Effects of Temperature on Flow Rate

Using a pump we are cycling water through a capsule with filter media inside; while measuring the flow rate (l/min) and the pressure (psi) going in and the pressure going out. The water is cycled back into the same storage tank. As the flow rate increases the differential pressure should change linearly, which has been the case.

We have three separate sized canisters with the same filter media inside and each plot of Diff Pressure by flow rate has a R^2 over .995 for each trial we complete. The problem is that the slopes do not overlap as they should. We are adjusting the flow rate to a flux to ensure that the flow rates correspond to the same flux for each size. We believe that since we cannot regulate temperature (although we are monitoring it for each test) that the expansion of water, thus letting the density decrease is causing water to flow slightly faster and thus messing up our slopes, this is the case for even capsules of the same size since we are running trials in triplicate each capsule of the same size is even having a problem having slopes overlap.

We believe thermal expansion of the plastic and media is negligible since the greatest temperature change we observe is ~10*C.

How should we go about correcting for a temperature change in our flow/pressure?
 

Henryk

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If you measure the temperature of each test, then the pressure drop should be proportional to the product of flow rate Tims viscosity. Are you taking into account the different lengths and cross sections of the porous media? Are you familiar with the Ergun equation or Darcy's law for flow through porous media?
 

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