Evaporation and movement of fine droplets in non-uniform temperature and humidity field

Wang, Yi; Wu, Songheng; Yang, Yang; Yang, Xiaoni; Song, Han; Cao, Zhixiang; Huang, Yanqiu

doi:10.1016/j.buildenv.2019.01.003

Cited by 21 publications

(15 citation statements)

References 43 publications

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“…Wang et al [ 51 ] conducted a series of studies on the effects of ambient temperature, humidity, and initial particle size on evaporation, and their results showed that the impact of these three factors on the evaporation characteristics of droplet was not independent; therefore the influence of any factor on droplet evaporation cannot be discussed without the other factors. Additionally, Li et al and Yan et al [ 22 , 52 ] established an evaporation model of cough droplets under non-uniform humidity conditions, simulating the propagation distance and distribution characteristics of different size droplets.…”

Section: Resultsmentioning

confidence: 99%

Transmission risk of infectious droplets in physical spreading process at different times: A review

Mao

Guo

et al. 2020

Building and Environment

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Droplets provide a well-known transmission media in the COVID-19 epidemic, and the particle size is closely related to the classification of the transmission route. However, the term “aerosol” covers most particle sizes of suspended particulates because of information asymmetry in different disciplines, which may lead to misunderstandings in the selection of epidemic prevention and control strategies for the public. In this review, the time when these droplets are exhaled by a patient was taken as the initial time. Then, all available viral loads and numerical distribution of the exhaled droplets was analyzed, and the evaporation model of droplets in the air was combined with the deposition model of droplet nuclei in the respiratory tract. Lastly, the perspective that physical spread affects the transmission risk of different size droplets at different times was summarized for the first time. The results showed that although the distribution of exhaled droplets was dominated by small droplets, droplet volume was proportional to the third power of particle diameter, meaning that the viral load of a 100 μm droplet was approximately 10 6 times that of a 1 μm droplet at the initial time. Furthermore, the exhaled droplets are affected by heat and mass transfer of evaporation, water fraction, salt concentration, and acid-base balance (the water fraction > 98%), which lead them to change rapidly, and the viral survival condition also deteriorates dramatically. The time required for the initial diameter (d o ) of a droplet to shrink to the equilibrium diameter (d e , about 30% of d o ) is approximately proportional to the second power of the particle diameter, taking only a few milliseconds for a 1 μm droplet but hundreds of milliseconds for a 10 μm droplet; in other words, the viruses carried by the large droplets can be preserved as much as possible. Finally, the infectious droplet nuclei maybe inhaled by the susceptible population through different and random contact routes, and the droplet nuclei with larger d e decompose more easily into tiny particles on account of the accelerated collision in a complex airway, which can be deposited in the higher risk alveolar region. During disease transmission, the infectious droplet particle size varies widely, and the transmission risk varies significantly at different time nodes; therefore, the fuzzy term “aerosol” is not conducive to analyzing disease exposure risk. Recommendations for epidemic prevention and control strategies are: 1) Large droplets are the main conflict in disease transmission; thus, even if they are blocked by a homemade mask initially, it significantly contains the epidemic. 2) The early phase of contact, such as close-contact and short-range transmission, has the highest infection risk; therefore, social distancing can effectively keep the susceptible population from inhaling active viruses. 3) The risk of the fomite route depends on ...

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Section: Resultsmentioning

confidence: 99%

Transmission risk of infectious droplets in physical spreading process at different times: A review

Mao

Guo

et al. 2020

Building and Environment

View full text Add to dashboard Cite

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“…The RH is maintained at a high level (75%) during the contact angle measurement to reduce the effect of evaporation. 52 During the tests, the shapes of the water droplets on the shale samples were recorded using a high-speed camera ( Figure 9 ). It can be seen from Figure 9 that the contact line between the shale sample and water droplet did not change significantly from 1 to 7 min.…”

Section: Samples and Experimentsmentioning

confidence: 99%

Experimental Study of the Wettability Characteristic of Thermally Treated Shale

Yang

Gu²,

Chen

et al. 2020

ACS Omega

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Extraction of shale gas from shale reservoirs is significantly affected by shale wettability. Recently, thermal recovery technologies (e.g., combustion) have been tested for shale gas recovery. This requires an understanding of the wettability change mechanism for thermally treated shale samples. In this study, the effect of combustion on shale wettability was investigated. Shale samples were first processed to obtain smooth surfaces and then combusted at temperatures of 200, 400, and 800 °C. The initial contact angles and dynamic behavior of water droplets on shale surfaces were recorded using the sessile drop method. It was found that pores and fractures were generated on the shale surfaces following high-temperature combustion. The pore volume and diameter increased with increasing combustion temperature, which improved the connectivity of hydrophilic pore networks. Compared to a raw shale sample, the shale sample combusted at 400 °C showed a smaller initial water contact angle and a more rapid decrease in the contact angle because of the oxidation of organic matter and generation of pore structures. Water droplets were found to completely spread over the surface of the shale sample combusted at 800 °C because of the generation of fractures. Moreover, the van der Waals potential between water droplets and combusted shale samples was determined to be stronger. However, the initial contact angle and dynamic behavior of water droplets did not show a significant change for the shale sample combusted at 200 °C. As a result, high-temperature combustion (≥400 °C) can be used to significantly improve the hydrophilicity of shale.

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“…For the indoor environment, such droplet/particle-vapor interaction has attracted attention when researchers attempted to model the droplets/particles transport dynamics generated from different sources. For example, Wang et al (2019) recently simulated the evaporation of large droplets (20–80 μm) in a simplified 2D industrial building with different ambient temperature and RH conditions. Water droplets were employed to represent the industrial airborne pollutants in the form of droplets.…”

Section: Introductionmentioning

confidence: 99%

Modeling of the transport, hygroscopic growth, and deposition of multi-component droplets in a simplified airway with realistic thermal boundary conditions

Chen

Zhou

Xia

et al. 2021

Journal of Aerosol Science

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Accurate predictions of the droplet transport, evolution, and deposition in human airways are critical for the quantitative analysis of the health risks due to the exposure to the airborne pollutant or virus transmission. The droplet/particle-vapor interaction, i.e., the evaporation or condensation of the multi-component droplet/particle, is one of the key mechanisms that need to be precisely modeled. Using a validated computational model, the transport, evaporation, hygroscopic growth, and deposition of multi-component droplets were simulated in a simplified airway geometry. A mucus-tissue layer is explicitly modeled in the airway geometry to describe mucus evaporation and heat transfer. Pulmonary flow and aerosol dynamics patterns associated with different inhalation flow rates are visualized and compared. Investigated variables include temperature distributions, relative humidity (RH) distributions, deposition efficiencies, droplet/particle distributions, and droplet growth ratio distributions. Numerical results indicate that the droplet/particle-vapor interaction and the heat and mass transfer of the mucus-tissue layer must be considered in the computational lung aerosol dynamics study, since they can significantly influence the precise predictions of the aerosol transport and deposition. Furthermore, the modeling framework in this study is ready to be expanded to predict transport dynamics of cough/sneeze droplets starting from their generation and transmission in the indoor environment to the deposition in the human respiratory system.

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Evaporation and movement of fine droplets in non-uniform temperature and humidity field

Cited by 21 publications

References 43 publications

Transmission risk of infectious droplets in physical spreading process at different times: A review

Transmission risk of infectious droplets in physical spreading process at different times: A review

Experimental Study of the Wettability Characteristic of Thermally Treated Shale

Modeling of the transport, hygroscopic growth, and deposition of multi-component droplets in a simplified airway with realistic thermal boundary conditions

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