Measured Evaporation Rates Research Articles

Do Lipids Retard the Evaporation of the Tear Fluid?

We examined in vitro the potential evaporation-retarding effect of the tear film lipid layer (TFLL). The artificial TFLL compositions used here were based on the present knowledge of TFLL composition. A custom-built system was developed to measure evaporation rates at 35°C. Lipids were applied to an air-water interface, and the evaporation rate through the lipid layer was defined as water loss from the interface. A thick layer of olive oil and a monolayer of long-chain alcohol were used as controls. The artificial TFLLs were composed of 1 to 4 lipid species: polar phosphatidylcholine (PC), nonpolar cholesteryl ester, triglycerides, and wax ester (WE). Brewster angle microscopy (BAM) and interfacial shear rheometry (ISR) were used to assess the lateral structure and shear stress response of the lipid layers, respectively. Olive oil and long-chain alcohol decreased evaporation by 54% and 45%, respectively. The PC monolayer and the four-component mixtures did not retard evaporation. WE was the most important evaporation-retardant TFLL lipid (∼20% decrease). In PC/WE mixtures, an ∼90% proportion of WE was required for evaporation retardation. Based on BAM and ISR, WE resulted in more condensed layers than the non-retardant layers. Highly condensed, solid-like lipid layers, such as those containing high proportions of WEs, are evaporation-retardant. In multi-component lipid layers, the evaporation-retardant interactions between carbon chains decrease and, therefore, these lipid layers do not retard evaporation.

Resonant MEMS Mass Sensors for Measurement of Microdroplet Evaporation

Microelectromechanical systems (MEMS)-based resonant mass sensors have been extensively studied due to their high sensitivity and small size, making them very suitable for detecting micro- or nanosized particles, as well as monitoring microscaled physical processes. In a range of physical and biological applications, accurate estimation and precise control of the evaporation process of microdroplets are very important. However, due to the lack of appropriate measurement tools, the evaporation process of microdroplets has not been well characterized. Here, we introduce a self-oscillating MEMS mass sensor with a uniform mass sensitivity to directly measure the mass changes of evaporating microdroplets. The mass sensor has a unique spring structure to provide spatially uniform mass sensitivity. The sensor's velocity is fed back to the actuation signal to induce self-oscillation, enabling rapid determination of the resonant frequency. The evaporation rates of single microdroplets of dimethyl sulfoxide and water at various temperatures are obtained. With the measured evaporation rates and the simulated surface area of the microdroplet, the enthalpies of vaporization of both liquids are extracted and found to be in agreement with those in the literature. The method developed in this work can be a valuable tool to enhance our understanding of microscaled physical processes involving rapid mass change, such as evaporation, deposition, self-assembly, cryopreservation, and other biological applications.

Gas phase synthesis of Ni3Fe nanoparticles by magnesium reduction of metal chlorides

FeCl2(g) and NiCl2(g) were used for chemical vapor synthesis of Ni3Fe nanosized intermetallic particles with Mg(g) as the reducing agent. The simultaneous reduction of the chlorides was performed in a tubular furnace with argon as the carrier gas under different gas flow rates and temperatures. Thermodynamic analysis based on the measured evaporation rate of the reactants predicted the formation of Ni3Fe compound. FESEM micrographs, X‐ray diffraction and WDS analysis of the resulting compound identified formation of homogeneous spherical nanosized Ni3Fe compound with a relatively narrow particle size distribution and geometrical mean diameter ranging from 134 to 66nm. Results showed that increasing the argon flow rate from 0.6 to 1.4l/min significantly decreased the average particle size at all temperatures because of a reduction in residence time and reactant concentration. Increasing the synthesis temperature from 895 to 1020°C reduced the average particle size probably because of higher nucleation rate.

Natural Dewatering of Marine Dredged Sediments

The aim of this study is to explore the water content decrease in dredged sediment by natural evaporation and/or drainage. This operation constitutes, in several fields, a preliminary operation to insure a reliable beneficial use of this material. Firstly, a methodology is proposed to assess the relative efficiency of drainage and evaporation in the process of water content reduction in the dredged sediment. Secondly, comparisons of measured evaporation rates are compared to predictions of an available model in the literature. Thirdly, the observed stages during drying are explained in the light of standard parameters measured on the sediment. Finally, a relationship between water content decrease and increase of shear strength of the sediment is discussed. These results will allow a better management of beneficial use of the sediment and enhance scheduling of the drying operation and its transport.

