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An all-pressure fluid drop model applied to a binary mixture: heptane in nitrogen

Harstad, K. and Bellan, J. (2000) An all-pressure fluid drop model applied to a binary mixture: heptane in nitrogen. International Journal of Multiphase Flow, 26 (10). pp. 1675-1706. ISSN 0301-9322. http://resolver.caltech.edu/CaltechAUTHORS:20171019-111417758

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Abstract

The differences between subcritical liquid drop and supercritical fluid drop behavior are shown to be a direct consequence of the length scales near the fluid drop boundary. Under subcritical, evaporative high emission rate conditions, a film layer is present in the inner part of the drop surface which contributes to the unique determination of the boundary conditions; it is this film layer in conjunction with evaporation which gives to the solution its convective–diffusive character. In contrast, under supercritical conditions the boundary conditions contain a degree of arbitrariness due to the absence of a physical surface, and the solution has then a purely diffusive character. Results from simulations of a free fluid drop under no-gravity conditions are compared to microgravity experimental data from suspended, large drop experiments at high, low and intermediary temperatures and in a range of pressures encompassing the sub- and supercritical regime. Despite the difference between the conditions of the simulations and the experiments, the time rate of variation of the drop diameter square is remarkably well predicted in the linear curve regime. Consistent with the optical measurements, in the simulations the drop diameter is determined from the location of the maximum density gradient. Detailed time-wise comparisons between simulations and data show that this location is very well predicted at 0.1 MPa. As the pressure increases, the data and simulations agreement becomes good to fair, and the possible reasons for this discrepancy are discussed. Simulations are further conducted for a small drop, such as that encountered in practical applications, over a wide range of specified, constant far field pressures. Additionally, a transient pressure simulation crossing the critical point is also conducted. Results from these simulations are analyzed and major differences between the sub- and supercritical behavior are explained. In particular, it is shown that the classical calculation of the Lewis number gives erroneous results at supercritical conditions, and that an effective Lewis number previously defined gives correct estimates of the length scales for heat and mass transfer at all pressures.


Item Type:Article
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https://doi.org/10.1016/S0301-9322(99)00108-1DOIArticle
http://www.sciencedirect.com/science/article/pii/S0301932299001081?via%3DihubPublisherArticle
Additional Information:© 2000 Elsevier Science Ltd. Received 19 May 1999, Revised 20 October 1999, Available online 23 June 2000. This research was conducted at the Jet Propulsion Laboratory under sponsorship from the National Aeronautics and Space Administration, the Lewis Research Center with Dr. Daniel L. Bulzan as technical contract monitor. His continuing interest and support are greatly appreciated. We also want to thank Prof. Hiroshi Nomura of Nihon University in Chiba, Japan, and Prof. Iskender Gökalp of the Centre National de la Recherche Scientifique in Orléans, France, for providing us with their data.
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Funding AgencyGrant Number
NASA/JPLUNSPECIFIED
Subject Keywords:Supercritical/subcritical fluid drops
Record Number:CaltechAUTHORS:20171019-111417758
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20171019-111417758
Official Citation:K Harstad, J Bellan, An all-pressure fluid drop model applied to a binary mixture: heptane in nitrogen, In International Journal of Multiphase Flow, Volume 26, Issue 10, 2000, Pages 1675-1706, ISSN 0301-9322, https://doi.org/10.1016/S0301-9322(99)00108-1. (http://www.sciencedirect.com/science/article/pii/S0301932299001081)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:82498
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:19 Oct 2017 18:18
Last Modified:19 Oct 2017 18:18

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