex tube analysis
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plz if.. you can post complete boundary condtions of vortex tube flow simuation in cfx....i am having trouble with this and not able to get temperature difference ,,,,streamlines bouncing back effect etc...plz help...? i have made 6 inlet vortex tube and is there any benefit of having inlet nozzles at some angle...if yes than what is optimuim angle for 6 inlets
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Old   April 27, 2014, 13:34
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Quote:
Originally Posted by zain rafaqat View Post
plz if.. you can post complete boundary condtions of vortex tube flow simuation in cfx....i am having trouble with this and not able to get temperature difference ,,,,streamlines bouncing back effect etc...plz help...? i have made 6 inlet vortex tube and is there any benefit of having inlet nozzles at some angle...if yes than what is optimuim angle for 6 inlets
Sorry I wasn't able to complete it till now.
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Old   April 29, 2014, 15:24
Default voretx tube
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Quote:
Originally Posted by Boris_M View Post
Hi,
not quite right. I wouldn't use periodic boundary condition, this doesn't work as your flow is induced into a vortex going around in the cylinder, symmetry and periodicity is causing a counter flow at the plane where it is defined. It is like a mirror, if something coming towards it it is also coming towards it from the other side which you don't want to have.
And for the boundary conditions (BC) usually you know the total pressure on the inlets and use environment pressure on the outlet. The value of Environment pressure then is depending if it is entering the model (total) or leaving the model (static).

The difference of total and static is below:
P_total= P_static + P_dynamic + P_potential = P_static + 0.5*density*velocity^2 + density*gravity*height

So the total pressure includes the static plus the pressure due to height differences if gravity is considered and the kinetic pressure. For example if you consider a gas tank, the total pressure is pressure in the tank as the gas is at no velocity and the height can be considered zero in this simple case. so total pressure is for this steady state of a closed tank the same as static pressure in the tank. Now when opening the valve you'll still have the pressure inside the tank where you can say nothing is moving due to it's size but at the valve opening you'll have a high velocity plus a static pressure which in case of blowing into the atmosphere it will be atmospheric pressure and you can then say the velocity can be calculated from the total pressure you know is inside the tank is according to the formula the same as the static plus the dynamic and the static outside the tank (atmospheric pressure).
So if you have a gas canister or tank like a propane bottle it will be the total pressure of the gas tank.

Depending on the flow field it can be that the flow inside the cylinder is sucking into the cylinder but it shouldn’t suck into both sides at least not completely, there has to be a mass flow out of the cylinder.

Regards,
Boris
.................................................. plz help plz if.. you can post complete boundary condtions of vortex tube flow simuation in cfx....i am having trouble with this and not able to get temperature difference ,,,,streamlines bouncing back effect etc...plz help...? i have made 6 inlet vortex tube and is there any benefit of having inlet nozzles at some angle...if yes than what is optimuim angle for 6 inlets..............or for solidworks..? im bit confused in defining boundary conditions in cfx as there or many options to concern....thank you in advance
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Old   May 5, 2014, 04:11
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Boris Marovic
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Hello Zain,

you are in the wrong part of the forum if you are looking for CFX help.

Boris
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Old   May 5, 2014, 15:11
Default ..................
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..or in solidworks...or where could i find..?
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Old   May 6, 2014, 10:54
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Maybe someone of the intial post can paste some real live like (not necessarily their own) BCs. That might help Zain.

Please? :-)

Thanks for your experts help this time ;-)
Boris
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