- #1

tenichols94

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- TL;DR Summary
- When measuring pressure drop across a compressed air system the delta_P is different across the a component depending on the downstream flow path. I would like to know why, and how to quantify the energy loss across the component.

When measuring pressure drop across a compressed air system shown in the included figure, I get different results depending on the system downstream of the actual component I am measuring pressure drop across. Btw this is a real experiment that has been ran. The numbers below are different but a similar scenario is happening.

Case 1: The flow rate is 10 [cfm] and the pressure at P1= 63 and at P2=32 which gives us Delta_P1=31. So that would mean delta_P2 > 0.Case 2: The flow rate is 10 [cfm] and the pressure at P1= 70 and at P2=4 which gives us Delta_P1=66. Let's assume for this case the delta_P2 = ~0. So we can assume that the outlet is exposed to the atmosphere.To my knowledge for incompressible (fluid) systems the delta_P in at a given flow rate will be the same no matter the location in the system, which is why head loss charts can be so helpful in designing fluid systems. But as seen in this compressed air system the down stream head loss can have an affect on the pressure loss at the component that I want the measurement across.

Should the pressure loss be constant and my pressure gauges be read wrong?

Also, how can I quantify the energy loss in the system? At the inlet and outlet I have pressure, volumetric flow rate, and density at these points when making certain assumptions.

I want to use this experimental apparatus to help us understand which component flow better.

Case 1: The flow rate is 10 [cfm] and the pressure at P1= 63 and at P2=32 which gives us Delta_P1=31. So that would mean delta_P2 > 0.Case 2: The flow rate is 10 [cfm] and the pressure at P1= 70 and at P2=4 which gives us Delta_P1=66. Let's assume for this case the delta_P2 = ~0. So we can assume that the outlet is exposed to the atmosphere.To my knowledge for incompressible (fluid) systems the delta_P in at a given flow rate will be the same no matter the location in the system, which is why head loss charts can be so helpful in designing fluid systems. But as seen in this compressed air system the down stream head loss can have an affect on the pressure loss at the component that I want the measurement across.

Should the pressure loss be constant and my pressure gauges be read wrong?

Also, how can I quantify the energy loss in the system? At the inlet and outlet I have pressure, volumetric flow rate, and density at these points when making certain assumptions.

I want to use this experimental apparatus to help us understand which component flow better.