“Drying Droplets” - Formulation · drying and how it can be used to produce microstructured...
Transcript of “Drying Droplets” - Formulation · drying and how it can be used to produce microstructured...
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“Drying Droplets”
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Durham
Leeds Bristol
Sergii Veremieiev
Jonathan Reid
Colin Bain Phil Gaskell
Andrew Bayly Mark Wilson
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To develop a predictive understanding of dropletdrying and how it can be used to produce
microstructured particles and thin films both inmanufacturing processes and in end-use
applications.
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clipartfest.com
30 mm
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drops held in optical tweezers sequential printing of drops
Cira, Benusiglio & PrakashNature, 519, 446 (2015)
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spray drying
inkjet printing
crop spraying7
Atomiser
DriedPowder
DryingGas
SlurryDroplet
WetParticle
DriedParticle
wordpress.com
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Explore substrateheterogeneity
Mark Wilson
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Compare predictions withexperimental drop profiles
and internal flows
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Sampleof resultsfromJohnson(1997)
Finite difference modelling of rivulet formation oninclined planes, in lubrication approximation
Veremieiev
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Freedrops
Drops onsurfaces
Theory andmodelling
Processscale
WS1
WS2
WS3
WS4
CAPABILITIES
Methods &techniques
Singledrops
Interactions &coalescence
Scale-up &applications
Bain Reid Bayly GaskellWilson
Veremieiev
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* Centre for Process Innovation
* Procter and Gamble
* AkzoNobel
* Bristol Myers Squibb
* Merck
* Chiesi
* Aptuit
* Croda
* Syngenta
* Sun Chemical
* Inca Digital
* Nutricia
* Nestlé
* + accession mechanism for new companies
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U.K. Krieger, C. Marcolli and J.P. Reid, 'Exploring the Complexity of Aerosol Particle Propertiesand Processes using Single Particle Techniques‘, Chem. Soc. Rev. 41 (19) (2012) 6631 - 6662.
Optical Tweezers
• Indefinite trapping ofdroplets >1 mm radius.
• Manipulation of arrays.
• Characterisation ofwater content andtransport kinetics,viscosity, surfacetension,…
Gradient force:Pulling particles
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ElectrodynamicBalance (EDB)
• >4 mm radius liquiddroplets and solidparticles.
• Droplet size fromelastic light scatteringwith 10 ms time-resolution.
U.K. Krieger, C. Marcolli and J.P. Reid, 'Exploring the Complexity of Aerosol Particle Propertiesand Processes using Single Particle Techniques‘, Chem. Soc. Rev. 41 (19) (2012) 6631 - 6662.
Optical Tweezers
• Indefinite trapping ofdroplets >1 mm radius.
• Manipulation of arrays.
• Characterisation ofwater content andtransport kinetics,viscosity, surfacetension,…
Gradient force:Pulling particles
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Davies, Miles, Haddrell and Reid, ‘Influence of organic films on the evaporation and condensation of water inaerosol’, PNAS 110 (2013) 8807-88212.
• The evaporation coefficient falls below 1 × 10-4 when cetyl alcohol forms acomplete compact solid monolayer around the droplet surface.• The evaporation coefficient increases with decreasing carbon chain lengthand increase in temperature.
Suppressionof interfacialtransfer
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• Viscosity can be measured over more than 11 orders of magnitude (11 orders ofmagnitude in relaxation times) as a function of relative humidity/water activity.
• Droplet and bulk measurements are consistent although bulk measurements cannotaccess supersaturated states.
R. M. Power, S. H. Simpson, J. P. Reid* and A. J. Hudson 'The Transition from Liquid to Solid-LikeBehaviour in Ultrahigh Viscosity Aerosol Particles‘, Chemical Science 4(6) (2013) 2597 - 2604
Coalescence relaxation
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Water + 0.05%v 600-nmpolystyrene spheres, glass
Video speed x1/8
Particle tracks 2 – 3 s after impact
initial particle positionfinal particle position
~ 50 μm diameter dropletImpact velocity ~ 1 ms-1
Ambient temperature and humidity
20 μm
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Fluid σ / mNm-1 @ 20°C p / kPa @ 20°C
Ethanol 22.4 5.9
Isopropanol (IPA) 21.3 4.4
Methoxypropanol (PM) 27.7 @ 25°C 1.2
Water 72.9 2.3
Marangoni stresses drive internal flows tut ns h
¶¶= -
¶ ¶) )
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i. Particles uniformly dispersedii. Marangoni circulationiii. Particles migrate across streamlinesiv. Minimum radius of particle groupv. Marangoni flows stop and radial
flow carries particle to contact line
30%v IPA/water 0.1%v 600 nm PS, T= 20°C, RH 0.65
0.002 s 0.40 s 0.80 s 1.00 s 2.76 s
Scale 20μm
Video x 1/20
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Modelling of Spray Drying Process
Multiphase CFDModelling ofSpray Drying
Process
Droplet Drying ModelHeat/Mass Transfer, Size
and Morphological Changes
Particle-WallInteraction Model
Deposition, Re-entrainment,Rebound and Breakage
Particle-ParticleInteraction Model
Coalescence, Agglomeration,Rebound and Breakage
Sub-Models
Heat Loss Through theInsulation
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Trajectories coloured bymoisture fraction
Moi
stur
eFr
actio
n
w/w20%
(20µm)50%
(46µm)90%
(110 µm)