Compressed Air - Bernoulli Equation

In summary, the conversation revolves around understanding the dynamics of a compressed air system, specifically in terms of flow rate, air consumption, and pressure drop. The system consists of a 5.5 bar supply on 12mm OD Nylon Tubing, reduced to 6mm OD Nylon through a valve. The focus is on determining the flow through the 6mm section and the time it takes to fill a 10m section of pipe. The validity of using a simplified version of Bernoulli's principle is also questioned. The individual does not have a copy of Crane's TP 410 and has attached a PDF of their calculations for review. The main concern is whether accounting for flow turbulance, friction, and pressure drop will significantly affect
  • #1
fonz
151
5
I'm trying to ascertain the dynamics of a compressed air system in terms of flow rate, air consumption, pressure drop etc.

To keep it simple my system consists of a 5.5 bar supply (550000Pa) supply on 12mm OD Nylon Tubing and is reduced to 6mm OD Nylon through a valve (pressure drop assumed neglible for now) so the valve is treated as a simple orifice.

So I'm trying to work out the flow through the 6mm OD section (at 1 bar to start) after the valve opens. Then i want to work out how long it takes to fill up my 10m section of pipe (and actuator it is driving). If pressure drop is going to be an issue then i'd like to allow for it but i don't know how.

Also, in my calculations I used a simplified version of Bernoulli's principle. This I am told only applies to incompressible fluids or gases moving at velocities low than the speed of sound. So how valid are my calculations and do I have to alter them?

And no i don't have a copy of Crane's TP 410 :smile:

I have attached a PDF copy of my calc i did in Mathcad, if you can spot any errors please let me know.

Regards
Dan
 

Attachments

  • Compressed Air System Calc.pdf
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  • #2
Basically all i need to know is if my actual flow rate i calculated - 0.03m3/s (1800litres/min) is going to change by more than 50 litres/min if i account for flow turbulance/friction/pressure drop etc. I don't need to crunch some serious numbers, just roughly.
 

Related to Compressed Air - Bernoulli Equation

1. What is the Bernoulli Equation and how does it relate to compressed air?

The Bernoulli Equation is a fundamental equation in fluid mechanics that describes the relationship between fluid velocity, pressure, and potential energy. In the context of compressed air, it explains how the velocity of air increases as it flows through a constricted space, causing a decrease in pressure. This principle is used in systems such as air compressors and pneumatic tools.

2. How does the size of a nozzle affect the velocity and pressure of compressed air?

The size of a nozzle has a significant impact on the velocity and pressure of compressed air. According to the Bernoulli Equation, as the cross-sectional area of a nozzle decreases, the air velocity increases, causing a decrease in pressure. This is why smaller nozzles are used for applications that require high velocity, such as sandblasting, while larger nozzles are used for lower velocity applications like spray painting.

3. Can the Bernoulli Equation be used to calculate the flow rate of compressed air?

Yes, the Bernoulli Equation can be used to calculate the flow rate of compressed air. By measuring the pressure and velocity at different points in the system, the equation can be rearranged to solve for the flow rate. However, this calculation assumes ideal conditions and may not account for factors such as friction and turbulence in the system.

4. How does the temperature of compressed air affect the Bernoulli Equation?

The Bernoulli Equation assumes that the fluid is incompressible and that there is no change in temperature. However, in real-world applications, compressed air can experience changes in temperature due to adiabatic compression. This can affect the density of the air, which in turn can impact the results of the Bernoulli Equation calculation.

5. What are some practical applications of the Bernoulli Equation in compressed air systems?

The Bernoulli Equation has many practical applications in compressed air systems. It is used to design and optimize air compressors, determine the appropriate nozzle size for a given application, and calculate the flow rate and pressure drop in a system. It is also used in industries such as aerospace and automotive to design efficient airfoils and intake systems. Additionally, the principle of the Bernoulli Equation is used in devices like carburetors and atomizers to mix air and fuel for combustion engines.

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