The evaporation kinetics of pure water droplets at varying drying rates and the use of evaporation rates to infer the gas phase relative humidity

Numerous analytical models have been applied to describe the evaporation/condensation kinetics of volatile components from aerosol particles for use in many applications.

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Conversion of Alkoxide Solutions to Oxides: Evaporation of Products

MRS Proceedings ◽

10.1557/proc-155-163 ◽

1989 ◽

Vol 155 ◽

Author(s):

R. A. Lipeles ◽

D. J. Coleman

Keyword(s):

High Flow ◽

Drying Rate ◽

Flow Rates ◽

Long Time ◽

Drying Rates ◽

Drying Conditions ◽

Kinetics Of ◽

By Products ◽

Evaporation Kinetics ◽

Kinetics Monitoring

ABSTRACTThe evaporation of organic by-products released during drying of 1-mm thick silicon tetramethoxide gels was analyzed using gas chromatography. The evaporation kinetics of methanol depended on the drying rate achieved by flowing dry air over the gel. For drying at flow rates less than 50 cm 3/min, exponential kinetics were observed initially with a long time constant (about 100- to 400-min). For drying rates greater than 70 cm3/min, diffusional (t−1/2) kinetics were observed initially. Cracking of the gel during drying was used to indicate the degree of stress. At low drying rates, minor cracking was observed near the edges of the gel. At high flow rates, extensive cracking was observed in samples that exhibited early t−1/2 kinetics. Monitoring the kinetics of drying is essential to optimizing the drying conditions to minimize stress and cracking in gels.

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Effect of Relative Humidity on Drying Kinetics of Agricultural Products

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.699.257 ◽

2014 ◽

Vol 699 ◽

pp. 257-262

Author(s):

Sulastri Sabudin ◽

Mohd Zairul Hakimi Remlee ◽

Mohd Faizal Mohideen Batcha

Keyword(s):

Relative Humidity ◽

Air Temperature ◽

Energy Efficient ◽

Human Population ◽

Room Temperature ◽

Food Preservation ◽

Agricultural Products ◽

Drying Behavior ◽

Drying Rates ◽

Kinetics Of

The demand for food has been ever increasing in proportion with the growing human population. This includes agricultural products including fruits. Hence, food preservation for extended usage through drying is gaining importance. This study reports the drying behavior of several agricultural products, namely sweet potato, carrot, ginger, turmeric, passion fruit and its rind. Focus has been given to the effect of relative humidity on drying for these products at room temperature. Experiments were carried out at 27°C by varying relative humidity at 40%, 60% and 80%. It was found that the relative humidity has a strong effect on drying, with lower relative humidity providing higher drying rates. In humid surrounding like Malaysia which has an average humidity more than 70%, controlling humidity of drying air may result in an energy efficient process in comparison to raising the drying air temperature

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The effect of gas-phase polycyclic aromatic hydrocarbons on the formation and properties of biogenic secondary organic aerosol particles

Faraday Discussions ◽

10.1039/c7fd00032d ◽

2017 ◽

Vol 200 ◽

pp. 143-164 ◽

Cited By ~ 15

Author(s):

Alla Zelenyuk ◽

Dan G. Imre ◽

Jacqueline Wilson ◽

David M. Bell ◽

Kaitlyn J. Suski ◽

...

Keyword(s):

Polycyclic Aromatic Hydrocarbons ◽

Gas Phase ◽

Aromatic Hydrocarbons ◽

Particle Number ◽

Secondary Organic Aerosol ◽

Organic Aerosol ◽

Chemical Degradation ◽

Volatile Components ◽

Polycyclic Aromatic ◽

Evaporation Kinetics

When secondary organic aerosol (SOA) particles are formed by ozonolysis in the presence of gas-phase polycyclic aromatic hydrocarbons (PAHs), their formation and properties are significantly different from SOA particles formed without PAHs. For all SOA precursors and all PAHs, discussed in this study, the presence of the gas-phase PAHs during SOA formation significantly affects particle mass loadings, composition, growth, evaporation kinetics, and viscosity. SOA particles formed in the presence of PAHs have, as part of their compositions, trapped unreacted PAHs and products of heterogeneous reactions between PAHs and ozone. Compared to ‘pure’ SOA particles, these particles exhibit slower evaporation kinetics, have higher fractions of non-volatile components, like oligomers, and higher viscosities, assuring their longer atmospheric lifetimes. In turn, the increased viscosity and decreased volatility provide a shield that protects PAHs from chemical degradation and evaporation, allowing for the long-range transport of these toxic pollutants. The magnitude of the effect of PAHs on SOA formation is surprisingly large. The presence of PAHs during SOA formation increases mass loadings by factors of two to five, and particle number concentrations, in some cases, by more than a factor of 100. Increases in SOA mass, particle number concentrations, and lifetime have important implications to many atmospheric processes related to climate, weather, visibility, and human health, all of which relate to the interactions between biogenic SOA and anthropogenic PAHs. The synergistic relationship between SOA and PAHs presented here are clearly complex and call for future research to elucidate further the underlying processes and their exact atmospheric implications.

