scholarly journals Evaporation of water: evaporation rate and collective effects

2016 ◽  
Vol 798 ◽  
pp. 774-786 ◽  
Author(s):  
Odile Carrier ◽  
Noushine Shahidzadeh-Bonn ◽  
Rojman Zargar ◽  
Mounir Aytouna ◽  
Mehdi Habibi ◽  
...  
Keyword(s):  
Evaporation Rate ◽  
Scaling Law ◽  
Solid Substrate ◽  
Collective Effects ◽  
Water Evaporation ◽  
Length Scale ◽  
Onset Of Convection ◽  
Cooperative Effects ◽  
Evaporative Flux ◽  
Drop Size Distributions

We study the evaporation rate from single drops as well as collections of drops on a solid substrate, both experimentally and theoretically. For a single isolated drop of water, in general the evaporative flux is limited by diffusion of water through the air, leading to an evaporation rate that is proportional to the linear dimension of the drop. Here, we test the limitations of this scaling law for several small drops and for very large drops. We find that both for simple arrangements of drops, as well as for complex drop size distributions found in sprays, cooperative effects between drops are significant. For large drops, we find that the onset of convection introduces a length scale of approximately 20 mm in radius, below which linear scaling is found. Above this length scale, the evaporation rate is proportional to the surface area.

Experimental and numerical studies of magnetoconvection in a rapidly rotating spherical shell

2007 ◽  
Vol 580 ◽  
pp. 123-143 ◽  
Author(s):  
N. GILLET ◽  
D. BRITO ◽  
D. JAULT ◽  
H. C. NATAF
Keyword(s):  
Magnetic Field ◽  
Spherical Shell ◽  
Scaling Law ◽  
Companion Paper ◽  
Magnetic Study ◽  
Critical Parameters ◽  
Liquid Gallium ◽  
Length Scale ◽  
Onset Of Convection ◽  
Conductive Liquid

Thermal magnetoconvection in a rapidly rotating spherical shell is investigated numerically and experimentally in electrically conductive liquid gallium (Prandtl number P = 0.025), at Rayleigh numbers R up to around 6 times critical and at Ekman numbers E ∼ 10−6. This work follows up the non-magnetic study of convection presented in a companion paper (Gillet et al. 2007). We study here the addition of a z-invariant toroidal magnetic field to the fluid flow. The experimental measurements of fluid velocities by ultrasonic Doppler velocimetry, together with the quasi-geostrophic numerical simulations incorporating a three-dimensional modelling of the magnetic induction processes, demonstrate a stabilizing effect of the magnetic field in the weak-field case, characterized by an Elsasser number Λ < (E/P)1/3. We find that this is explained by the changes of the critical parameters at the onset of convection as Λ increases. As in the non-magnetic study, strong zonal jets of characteristic length scales ℓβ (Rhines length scale) dominates the fluid dynamics. A new characteristic of the magnetoconvective flow is the elongation of the convective cells in the direction of the imposed magnetic field, introducing a new length scale ℓφ. Combining experimental and numerical results, we derive a scaling law $\overline{U} \,{\sim}\, (\widetilde{U}_s \widetilde{U}_{\phi})^{2/3} \,{\sim}\, \widetilde{U}_s{}^{4/3} (\ell_{\phi}/\ell_{\beta})^{2/3}$ where U is the axisymmetric motion amplitude, Ũs and Ũφ are the non-axisymmetric radial and azimuthal motion amplitudes, respectively.

scholarly journals Highly efficient evaporative cooling by all-day water evaporation using hierarchically porous biomass

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jihun Choi ◽  
Hansol Lee ◽  
Bokyeong Sohn ◽  
Minjae Song ◽  
Sangmin Jeon
Keyword(s):  
Porous Structure ◽  
Fiber Length ◽  
Evaporation Rate ◽  
Water Evaporation ◽  
Thickness Direction ◽  
Hierarchically Porous ◽  
Hierarchically Porous Structure ◽  
Length Direction ◽  
Luffa Sponge ◽  
Fiber Thickness

AbstractWe developed a 3D solar steam generator with the highest evaporation rate reported so far using a carbonized luffa sponge (CLS). The luffa sponge consisted of entangled fibers with a hierarchically porous structure; macropores between fibers, micro-sized pores in the fiber-thickness direction, and microchannels in the fiber-length direction. This structure remained after carbonization and played an important role in water transport. When the CLS was placed in the water, the microchannels in the fiber-length direction transported water to the top surface of the CLS by capillary action, and the micro-sized pores in the fiber-thickness direction delivered water to the entire fiber surface. The water evaporation rate under 1-sun illumination was 3.7 kg/m2/h, which increased to 14.5 kg/m2/h under 2 m/s wind that corresponded to the highest evaporation rate ever reported under the same condition. The high evaporation performance of the CLS was attributed to its hierarchically porous structure. In addition, it was found that the air temperature dropped by 3.6 °C when the wind passed through the CLS because of the absorption of the latent heat of vaporization. The heat absorbed by the CLS during water evaporation was calculated to be 9.7 kW/m2 under 1-sun illumination and 2 m/s wind, which was 10 times higher than the solar energy irradiated on the same area (1 kW/m2).

