Effects of the Relative Humidity and Water Droplet on Adhesion of a Bio-inspired Nanofilm

2015 ◽  
pp. 71-81
Author(s):  
Zhilong Peng
Keyword(s):  
Relative Humidity ◽  
Water Droplet

On the Influence of Relative Humidity on the Contact Angle of a Water Droplet on a Silicon Wafer

2013 ◽  
Author(s):  
J. L. Perez-Diaz ◽  
M. A. Alvarez-Valenzuela ◽  
I. Valiente-Blanco ◽  
S. Jimenez-Lopez ◽  
M. Palacios-Cuesta ◽  
...  
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Relative Humidity ◽  
Silicon Wafer ◽  
Water Droplet ◽  
Measurement Techniques ◽  
Contact Angle Measurement ◽  
Angle Measurement ◽  
Wafer Surface ◽  
Free Energy Surface

Contact angle analysis of liquids on surfaces has been extensively used to evaluating solid surface free energy, surface tension, and surface wetting characteristics. Despite the great interest in the contact angle, reported measurements has shown a high variety, which is often related to different contact angle measurement techniques or substrate preparation and oxidation among others. In addition, it is well know, that surface tension and contact angle are modified with temperature. However, no attention has been paid to the influence of the relative humidity (RH) in surface tension or contact angle measurements. In a previous work, we have demonstrated that (for a constant temperature) surface tension on a suspended droplet decreases linearly with RH in the air. In this paper, contact angle of a water droplet on a silicon wafer surface is studied and its relationship with the relative humidity in the air investigated.

scholarly journals Modelling investigation of water droplet evaporative freezing in artificial snowmaking

2019 ◽  
Vol 128 ◽  
pp. 06013
Author(s):  
Georges El Achkar ◽  
Aiqiang Chen ◽  
Rachid Bennacer ◽  
Bin Liu
Keyword(s):  
Heat Transfer ◽  
Numerical Model ◽  
Relative Humidity ◽  
Air Temperature ◽  
Water Droplet ◽  
Theoretical Models ◽  
Comsol Multiphysics ◽  
Initial Diameter ◽  
Air Space ◽  
Mass And Heat Transfer

In this paper, a modelling investigation of water droplet evaporative freezing was conducted in order to better understand the snowmaking process and hence to optimise the design of the artificial snowmaking device. To this end, mass and heat transfer theoretical models of a single water droplet cooling in an air space were established and implemented in a numerical model developed using the software COMSOL Multiphysics. The effects of the air temperature, relative humidity and velocity and the water droplet initial diameter and temperature on this process were identified and analysed, and their appropriate ranges for the snowmaking were determined.

scholarly journals Effect of relative humidity on heat transfer across the surface of an evaporating water droplet in air flow

2009 ◽  
Vol 624 ◽  
pp. 57-67 ◽  
Author(s):  
RYOICHI KUROSE ◽  
AKITOSHI FUJITA ◽  
SATORU KOMORI
Keyword(s):  
Heat Transfer ◽  
Relative Humidity ◽  
Heat Loss ◽  
Water Droplet ◽  
Rear Surface ◽  
Ambient Air ◽  
Droplet Surface ◽  
Droplet Temperature ◽  
Humidity Condition ◽  
Evaporation Heat

A three-dimensional direct numerical simulation (DNS) is applied to flows inside and outside an evaporating spherical water droplet in air, and the effect of relative humidity on the heat transfer between the droplet and ambient air is investigated. The initial air temperature is set to be 15 K higher than the initial droplet temperature. The results show that the local evaporation heat loss indicates the maximum on the front of the droplet and decreases on going from the front to the rear, and the reduction on the rear becomes marked for high-droplet Reynolds numbers. This is because the evaporation rate is suppressed on the rear surface by the presence of flow separations behind the droplet. The droplet temperature decreases in the low-humidity condition, whereas it increases in the high-humidity condition. This difference is caused by the heat balance of evaporation heat loss and convective heat gain from ambient air at the droplet surface.

scholarly journals Freezing of water droplets colliding with kaolinite particles

2009 ◽  
Vol 9 (13) ◽  
pp. 4295-4300 ◽  
Author(s):  
E. A. Svensson ◽  
C. Delval ◽  
P. von Hessberg ◽  
M. S. Johnson ◽  
J. B. C. Pettersson
Keyword(s):  
Water Vapor ◽  
Relative Humidity ◽  
Water Droplet ◽  
Supercooled Water ◽  
Dust Particles ◽  
Freezing Process ◽  
Water Droplets ◽  
Electrodynamic Balance ◽  
Dry Conditions