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Effects of Surface Topography and Colloid Particles on the Evaporation Kinetics of Sessile Droplets on Superhydrophobic Surfaces

Journal of Heat Transfer ◽

10.1115/1.4005715 ◽

2012 ◽

Vol 134 (5) ◽

Cited By ~ 12

Author(s):

Wei Xu ◽

Chang-Hwan Choi

Keyword(s):

Rate Constants ◽

Water Droplet ◽

Evaporation Rate ◽

Pure Water ◽

Hydrophobic Surface ◽

Superhydrophobic Surfaces ◽

Clear Correlation ◽

Planar Surface ◽

Kinetics Of ◽

Evaporation Kinetics

In this paper, the evaporation kinetics of microliter-sized sessile droplets of gold colloids (∼250 nm in particle diameters) was experimentally studied on micropatterned superhydrophobic surfaces, compared with those of pure water on a planar hydrophobic surface. The structural microtopography of superhydrophobic surfaces was designed to have a constant air fraction (∼0.8) but varying array patterns including pillars, lines, and wells. During evaporation in a room condition, the superhydrophobic surfaces exhibited a stronger pinning effect than a planar surface, especially in the initial evaporation stage, with significant variations by the surface topographies. Compared to a pure water droplet, colloids exhibited further promoted pinning effects, mainly in the later stage of evaporation. While the well-known evaporative mass transport law of sessile droplets (i.e., linear law of “V2/3∝t”) was generally applicable to the superhydrophobic surfaces, much smaller evaporation rate constants were measured on the patterned superhydrophobic surfaces than on a planar hydrophobic surface. A colloidal droplet further showed lower evaporation rate constants than a pure water droplet as the concentration of particles in the droplets increased over the evaporation. Such transition was more dramatic on a planar surface than on the micropatterned surfaces. Whereas there was no clear correlation between evaporation mode and the evaporation rate observed on the superhydrophobic surfaces, the prominent decrease of the evaporation rate on the planar hydrophobic surface was accompanied with the onset of a second pinning mode.

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Evaporation Kinetics of Sessile Water Droplets on Micropillared Superhydrophobic Surfaces

Langmuir ◽

10.1021/la400452e ◽

2013 ◽

Vol 29 (20) ◽

pp. 6032-6041 ◽

Cited By ~ 88

Author(s):

Wei Xu ◽

Rajesh Leeladhar ◽

Yong Tae Kang ◽

Chang-Hwan Choi

Keyword(s):

Superhydrophobic Surfaces ◽

Water Droplets ◽

Kinetics Of ◽

Evaporation Kinetics

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Glyoxal's impact on dry ammonium salts: fast and reversible surface aerosol browning

10.5194/acp-2020-203 ◽

2020 ◽

Author(s):

David O. De Haan ◽

Lelia N. Hawkins ◽

Kevin Jansen ◽

Hannah G. Welsh ◽

Raunak Pednekar ◽

...

Keyword(s):

Relative Humidity ◽

Gas Phase ◽

Ammonium Sulfate ◽

Aerosol Particles ◽

Ammonium Salts ◽

Carbon Formation ◽

Cloud Droplets ◽

Brown Carbon ◽

Dicarbonyl Compounds ◽

Dry Conditions

Abstract. Alpha-dicarbonyl compounds are believed to form brown carbon in the atmosphere via reactions with ammonium sulfate (AS) in cloud droplets and aqueous aerosol particles. In this work, brown carbon formation in AS and other aerosol particles was quantified as a function of relative humidity (RH) during exposure to gas-phase glyoxal (GX) in chamber experiments. Under dry conditions (RH

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Measurements of the timescales for the mass transfer of water in glassy aerosol at low relative humidity and ambient temperature

