[Back]

T. Loimer, J. Reznickova, P. Uchytil, K. Setnickova:
"Measurements on the flow of vapors near saturation through porous Vycor glass membranes";
Talk: 4th International Conference on Porous Media and its Applications in Science, Engineering and Industry, Potsdam; 2012-06-17 - 2012-06-22; in: "Porous Media and Its Applications in Science, Engineering, and Industry: Fourth International Conference", K. Vafai (ed.); AIP Conference Proceedings, 1453 (2012), ISBN: 978-0-7354-1053-4; 97 - 102.

We present experimental data of the flow of butane and isobutane vapors through porous Vycor glass membranes. The pressure driven flow of vapors near and far from saturation through membranes with pore diameters of 20 and 33 nm is investigated. The upstream pressures lie between the saturation pressure at the upstream temperature to approximately half that value. The pressure differences are between a few kPa to about 100 kPa. From an adiabatic description of the flow process, we expect condensation of a vapor close enough to saturation and hence, due to the action of capillary forces, an increase in mass flux with respect to the mass flux of a vapor that remains in a gaseous state. According to the adiabatic description, a vapor that flows through a porous membrane may condense for two reason: One reason is capillary condensation in the pores of the membrane, the second reason is heat conduction from the upstream to the downstream side of the membrane due to the Joule-Thomson effect. If the flux of heat in downstream direction is large enough, a vapor near saturation at the upstream side of the membrane may only release sufficient heat by condensation. Describing the flow in terms of dimensionless groups recovered from an adiabatic description of the flow process, we find that a vapor condenses and the mass flux is increased if (i) a dimensionless permeability of the membrane is larger than one and (ii) if the vapor at the upstream side is close enough to saturation such that a dimensionless group involving the upstream pressure and the pressure difference is also larger than one. Experimental data corroborates condition (i) above and indicates that condition (ii) might be valid.

http://dx.doi.org/10.1063/1.4711159

http://publik.tuwien.ac.at/files/PubDat_208076.pdf