Finding Outlet Diameter for Compressible Fluid Flow

[johnmane]

hii ,
i know the inlet conditions i.e. dia 2mm , pressure = 100 bar, density= 0.001176 m3/kg, mass flow rate remains constant= 0.09017 m/s , for same mass flow rate for pressure drop 80 bar(i.e. pressure at outlet is 20 bar) for COMPRESSIBLE FLUID what will be the outlet dia? take fluid carbon dioxide...

 

[Thaakisfox]

Use the Bernoulli equation, and continuity equation ;)

 

[ravijha]

no u can't use bernouli equation for a compressible fluid...use steady flow energy equations

 

[stewartcs]

no u can't use bernouli equation for a compressible fluid...use steady flow energy equations

Depends on what level of accuracy you want. The general rule of thumb is that if the pressure drop is less than 10% of the inlet pressure, then reasonable result can be obtained.

CS

 

[Topher925]

no u can't use bernouli equation for a compressible fluid...

Yes you can.

Is this for a real application, or is this a textbook problem? It this is for a real application, geometry matters. Is this a nozzle, piping system, what?

 

[Thaakisfox]

Of course you can use the Bernoulli equation..., the Bernoulli equation says:

$$\frac{v^2}{2}+w+U=constant$$

Over one streamline if the flow is "general" (well, almost, fluid is barotropic, outer force field is conservative etc), and everywhere if the flow is irrotational.

Here w is the specific enthalpy, and U is the potential of the force field.
This can be applied to "any" fluid, compressible and incompressible alike...

 

[johnmane]

hiiiii thanks for ur help and sorry for late response,
Topher925 u may be right...this is real problem...
but i know only inlet conditions ...don't know the outlet conditions...then how to apply this equation? if assumed outlet dia, then i am able to calculate velocity at outlet...but again one parameter misssing that is specific volume...actually this real problem came while analysing the expansion valve for carbon dioxide...