Whereas different models are commercially available for measuring the permeability of flat materials (such as textiles) to air, I am not convinced that the same equipments can do the same for porous monoliths. Can you recommend a device able to perform such measurements, NOT on thin materials or membranes (or not only !), but for blocks, and for which the sample preparation would be very simple ? Thanks !
In our laboratory, we have a permeater Cembureau, which allows to determine the gas permeability of porous material. We use it especially for concrete or other material in Civil Engineering, for cracked or sane materials. We apply a pressure gradient and then measure the gas flux, which is very low, but measurable.
Good question. We have built our own permeability test equipment based on a simple method: we put in a flange our sample (sealed with a suitable silicone rubber to avoid any gas leak at the circumference of the sample), then have on one side a container of known volume (including all tubes and valves) and have on the other side of the sample a valve, which is open to air (measure the air pressure!). After opening the valve, the pressure in the container increases. The pressure-time profile is recorded and evaluated with a simple but exact theory, which has as the only fit parameter the permeability (measured in m^2). That's it. We tested our equipment with sintered glass bodies and found out that the permeability is independent of the pressure difference between the container and the outside pressure as it should be. We measure porous bodies from monolithic aerogels to bonded sand beds. Porosity range 10^-15 to 10^-10 m^2. To optimize the mesurement, just have a few vessels of different size on the low pressure side. It works perfectly. The conventional ways using a pressure difference method or a constant flux etc etc. are in my opinion doubtful and difficult (measurement of a flow is more complicated than measuring of a pressure). In addition very low permeabilites like those of concrete are hard to mesure, since even for thn samples, one comes into a regime, where the non-linear permation equation has to be used. But maybe you can use for your purposes an equpment from Labthnk: http://www.labthink.com/en-us/product/tqd-g1-air-permeability-tester.html
I attach a document from our last summer school on aerogels, that describes also our equipment. Hope it is helpful.
Sorry for replying late, but the windows for replying remained inactive for several days, I don't know why.
Thank you for your interesting answers.
Unfortunately, I have no workshop for building a lab-made permeameter, but I have a little budget for purchasing a commercial one.
I have seen the Labthink machine, but it seems to be suitable for flat materials only (what I wanted to avoid). At least, this is what I guess from the morphology of the sample holder. Am I wrong ? Moreover, there is no sensor of differential pressure measuring the pressure drop accross the sample, so are the results really reliable ?
@ Philippe: I am not aware of Cembureau permeater: can you provide more detail, please ?
Thanks one more
Alain
- Badges
- Science topic
- Similar topics
- Mathematical Sciences
- Statistics
- Probability
- Probability Theory
- Reliability