Solutal thermodiffusion in binary mixture in the presence of g-jitter

• Published in: International journal of thermal sciences Vol. 41; no. 10; pp. 899 - 911
• Main Authors: Chacha, M., Faruque, D., Saghir, M.Z., Legros, J.C.
• Format: Journal Article
• Language: English
• Published: Paris Elsevier Masson SAS 01.10.2002; Elsevier
• Subjects: Convection and heat transfer; Density calculation; Exact sciences and technology; Fluid dynamics; Fundamental areas of phenomenology (including applications); g-jitter; Micro-gravity; Numerical simulation; Physics; Soret effect; Turbulent flows, convection, and heat transfer; Soret effect; Micro-gravity; Numerical simulation; g-jitter; Density calculation; Finite element method; Temperature distribution; Thermohaline convection; Digital simulation; Heat mass transfer; Jitter; Natural convection; Density distribution; Binary mixtures; Microgravity; Concentration distribution; Double diffusion
• ISSN: 1290-0729; 1778-4166
• DOI: 10.1016/S1290-0729(02)01382-0

The phenomenon of mass flux in a mixture due to a temperature gradient is known as the Soret effect or thermal diffusion. This effect is usually small but can be quite important in the analysis of compositional variation in hydrocarbon reservoirs. Diffusion-dominated experiments on-board the International Space Station will be greatly affected by convective flow due to the residual acceleration field and/or to oscillatory g-jitters caused by several sources. In this paper we are interested in investigating the flow due to thermal diffusion for different oscillatory g-jitters. The model considered is a rectangular rigid cavity filled with a binary mixture of methane and normal butane, subject to a temperature difference on its end walls and radiation heat transfer on the lateral ones. The non-linear differential equations for the mass-thermo-vibrational problem are derived in the case of a unique mode oscillatory acceleration. The full transient Navier–Stokes equations coupled with the mass and heat transfer formulations and the equation of state of the fluid are solved numerically using the finite element technique. Results revealed that the thermal diffusion is important and drives a strong convection. Convection is enhanced and therefore temperature and species profiles distortion from purely diffusive condition increases when a parallel g-jitter is added to the residual gravity, in a destabilizing configuration. The numerical study shows that both residual gravity and g-jitter may be detrimental but also beneficial to achieve purely diffusive conditions, according to the orientation of the vibration direction and the residual gravity vector, relative to the direction of the main density gradient. For the different configurations investigated, the g-jitter is found to reduce compositional variation. When the stable regime is attained, thermal and compositional quantities fluctuate following a mode whose frequency is equal to that of the initially imposed vibration. Even if the temperature fluctuation at a given point remains small, the compositional variation due to residual g-jitter convection is not negligible.