Influence of G-Jitters on Thermodiffusion in a Ternary Mixture: Comparison between Onboard ISS and FOTON Platforms
- Paper number
IAC-05-A2.6.03
- Author
Dr. Yu Yan, Ryerson University, Canada
- Coauthor
Prof. Ziad Saghir, Ryerson University, Canada
- Coauthor
Dr. M. Chacha, UAE University, Faculty of Engineering, United Arab Emirates
- Year
2005
- Abstract
The phenomenon of mass flux in a mixture driven by a temperature gradient is known as thermodiffusion or the Soret effect. This effect is usually small compared to the molecular diffusion but can be quite significant in the analysis of compositional variation in hydrocarbon reservoirs. Accurate experimental and theoretical models are essential for better understanding and quantification for effective characterisation of situations involving these coupled processes. This requires precise knowledge of the transport coefficients particularly the Fick and Soret diffusion coefficients. Unfortunately, measurements of the Soret coefficient under the terrestrial conditions reveal a great complexity due to the strong gravity induced convection. One possible remedy is to minimize the buoyancy by performing experiments under microgravity on free flying platforms, such as the International Space Station (ISS) and FOTON. Without the buoyancy-induced convection, experiments under such conditions may lead to accurate measurement of the Soret coefficient. However, virtually all space laboratories experience undesirable steady and/or oscillatory residual accelerations (g-jitters) caused by the movement of the crew and operation of onboard equipments. The existence of the g-jitter does induce a convection motion and affect the accuracy of the measurement. It is therefore important to analyze the effect of the g-jitter on diffusion processes for a better interpretation of the experimental results from the space laboratories. In this paper, we study the effect of g-jitters encountered onboard the ISS and FOTON on the mass-thermo-fluid dynamics in the presence of Soret effect. The system under investigation consists of a rectangular cavity saturated with a ternary mixture of normal butane, dodecane and methane (0.2/0.3/0.5 mole fraction) subject to a lateral temperature gradient. The three-dimensional full transient Navier-Stocks equations, coupled with energy and mass transfer equations are solved numerically using the control volume method [1]. The viscosity and the mass density of the fluid mixture, as well as the thermodiffusion coefficients are calculated from theoretical models as functions of the actual local temperature, pressure and composition [2, 3]. G-jitters in the ISS and FOTON platforms are represented by a Fourier Series with the coefficients derived from the actual experimental data acquired during space mission ISS and FOTON-12 [4]. Various scenarios are studied in terms of the crew status, spacecraft attitude, sensor locations etc. Preliminary results analyses show that normal-butane and methane segregate towards the hot wall while dodecane migrates towards the cold end of the cavity. The mass differentiation of the mixture components are affected by factors such as the alignment of the cavity with the direction of the g-jitter. Comparison between the modelled results using both the ISS and FOTON data are made to discover unique features of both platforms in thermodiffusion experiments. Reference: [1]Patankar, S. V., 1980, (New York: McGraw-Hill). [2]Lohrenz, J., Bray, B. G., and Clark, C., 1964, 1171. [3]Firoozabadi, A., Ghorayeb, K., and Shukla, K., 2000, 46(5), 892. [4]Shevtsova,V., Melnikov, D. and Legros, J.C., 1999, (ESA Report).
- Abstract document
- Manuscript document
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