Towards a predictive evaporation model for multi-component hydrocarbon droplets at all pressure conditions |
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| Authors: | V Ebrahimian C Habchi |
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| Affiliation: | 1. Chair of Numerical Thermo-Fluid Dynamics, Department of Energy Process Engineering and Chemical Engineering, Technische Universität (TU) Bergakademie Freiberg, Germany;2. Department of Energy Process Engineering and Chemical Engineering, Technische Universität (TU) Bergakademie Freiberg, Germany;1. Sir Harry Ricardo Laboratories, Centre for Automotive Engineering, School of Computing, Engineering and Mathematics, Faculty of Science and Engineering, University of Brighton, Brighton BN2 4GJ, UK;2. Chuiko Institute of Surface Chemistry, 17 General Naumov Street, Kiev 03164, Ukraine;3. Clean Combustion Research Centre, Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia;4. Université de Lorraine, LEMTA, UMR 7563, Vandoeuvre-lès-Nancy, France;5. CNRS, LEMTA, UMR 7563, Vandoeuvre-lès-Nancy, France;6. INSA-Rouen, UMR-CNRS 6614, CORIA, BP 8, 76801 Saint Etienne du Rouvray Cedex, France;1. Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600036, India;2. Department of Mechanical and Industrial Engineering, University of Minnesota Duluth, Duluth, MN 55812-3042, USA;3. Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588-0526, USA;1. Central Research Institute of Electric Power Industry (CRIEPI), 2-6-1 Nagasaka, Yokosuka, Kanagawa 240-0196, Japan;2. College of Industrial Technology, Nihon University, 1-2-1 Izumi-cho, Narashino, Chiba 275-8575, Japan |
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| Abstract: | In this paper, a new evaporation model for multi-component hydrocarbon droplets is proposed. Compared to previously published models, it has two new features. First, an expression of the Stefan velocity is proposed which ensures gas mass conservation. In addition, the evaporation rate of each species is obtained by the integration of the exact equation of species mass fraction. Second, the heat flux due to species diffusion is taken into account in addition to the classical conduction heat flux between the gas and the liquid droplets. The comprehensive multi-component droplets vaporization model including the above two features is presented for high and low pressure conditions, for which a real and a perfect fluid equation of state (EOS) has been used, respectively. Free convection is also taken into account using the Grashof number in the Kulmala–Vesala correlations 1] for the Sherwood and Nusselt numbers. The model is compared with very accurate experimental data which were recently obtained by Chauveau et al. (2008) 2] at atmospheric pressure and temperature ranges of 473–973 K for n-heptane and 548–623 K for n-decane droplets of 400 μm initial size. A very good agreement with the experimental data including micro-gravity conditions has been obtained. Indeed, the results have confirmed that the free convection process plays a significant role in the evaporation rate of liquid droplets under earth gravity and quiescent conditions. This shows the relevance of the new features of the model. The numerical results have also shown that real fluid EOS is not necessary at atmospheric pressure for the temperature range given above. In addition, the numerical results of the new model are also compared with the experimental data of Birouk (1996) 3] for two-component droplets of n-heptane and n-decane with different compositions of the liquid mixture. Finally, the non-ideality of the mixture is shown to become significant at high ambient pressures and especially at low ambient temperature conditions where a real-gas EOS is needed. |
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