scholarly journals Experimental Measurements of the Water Evaporation Rate of a Physical Model

2017 ◽  
Vol 25 (1) ◽  
pp. 19-23 ◽  
Author(s):  
Róbert Turza ◽  
Belo B. Füri
Keyword(s):  
Energy Demand ◽  
Evaporation Rate ◽  
High Water ◽  
Hvac Systems ◽  
Swimming Pool ◽  
Water Evaporation ◽  
Specific Enthalpy ◽  
High Water Content ◽  
Indoor Environments ◽  
Indoor Swimming Pool

Abstract As the number of indoor swimming pools and wellness centers are currently growing, it is necessary to concentrate on the parameters of indoor environments. These parameters are necessary for the design of the HVAC systems that operate these premises. In indoor swimming-pool facilities, the energy demand is large due to ventilation losses from exhaust air. Since water evaporates from a pool’s surface, exhaust air has a high water content and specific enthalpy. In this paper the results of the water evaporation rate measured from swimming pool surfaces at higher thermal water temperatures are described.

scholarly journals Scaling and Similarity of the Anisotropic Coherent Eddies in Near-Surface Atmospheric Turbulence

2018 ◽  
Vol 75 (3) ◽  
pp. 943-964 ◽  
Author(s):  
Khaled Ghannam ◽  
Gabriel G. Katul ◽  
Elie Bou-Zeid ◽  
Tobias Gerken ◽  
Marcelo Chamecki
Keyword(s):  
Scaling Laws ◽  
Velocity Structure ◽  
Scaling Law ◽  
Longitudinal Velocity ◽  
Structure Functions ◽  
Length Scale ◽  
Near Surface ◽  
Vegetation Canopies ◽  
Velocity Spectra ◽  
Attached Eddies

Abstract The low-wavenumber regime of the spectrum of turbulence commensurate with Townsend’s “attached” eddies is investigated here for the near-neutral atmospheric surface layer (ASL) and the roughness sublayer (RSL) above vegetation canopies. The central thesis corroborates the significance of the imbalance between local production and dissipation of turbulence kinetic energy (TKE) and canopy shear in challenging the classical distance-from-the-wall scaling of canonical turbulent boundary layers. Using five experimental datasets (two vegetation canopy RSL flows, two ASL flows, and one open-channel experiment), this paper explores (i) the existence of a low-wavenumber k−1 scaling law in the (wind) velocity spectra or, equivalently, a logarithmic scaling ln(r) in the velocity structure functions; (ii) phenomenological aspects of these anisotropic scales as a departure from homogeneous and isotropic scales; and (iii) the collapse of experimental data when plotted with different similarity coordinates. The results show that the extent of the k−1 and/or ln(r) scaling for the longitudinal velocity is shorter in the RSL above canopies than in the ASL because of smaller scale separation in the former. Conversely, these scaling laws are absent in the vertical velocity spectra except at large distances from the wall. The analysis reveals that the statistics of the velocity differences Δu and Δw approach a Gaussian-like behavior at large scales and that these eddies are responsible for momentum/energy production corroborated by large positive (negative) excursions in Δu accompanied by negative (positive) ones in Δw. A length scale based on TKE dissipation collapses the velocity structure functions at different heights better than the inertial length scale.

scholarly journals Calculation of Water Evaporative Cooling Systems in Animal Husbandry

2020 ◽  
pp. 35-38
Author(s):  
N.N. Novikov ◽  
Keyword(s):  
Air Conditioning ◽  
Evaporation Rate ◽  
Evaporative Cooling ◽  
Animal Husbandry ◽  
Water Evaporation ◽  
Cooling Systems ◽  
Temperature And Humidity ◽  
Hot Weather ◽  
Livestock Building ◽  
Air Exchange

A method for calculating the parameters of the microclimate in a livestock building using water-evaporative air conditioning is described. It makes it possible to choose a rational temperature and humidity conditions for a room in hot weather, calculate the required air exchange, water evaporation rate and select the appropriate equipment.

scholarly journals Influence of Magnetic Field on Evaporation Rate and Surface Tension of Water

2018 ◽  
Vol 2 (4) ◽  
pp. 68 ◽  
Author(s):  
Emil Chibowski ◽  
Aleksandra Szcześ ◽  
Lucyna Hołysz
Keyword(s):  
Magnetic Field ◽  
Surface Tension ◽  
Hydrogen Bonds ◽  
Room Temperature ◽  
Evaporation Rate ◽  
Water Evaporation ◽  
Water Molecules ◽  
Surface Tension Data ◽  
Ring Magnet ◽  
The Magnetic Field

Using neodymium ring magnets (0.5–0.65 T), the experiments on the magnetic field (MF) effects on water evaporation rate and surface tension were performed at room temperature (22–24 °C). In accordance with the literature data, the enhanced evaporation rates were observed in the experiments conducted in a period of several days or weeks. However, the evaporated amounts of water (up to 440 mg over 150 min) in particular experiments differed. The evaporated amounts depended partially on which pole of the ring magnet was directed up. The relatively strong MF (0.65 T) caused a slight decrease in surface tension (−2.11 mN/m) which lasted longer than 60 min and the memory effect vanished slowly. The surface tension data reduced by the MF action are reported in the literature, although contrary results can be also found. The observed effects can be explained based on literature data of molecular simulations and the suggestion that MF affects the hydrogen bonds of intra- and inter-clusters of water molecules, possibly even causing breakage some of them. The Lorentz force influence is also considered. These mechanisms are discussed in the paper.