The vapor pressures and activities of dicarboxylic acids reconsidered: the impact of the physical state of the aerosol

Abstract. We present vapor pressure data of the C2 to C5 dicarboxylic acids deduced from measured evaporation rates of single levitated particles as both, aqueous droplets and solid crystals. The data of aqueous solution particles over a wide concentration range allow us to directly calculate activities of the dicarboxylic acids and comparison of these activities with parameterizations reported in the literature. The data of the pure liquid state acids, i.e. the dicarboxylic acids in their supercooled melt state, exhibit no even-odd alternation in vapor pressure, while the acids in the solid form do. This observation is consistent with the known solubilities of the acids and our measured vapor pressures of the supercooled melt. Thus, the gas/particle partitioning of the different dicarboxylic acids in the atmosphere depends strongly on the physical state of the aerosol phase, the difference being largest for the even acids. Our results show also that, in general, measurements of vapor pressures of solid dicarboxylic acids may be compromised by the presence of polymorphic forms, crystalline structures with a high defect number, and/or solvent inclusions in the solid material, yielding a higher vapor pressure than the one of the thermodynamically stable crystalline form at the same temperature.

A model for soil surface evaporation based on Campbell’s retention curve

The objective of this study was to develop and verify a simple analytical model for one-dimensional non-steady upward flow from shallow and falling water table with minimum input data. Consequently, an analytical model was derived based on the Richards’ equation with the Campbell’s parametric retention model. This study proposes a model that uses the measurement of water table depth drawdown and some soil physical properties to estimate evaporation, instead of measuring evaporation rate itself. Nine relatively large lysimeters were packed with sandy loam, silty clay loam, and silty clay soil textures to obtain the data needed for evaluating the proposed model. The results indicate a reasonable agreement between the experimental data and the proposed model (root mean square error, RMSE = 2.11–4.22 mm/day). For the experimental period (64 days), however, there is some discrepancy between observation and simulation data. The reasons for this discrepancy may be attributed to vapor upward flow, evaporation which takes place from the lysimeters side gaps resulting from soil shrinkage and collapse of macropores resulting from soil packing.

Measuring the Drying Rate of Liquid Film Coatings Using Heat Flux Method

We propose a simple method of determining solvent drying rates from heat flux measurements across thin liquid films. The theory is based on quasi-steady conductive heat transport through coatings, combined with simultaneous heat and mass transfer in the gas phase. The measured evaporation rates well reproduce conventional gravimetric measurements with an uncertainty of less than 5%. Drying experiments also revealed that the proposed method is robust in systems with high levels of fluctuation and thus provides an alternative tool for monitoring drying kinetics in forced air flows.

Impact of ambient temperature on evaporation from surface‐exposed fractures

Surface‐exposed fractures (SEFs) form a unique link between the atmosphere and the deep vadose zone. Quantifying evaporation and salt‐accumulation rates within these SEFs is essential for understanding processes leading to groundwater salinization and contamination via these fractures. In this study, evaporation from SEFs (ESEFs) was quantified, mainly as a function of ambient atmospheric temperature, by using large‐scale laboratory experiments and measuring evaporation under controlled conditions. In addition, ESEF was theoretically quantified based on the physical processes that govern it. The theoretical model was used to analyze ESEF rates as a function of ambient temperature, temperature gradient, fracture‐aperture, and matrix pore size. ESEF was experimentally found to increase as the ambient temperature decreased. Measured evaporation rates were between about 110 and 260 g d−1 per square meter of fracture surface, for temperature differences between rock‐bottom and the atmosphere of 0° and 13°C, respectively. Comparing these values with model results suggests that convection is the driving process for enhanced evaporation at low ambient temperatures. Finally, we show that ESEF rates decrease as a result of salt precipitation. During a ∼9‐month period, with an imposed temperature difference of 13°C, ESEF decreased from ∼260 to ∼95 g d−1 m−2 due to salt accumulation near and on the fracture surfaces. Evaporation rates began decreasing after about 100 g m−2 of salt had precipitated and decreased to less than 50% of the initial rate after 160 g m−2 of salt had precipitated. We thus show that not only temperature, but also salt precipitation, largely affect ESEF rates.

