Abstract
Phase equilibria of fluid mixtures are important in numerous industrial applications and are, thus, a major focus of thermophysical property research. Improved data, particularly along the dew line, are needed to improve model predictions. Here we present experimental results utilizing highly accurate densimetry to quantify the effects of sorption and capillary condensation, which exert a distorting influence on measured properties near the dew line. We investigate the (pressure, density, temperature, composition) behaviour of binary (CH4 + C3H8) and (Ar + CO2) mixtures over the temperature range from (248.15 to 273.15) K starting at low pressures and increasing in pressure towards the dew point along isotherms. Three distinct regions are observed: (1) minor sorption effects in micropores at low pressures; (2) capillary condensation followed by wetting in macro-scale surface scratches beginning approximately 2% below the dew-point pressure; (3) bulk condensation. We hypothesize that the true dew point lies within the second region.
Highlights
Thermophysical property measurements in the vicinity of the dew line of fluid mixtures can be substantially distorted by sorption and condensation effects
When studying the vapour phase, experimenters often avoid regions being affected by sorption effects or just ignore the distorting impact, which means that inevitable systematic errors are introduced
The current work is the launch of a comprehensive project that aims to combine the well-established fields of density measurement and sorption phenomena with a novel approach
Summary
Thermophysical property measurements in the vicinity of the dew line of fluid mixtures can be substantially distorted by sorption and condensation effects This is due to the preferential sorption or condensation of one or more component(s), which changes the vapour composition from that originally loaded into the measuring cell of an experimental apparatus. Kleinrahm and Wagner[2] in the early 1980s developed a technique to cancel out sorption effects in the measurement of gas densities Their method equalized the surface area of the www.nature.com/scientificreports/. May et al.[8] measured densities and dew points of light hydrocarbon mixtures, and their work has the most in common with our current study For their measurements, May et al modified a commercial gravimetric sorption analyser (incorporating a magnetic suspension coupling), which is designed to simultaneously measure sorption and density. When studying the vapour phase, experimenters often avoid regions being affected by sorption effects or (more commonly) just ignore the distorting impact, which means that inevitable systematic errors are introduced
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