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-   -   Vortex tube Stimulation in solid works (http://www.cfd-online.com/Forums/floefd-floworks-flotherm/97736-vortex-tube-stimulation-solid-works.html)

tsram90 February 23, 2012 11:56

Vortex tube Stimulation in solid works
 
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.

http://www.cfd-online.com/Forums/att...ortex-tube.jpg

tim_shute February 27, 2012 22:15

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

tsram90 February 27, 2012 23:21

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.

Boris_M February 29, 2012 10:23

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

tsram90 February 29, 2012 10:45

Quote:

Originally Posted by Boris_M (Post 346905)
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.

Boris_M February 29, 2012 10:55

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

lihui54312 April 11, 2012 23:38

Quote:

Originally Posted by Boris_M (Post 346910)
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.

pcaste12 June 1, 2012 12:06

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.

tsram90 June 1, 2012 13:09

Quote:

Originally Posted by pcaste12 (Post 364306)
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.

pcaste12 June 1, 2012 13:14

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..)?

tsram90 June 1, 2012 23:50

Quote:

Originally Posted by pcaste12 (Post 364326)
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.

pcaste12 June 2, 2012 03:53

Many thanks for the advise :)

areej2014 March 5, 2014 13:16

hi,
can u help me by sending me the steps to draw this vortex tube at fluent

tsram90 March 7, 2014 11:12

It is better to draw the body in soft wares like solidworks, catia etc and import it to fluent.

zain rafaqat April 24, 2014 19:13

vortex tube analysis
 
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

tsram90 April 27, 2014 14:34

Quote:

Originally Posted by zain rafaqat (Post 488065)
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.

zain rafaqat April 29, 2014 16:24

voretx tube
 
1 Attachment(s)
Quote:

Originally Posted by Boris_M (Post 346905)
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

Boris_M May 5, 2014 05:11

Hello Zain,

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

Boris

zain rafaqat May 5, 2014 16:11

..................
 
..or in solidworks...or where could i find..?

Boris_M May 6, 2014 11:54

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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