This seems largely correct but I must admit I have never seen an experiment that clearly demonstrates that diffusion is the main feature. Perhaps such experiments have been carried out but if so I think one would have to do something extremely challenging like filming the process at extremely high FPS rates with something like a scanning electron microscope. My sense is that the “performance curve” of filters is mostly empirically deduced while we are actually only extrapolating when making statements about what exactly causes these empirical results.
For example, another process I intuitively feel is different between air and water is the density and thus the force of the fluid on contaminants. If you travel in a boat, it is so much harder to stick your hand in the water compared to the air. Similarly, a particle that could potentially attach to a filter fiber in water is unlikely to stay attached as the water would exceed such a high force on it that it detaches. This is why one washes one’s car with a water hose, not an air hose.
I would be interested in any experiment that has looked at the micro scale physics involved in air filtration but my impression after looking at a lot of filter literature is that there are few, if any such studies.
Absolutely, if anything I trust decades of consistent, empirical results way more than something arrived at by armchair mathematics, or even worse, a mixture of intuition and extrapolated theories.
This seems largely correct but I must admit I have never seen an experiment that clearly demonstrates that diffusion is the main feature. Perhaps such experiments have been carried out but if so I think one would have to do something extremely challenging like filming the process at extremely high FPS rates with something like a scanning electron microscope. My sense is that the “performance curve” of filters is mostly empirically deduced while we are actually only extrapolating when making statements about what exactly causes these empirical results.
For example, another process I intuitively feel is different between air and water is the density and thus the force of the fluid on contaminants. If you travel in a boat, it is so much harder to stick your hand in the water compared to the air. Similarly, a particle that could potentially attach to a filter fiber in water is unlikely to stay attached as the water would exceed such a high force on it that it detaches. This is why one washes one’s car with a water hose, not an air hose.
I would be interested in any experiment that has looked at the micro scale physics involved in air filtration but my impression after looking at a lot of filter literature is that there are few, if any such studies.
While it’s nice to know the mechanism, I think all we really need in this case is the empirically determined performance curve.
Absolutely, if anything I trust decades of consistent, empirical results way more than something arrived at by armchair mathematics, or even worse, a mixture of intuition and extrapolated theories.