Maximizing Filtration With Rosedale's Unique “Y ... - Filtration News

same-size pores in adjacent layers.Thus, while the flow-average pore diameteris the same for all layers, in astack of those layers the distribution ofpore sizes is relatively narrow:Assuming 5 layers, the flow equationisThe cumulative plot of Equation 9 isLine F in Figure 1.The distribution of flow-pore diametersthrough a stack of layers is (obviously)narrower than through thesurface area, Line C in Figure 1.Questions that have not been answeredare: Do both faces of the Category-1media have the samepore-size distributions, via the ImageJmeasurements and the porometermeasurements?Measuring the viscous-flow averagedpore diameter through the depthof a real medium.Reaching this value begins withmeasuring the permeability, B(m2 ) ofthe filter medium, Equation 2.This diameter corresponds to thepore-size rating of the filter medium.Writers who tie the rating to a specificfiltration test fail to understand thatsuch a rating changes with changingconditions of a test, such as changes inthe test fluid, test particles, temperatureFNand fluid flow rate.The cumulative plot of Equation 8 isLine D in Figure 1.Assuming 10 layers, the flow equationisand where a plot of u vs. ΔP, on log/logpaper, is a straight line of slope 1.0, indicatingviscous (laminar) flow. At highdriving pressures the slope falls to 0.5in inertia flow.After determining the porosity of themedium, ε the ratio of void volume tobulk volume, calculate the flow-averagedpore diameter, d,Peter R. Johnston, PE is an editorial boardmember of International Filtration News.He can be reached byTel/Fax: 1 919 942 9092Email: ddandp3@aol.comwww.filtnews.com • June 2012 • 39