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-4739-2011 ◽

2011 ◽

Vol 11 (10) ◽

pp. 4739-4754 ◽

Cited By ~ 132

Author(s):

H.-J. Tong ◽

J. P. Reid ◽

D. L. Bones ◽

B. P. Luo ◽

U. K. Krieger

Keyword(s):

Mass Transfer ◽

Glass Transition ◽

Relative Humidity ◽

Gas Phase ◽

Mass Transfer Rate ◽

Solution Viscosity ◽

Bulk Solution ◽

Size Change ◽

Return To Equilibrium ◽

Kinetics Of

Abstract. The influence of glassy states and highly viscous solution phases on the timescale of aerosol particle equilibration with water vapour is examined. In particular, the kinetics of mass transfer of water between the condensed and gas phases has been studied for sucrose solution droplets under conditions above and below the glass transition relative humidity (RH). Above the glass transition, sucrose droplets are shown to equilibrate on a timescale comparable to the change in RH. Below the glass transition, the timescale for mass transfer is shown to be extremely slow, with particles remaining in a state of disequilibrium even after timescales of more than 10 000 s. A phenomenological approach for quantifying the time response of particle size is used to illustrate the influence of the glassy aerosol state on the kinetics of mass transfer of water: the time is estimated for the droplet to reach the halfway point from an initial state towards a disequilibrium state at which the rate of size change decreases below 1 nm every 10 000 s. This half-time increases above 1000 s once the particle can be assumed to have formed a glass. The measurements are shown to be consistent with kinetic simulations of the slow diffusion of water within the particle bulk. When increasing the RH from below to above the glass transition, a particle can return to equilibrium with the gas phase on a timescale of 10's to 100's of seconds, once again forming a solution droplet. This is considerably shorter than the timescale for the size change of the particle when glassy and suggests that the dissolution of the glassy core can proceed rapidly, at least at room temperature. Similar behaviour in the slowing of the mass transfer rate below the glass transition RH is observed for binary aqueous raffinose solution droplets. Mixed component droplets of sucrose/sodium chloride/water also show slow equilibration at low RH, illustrating the importance of understanding the role of the bulk solution viscosity on the rate of mass transfer with the gas phase, even under conditions that may not lead to the formation of a glass.

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The effect of phase partitioning of semivolatile compounds on the measured CCN activity of aerosol particles

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-6-8413-2013 ◽

2013 ◽

Vol 6 (5) ◽

pp. 8413-8433 ◽

Cited By ~ 3

Author(s):

S. Romakkaniemi ◽

A. Jaatinen ◽

A. Laaksonen ◽

A. Nenes ◽

T. Raatikainen

Keyword(s):

Ammonium Nitrate ◽

Gas Phase ◽

Aerosol Particles ◽

Test Compound ◽

Ambient Conditions ◽

Compound A ◽

Phase Partitioning ◽

Maximum Water ◽

Kinetics Of ◽

Ccn Activity

Abstract. The effect of inorganic semivolatile aerosol compounds on the CCN activity of aerosol particles was studied by using a computational model for a DMT-CCN counter, a cloud parcel model for condensation kinetics and experiments to quantify the modelled results. Concentrations of water vapour and semivolatiles as well as aerosol trajectories in the CCN column were calculated by a computational fluid dynamics model. These trajectories and vapour concentrations were then used as an input for the cloud parcel model to simulate mass transfer kinetics of water and semivolatiles between aerosol particles and the gas phase. Two different questions were studied: (1) how big fraction of semivolatiles is evaporated from particles before activation in the CCN counter? (2) How much the CCN activity can be increased due to condensation of semivolatiles prior to the maximum water supersaturation in the case of high semivolatile concentration in the gas phase? The results show that, to increase the CCN activity of aerosol particles, a very high gas phase concentration (as compared to typical ambient conditions) is needed. We used nitric acid as a test compound. A concentration of several ppb or higher is needed for measurable effect. In the case of particle evaporation, we used ammonium nitrate as a test compound and found that it partially evaporates before maximum supersaturation is reached in the CCN counter, thus causing an underestimation of CCN activity. The effect of evaporation is clearly visible in all supersaturations, leading to an underestimation of the critical dry diameter by 10 to 15 nanometres in the case of ammonium nitrate particles in different supersaturations. This result was also confirmed by measurements in supersaturations between 0.1 and 0.7%.

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