Abstract. Contact freezing of single supercooled water droplets colliding with kaolinite dust particles has been investigated. The experiments were performed with droplets levitated in an electrodynamic balance at temperatures from 240 to 268 K. Under relatively dry conditions (when no water vapor was added) freezing was observed to occur below 249 K, while a freezing threshold of 267 K was observed when water vapor was added to the air in the chamber. The effect of relative humidity is attributed to an influence on the contact freezing process for the kaolinite-water droplet system, and it is not related to the lifetime of the droplets in the electrodynamic balance. Freezing probabilities per collision were derived assuming that collisions at the lowest temperature employed had a probability of unity. Mechanisms for contact freezing are briefly discussed.

Effects of Ambient Air Relative Humidity and Surface Temperature on Water Droplet Spreading Dynamics

2018 ◽  
Author(s):  
M. Jadidi ◽  
M. A. Farzad ◽  
J. Y. Trepanier ◽  
A. Dolatabadi
Keyword(s):  
Contact Angle ◽  
Relative Humidity ◽  
Surface Temperature ◽  
Air Temperature ◽  
Water Droplet ◽  
Superhydrophobic Surface ◽  
High Speed ◽  
Ambient Air ◽  
Dew Point ◽  
Droplet Spreading

Water droplet impact on horizontal glass, aluminum, and superhydrophobic surfaces is experimentally investigated using high speed imaging. Experiments are performed at three different relative humidities (i.e. 10, 20 and 30%) and three surface temperatures (i.e. 20, 2 and −2°C) to ascertain their effects on droplet spreading and recoil behaviors. In this study, the droplet Weber number, Reynolds number, and the ambient air temperature are fixed at 16.2, 1687, and 23°C, respectively. The high-speed images of impact, spreading and recoil of the droplets as well as the temporal variations of droplet spreads are prepared. Results show that the ratio of surface temperature to dew point temperature (which depends on the air temperature and relative humidity) has a significant influence on droplet spreading, recoil, and contact angle. When this ratio is less than one, condensation and frost formation become important. Decreasing the mentioned ratio (it can be done by decreasing the surface temperature or increasing the relative humidity) causes the droplet spreading factor for hydrophilic surfaces to increase significantly. For superhydrophobic surface, decreasing this ratio (within the mentioned range) does not influence the maximum spreading. However, the recoiling phase is slowed down and the droplet detachment time form the superhydrophobic surface is increased noticeably. In addition, the equilibrium contact angle decreases as the mentioned ratio decreases.

EPIDEMIOLOGY, ECOLOGY AND PREVALENCE OF SOIL TRANSMITTED HELMINTHS FROM KOSHI REGION OF NORTH BIHAR.

2018 ◽  
Vol 24 (1) ◽  
Author(s):  
LAKSHMI CHOUDHARY ◽  
PRABHAWATI PRABHAWATI
Keyword(s):  
Relative Humidity ◽  
Ascaris Lumbricoides ◽  
Rainy Season ◽  
Climatic Factors ◽  
Trichuris Trichiura ◽  
Hookworm Infection ◽  
Soil Transmitted Helminths ◽  
High Incidence ◽  
Apparently Healthy

Prevalence of soil transmitted helminthes infections in apparently healthy school going children and other 528 people of different districts of Koshi regions of North Bihar were evaluated. Over all incidences of STHs infection was 39.39% during study. High incidence of STH was seen in the rainy season i.e., in the month of July and August, September, significantly higher (P<0.05) .The incidence of Ascaris lumbricoides was highest in the month of August (18.64%). The month of September was 15.25% followed by that of July (14.4%) and October with 10.16%. Also the incidence of hookworm registered the highest incidence in the month of June (19.27%) and lowest in the month of December (4.82%) during the study period. However prevalence of Trichuris trichiura was negligible and it was almost nil in the most of the months but was highest in month of September with 28.57% and lowest in October with 14.00% The climatic factors are responsible for soil transmitted helminthes which are temperature, rainfall and relative humidity. Ascariasis, Trichuriasis and Ancyclostomiasis (Hookworm infection) are found to be endemic in this region.

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