Three-dimensional water evaporation on a macroporous vertically aligned graphene pillar array under one sun

2018 ◽  
Vol 6 (31) ◽  
pp. 15303-15309 ◽  
Author(s):  
Panpan Zhang ◽  
Qihua Liao ◽  
Houze Yao ◽  
Huhu Cheng ◽  
Yaxin Huang ◽  
...  
Keyword(s):  
Evaporation Rate ◽  
Three Dimensional ◽  
Water System ◽  
Water Evaporation ◽  
Solar Water Heater ◽  
Water Heater ◽  
Wastewater Purification ◽  
Pillar Array ◽  
System P ◽  
Vertically Aligned

Three-dimensional water evaporation is proposed based on highly vertically ordered pillar array of graphene-assembled framework (HOPGF). A high evaporation rate of 2.10 kg m−2 h−1 is achieved (1 sun). This efficient SSG system has been applied to wastewater purification, solar water heater and housing self-supply water system.

A Research on Eliminating the Deposited Water After Water-Ingress Accident in HTR

2013 ◽  
Author(s):  
Peng Liu ◽  
Yanhua Zheng
Keyword(s):  
Steam Generator ◽  
Empirical Formula ◽  
Nuclear Power ◽  
Evaporation Rate ◽  
Computing Methods ◽  
Temperature Fields ◽  
Water Evaporation ◽  
Ansys Fluent ◽  
Forced Circulation ◽  
Water Ingress

Water-ingress accident, caused by steam generator heating tube rupture of a high temperature gas-cooled reactor (HTGR) is an important accident to consider because it will introduce positive reactivity leading the nuclear power increase rapidly, as well as the chemical reaction of graphite fuel elements and reflector structure material with steam. Researches and simulations (Zuoyi Zhang et al. 1995; Zheng Yanhua et al. 2009) have been carried out for calculating the total amount of water ingress and to validate the safety and security of HTR. The water ingress amount, which is our mainly concerned, ranges from a few hundred kilograms to thousands of kilograms, because of the different reactors and different computing methods. The place, where the water deposits, is most likely to be the bottom of the steam generator.. Such liquid water removal, with the approach of providing a forced circulation in primary loop and accelerating the evaporation, is analyzed in this paper. Many experimental data have been got on water evaporation rate (Dalton et al.; Willis Carrie et al. 1914; Yoshida, Hyodo et al. 1970; Sweer et al. 1976; Pauken et al. 1995). All these formulas have a common form, ṁ = hc(Pw − Pa)/hw, which shows the relationship between evaporation rate and velocity over water face, water temperature and the relative partial pressure of the water vapor. This formula has been used widely in chemical industry and other fields and shows good agreement. FLUENT CFD code (ANSYS Fluent 14) is used for the calculation of the distribution of the flow and temperature fields. The evaporation rate is estimate combined thermal fluid data with empirical formula. As the working condition of empirical formula and that of actual reactor don’t match very well, sensitivity analysis is necessary in this report.

scholarly journals Effect of air parameters, water temperature, and number of pool occupants on moisture gains

2018 ◽  
Vol 70 ◽  
pp. 02006
Author(s):  
Agnieszka Garnysz-Rachtan ◽  
Zbigniew Zapałowicz
Keyword(s):  
Water Temperature ◽  
Water Surface ◽  
Evaporation Rate ◽  
Water Evaporation ◽  
Physical Parameters ◽  
Air Humidity ◽  
Air Velocity ◽  
Relative Air Humidity ◽  
Thermal Calculations ◽  
The Right

Thermal calculations for indoor swimming pools require that amount of water evaporated from the pool's water surface, as well as water evaporated from the floor surrounding the pool and from the bodies of the occupants are to be determined. It means in practice that amount of vapor transferred to the air in the pool hall depends most of all on physical parameters of water and air. One of more important factors that affect water evaporation is also the way the pool is operated. The present article shows only chosen relations applied to determine the values of evaporation rate from occupied pool. The relations also account for the mode of pool's operation. The aim of the paper is to analyse the effect of changes of temperature and of relative air humidity in the hall, of water temperature and of air velocity above the water surface, as well as of the number of occupants on moisture gains in the hall. The above data let choose the right relation to be applied in calculations for the water evaporation rate.

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