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Advances in droplet evaporation
KTH, School of Engineering Sciences (SCI), Mechanics, Physicochemical Fluid Mechanics.ORCID iD: 0000-0002-1095-118X
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Droplet evaporation (and condensation) is one of the most common instances of multiphase flow with phase change, encountered in nature as well as in technical applications. Examples include falling rain drops, fogs and mists, aerosol applications like electronic cigarettes and inhalation drug delivery, and engineering applications like spray combustion, spray wet scrubbing or gas absorption, spray drying, flame spray pyrolysis. Multiphase flow with phase change is a challenging topic due to the intertwined physical phenomena that govern its dynamics. Numerical simulation is a valuable tool that enables us to gain insight in the details of the physics, often in cases where experimental studies would be too expensive, impractical or limited. In the present work, the focus is on the evaporation of small spherical droplets. Simulation of the evaporation of a pure and two−component droplet, in a stagnant flow, with the inclusion of detailed thermodynamics and variable physical and transport properties, shows the importance of enthalpy transport by species diffusion in the thermal budget of the system, and allows the identification and characterization of evaporating regimes for an azeotropic droplet. A new method for the interface resolved numerical simulation of laminar and turbulent flows with a large number of spherical droplets that undergo evaporation or condensationon, based on the immersed boundary concept, is developed. Validation with experimental data of pure and two−component droplets evaporating in homogeneous isotropic turbulence is conducted. The method is employed for the direct numerical simulation of spray evaporation in a turbulent channel flow, whereby mechanisms of spray migration and turbulence modulation are revealed, and a scaling of the evaporation enhancement with the turbulence is found. The sensitivity of the zero-dimensional multicomponent droplet evaporation model, used for general purpose multiphase flow calculations, to its many model parameters is analysed by uncertainty quantification, providing useful guidelines for the design and operation of droplet evaporation experiments and simulations.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2019. , p. 41
Series
TRITA-SCI-FOU ; 53
National Category
Fluid Mechanics and Acoustics
Research subject
Engineering Mechanics
Identifiers
URN: urn:nbn:se:kth:diva-263228ISBN: 978-91-7873-361-3 (print)OAI: oai:DiVA.org:kth-263228DiVA, id: diva2:1367481
Public defence
2019-11-29, Kollegiesalen, Brinellvägen 8, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20191108

Available from: 2019-11-08 Created: 2019-11-04 Last updated: 2019-11-08Bibliographically approved
List of papers
1. A Numerical Study of Ethanol-Water Droplet Evaporation
Open this publication in new window or tab >>A Numerical Study of Ethanol-Water Droplet Evaporation
2018 (English)In: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 140, no 2, article id 021401Article in journal (Refereed) Published
Abstract [en]

The present effort focuses on detailed numerical modeling of the evaporation of an ethanol-water droplet. The model intends to capture all relevant details of the process: it includes species and heat transport in the liquid and gas phases, and detailed thermophysical and transport properties, varying with both temperature and composition. Special attention is reserved to the composition range near and below the ethanol/water azeotrope point at ambient pressure. For this case, a significant fraction of the droplet lifetime exhibits evaporation dynamics similar to those of a pure droplet. The results are analyzed, and model simplifications are examined. In particular, the assumptions of constant liquid properties, homogeneous liquid phase composition and no differential volatility may not be valid depending on the initial droplet temperature.

Place, publisher, year, edition, pages
American Society of Mechanical Engineers (ASME), 2018
Keywords
Ethanol, Evaporation, Liquids, Ambient pressures, Composition ranges, Droplet temperature, Ethanol/water azeotrope, Homogeneous liquids, Liquid and gas phasis, Liquid properties, Model simplification, Drops
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-216797 (URN)10.1115/1.4037753 (DOI)000426056200003 ()2-s2.0-85030701328 (Scopus ID)
Note

 QC 20171114

Available from: 2017-11-14 Created: 2017-11-14 Last updated: 2019-11-04Bibliographically approved
2. An Immersed Boundary Method for flows with evaporating droplets
Open this publication in new window or tab >>An Immersed Boundary Method for flows with evaporating droplets
2019 (English)In: International Journal of Heat and Mass Transfer, ISSN 0017-9310, E-ISSN 1879-2189, Vol. 143, article id 118563Article in journal (Refereed) Published
Abstract [en]

We present a new Immersed Boundary Method (IBM) for the interface resolved simulation of spherical droplet evaporation in gas flow. The method is based on the direct numerical simulation of the coupled momentum, energy and species transport in the gas phase, while the exchange of these quantities with the liquid phase is handled through global mass, energy and momentum balances for each droplet. This approach, applicable in the limit of small spherical droplets, allows for accurate and efficient phase coupling without direct solution of the liquid phase fields, thus saving computational cost. We provide validation results, showing that all the relevant physical phenomena and their interactions are correctly captured, both for laminar and turbulent gas flow. Test cases include fixed rate and free evaporation of a static droplet, displacement of a droplet by Stefan flow, and evaporation of a hydrocarbon droplet in homogeneous isotropic turbulence. The latter case is validated against experimental data, showing the feasibility of the method towards the treatment of conditions representative of real life spray fuel applications.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2019
Keywords
Spray, Fuel, Evaporation, Phase change, Immersed boundary, Multiphase, Direct numerical simulation
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-261933 (URN)10.1016/j.ijheatmasstransfer.2019.118563 (DOI)000487564400090 ()2-s2.0-85070927066 (Scopus ID)
Note

QC 20191015

Available from: 2019-10-15 Created: 2019-10-15 Last updated: 2019-11-04Bibliographically approved
3. Uncertainty quantification of multispecies droplet evaporation models
Open this publication in new window or tab >>Uncertainty quantification of multispecies droplet evaporation models
(English)Manuscript (preprint) (Other academic)
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-263221 (URN)
Note

QC 20191104

Available from: 2019-11-04 Created: 2019-11-04 Last updated: 2019-11-04Bibliographically approved
4. Direct numerical simulation of spray evaporation in hot turbulent channel flow
Open this publication in new window or tab >>Direct numerical simulation of spray evaporation in hot turbulent channel flow
(English)Manuscript (preprint) (Other academic)
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-263223 (URN)
Available from: 2019-11-04 Created: 2019-11-04 Last updated: 2019-11-04Bibliographically approved
5. Immersed boundary method for direct numerical simulation of multicomponent droplet evaporation
Open this publication in new window or tab >>Immersed boundary method for direct numerical simulation of multicomponent droplet evaporation
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-263225 (URN)
Note

QC 20191104

Available from: 2019-11-04 Created: 2019-11-04 Last updated: 2019-11-04Bibliographically approved

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1617181920212219 of 32
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