Compressible vs. Incompressible Flow Equations

[fonz]

As a private study I'm trying to figure out fluid dynamics applied to compressed air systems. Most of the material I am studying considers only incompressible fluid flow. From what I understand about the differences between compressible and incompressible flow in terms of the equations it only becomes significant when the mach number reaches about 0.3

In my systems I'm dealing with working pressures of no greater than 7 bar. Can apply standard equations to my calculations without having to compensate for changing densities due to pressure?

 

[boneh3ad]

That depends entirely on how fast the air may move in your system and the range of pressures you plan to operate in. You haven't really described anything in enough detail to know that.

 

[cjl]

At pressures of up to 7 bar, you could very easily have flow choking in places (in other words, locations in the flow where M = 1), so with the information provided, it's impossible to say whether incompressible equations will suffice or not for your purposes.