Volumetric Flow Of Airduct from 1 to 3?

[Thermo]

Hi!

If i have an airduct with a fan in it creating a volumetric flow V0 with the following construction:

V0

|

|----- V1

|

|-----V2

|

V3

Where the airduct branches into 3 sections.

The friction of the airduct is known and the loss coefficient is 0. Also, the pressure before the fan is 1bar and so is the pressure after V1,V2, and V3. The diameters and lengths of the duct sections are known and the density of the air is 1.2.

How can i calculate V1, V2 and V3?

PS sorry for the crappy english =)

Edited April 16, 2012 by Thermo

[CaptainPanic]

Hello, welcome to the forum.

 

When you write "the diameters and lengths of the duct sections are known", can you give any more information about that?

What would be a good general formula to use in this case?

 

Note, this is our homework section - we make you work yourself, we do not give answers straight away.

[Thermo]

Hello, welcome to the forum.

 

When you write "the diameters and lengths of the duct sections are known", can you give any more information about that?

What would be a good general formula to use in this case?

 

Note, this is our homework section - we make you work yourself, we do not give answers straight away.

 

Hi!

 

Yes, i have the circumference and lengths of all sections. All the sections have the same circumference.

I did not include specific values in the description since i do not want people to solve it completely, but rather help me get started .

What i thought of was using bernoulli's equation, but the question is how? I have never done calculations for a system that splits before.

 

Trying to create an m-file in matlab for this allso. Will be working with it all day if i have to!

Edited April 17, 2012 by Thermo

[CaptainPanic]

Well, you can also create a mass balance. The total mass flow in is equal to the total flow out.

Since pressure and density are equal, your volumetric flows will be proportional to the mass flows, so we can say:

 

V0 = V1 + V2 + V3.

 

That in turn means you only need to know how the flow will divide itself (what is the relative flow in V1, in proportion to V2, and V3?). When you know the ratio of V1:V2:v3, you should arrive at your answer.

[Thermo]

Well, you can also create a mass balance. The total mass flow in is equal to the total flow out.

Since pressure and density are equal, your volumetric flows will be proportional to the mass flows, so we can say:

 

V0 = V1 + V2 + V3.

 

That in turn means you only need to know how the flow will divide itself (what is the relative flow in V1, in proportion to V2, and V3?). When you know the ratio of V1:V2:v3, you should arrive at your answer.

 

Thank you for your answer!

 

So basically, if i calculate all the losses (for V1, V2, V3) and then apply them on the formula so that V0=L1V1+L2V2+L3V3 i should have the proportional volumetric flows? I guess the first step is now to calculate all the separate loss for the different sections.

 

[messki678]

Hi!

If i have an airduct with a fan in it creating a volumetric flow V0 with the following construction:

V0

|

|----- V1

|

|-----V2

|

V3

Where the airduct branches into 3 sections.

The friction of the airduct is known and the loss coefficient is 0. Also, the pressure before the fan is 1bar and so is the pressure after V1,V2, and V3. The diameters and lengths of the duct sections are known and the density of the air is 1.2.

How can i calculate V1, V2 and V3?

PS sorry for the crappy english =)

 

dnt bother its okay.... we can understand that English is not your native language

[CaptainPanic]

Thank you for your answer!

 

So basically, if i calculate all the losses (for V1, V2, V3) and then apply them on the formula so that V0=L1V1+L2V2+L3V3 i should have the proportional volumetric flows? I guess the first step is now to calculate all the separate loss for the different sections.

What is L? (Or rather, what are L1, L2, L3)? And where do you think will be the losses? It sounds to me that there is no friction, so no losses?