Thermodynamic Properties of Malonic, Succinic, and Glutaric Acids: Evaporation Rates and Saturation Vapor Pressures

This work provides thermodynamic data, in particular, liquid-state saturation vapor pressures of three common slightly water soluble secondary organic aerosol components, namely, malonic, succinic, and glutaric acids. A modified tandem differential mobility analyzer system was used to measure evaporation rates of nanometer sized aqueous malonic, succinic, and glutaric acid droplets at relative humidities and temperatures relevant in the lower troposphere. Liquid phase saturation vapor pressures and other thermodynamic properties were derived from the measurements using a binary condensation model. The obtained expressions for liquid phase saturation vapor pressures compare well with extrapolated literature data. The importance of the choice of method for calculating activity coefficients is discussed.

Measuring Evaporation Rates of Metal Compounds from Solid Samples

A thermogravimeter (TGA, Mettler-Toledo TGA/SDTA851e) was connected to an inductively coupled plasma optical emission spectrometer (ICP-OES, Varian Liberty 110) using a condensation interface (CI), which transforms gaseous high-boiling-temperature substances into solid (or liquid) aerosols. Argon was used as the carrier gas to transfer the aerosols into the ICP-OES for on-line elemental analysis. This new analytical TGA-CI-ICP-OES device, called TGA-ICP, is the first of its kind and allows one to study the thermochemically induced evaporation behavior of high-boiling-temperature substances, such as heavy metal compounds, under different thermochemical conditions. It allows the investigation of the behavior of large solid or liquid samples (100-500 mg), which is important for applying the results to industrial processes. So far, the CI principle has allowed only semiquantitative elemental analyses of hot gases when connected to an ICP-OES. In this work, we show that a direct calibration of the CI-ICP-OES device is possible in combination with a TGA. The intensities determined by ICP-OES could be directly related to gravimetrically determined evaporation rates of volatile model compounds. The results show model evaporation experiments with native CdCl2 and CdCl2 resulting from the reaction of CaCl2 with CdO. Cadmium was studied because it is a volatile toxic heavy metal and its thermal behavior is relevant in various waste-treatment and recycling processes.

Ａｒ‐Ｃｌ２‐Ｏ２雰囲気におけるＰｂＯ‐ＰｂＣｌ２の塩化および蒸発挙動

It is quite important to know the reactivity and behavior of Pb contained in steelmaking dust, or bottom ash and fly ash generated from municipal solid waste incineration process with chlorine. In the present study, chlorination and evaporation kinetics of PbO-PbCl2 melt have been investigated in Ar-Cl2-O2 atmosphere from 1023 to 1123K. The weight of PbO specimen increased first and then decreased in Ar-Cl2-O2 stream during experiments, which phenomena mean that produced PbCl2 by PbO chlorination formed liquid oxychloride phase of PbO-PbCl2 system and then PbCl2 evaporated. Increase of partial pressure of chlorine increased the initial chlorination rate, however no effect on the latter evaporation rate was observed. Decrease of maximal weight gain of specimen and the slight increase of evaporation rate were observed with increasing partial pressure of oxygen. Apparent activation energies of chlorination and evaporation of PbO-PbCl2 melt in the steady state were 35 kJ/mol and 156 kJ/mol, respectively. Evaporation rate of PbO-PbCl2 was also investigated at 1073K in Ar-O2 atmosphere, however the change of evaporation rate with changing partial pressure of oxygen was within experimental error. Measured evaporation rate strongly depended on the composition of melt. Composition dependency of evaporation rate estimated from the activity of PbCl2 for the PbO-PbCl2 system generally represented the same trend, however the measured evaporation rate was larger than estimated one in the whole composition range. This result indicates that the formation of oxychloride melt affects the evaporation rate. Chlorination mechanisms and removal efficiency of Pb by chlorination have been discussed based on the present results.

Water and Heat Balance during Flight in the Rose‐Colored Starling (Sturnus roseus)

Water imbalance during flight is considered to be a potentially limiting factor for flight ranges in migrating birds, but empirical data are scarce. We studied flights under controlled ambient conditions with rose-colored starlings in a wind tunnel. In one experiment, we measured water fluxes with stable isotopes at a range of flight speeds (9-14 m s(-1)) at constant temperature (15 degrees C). In a second experiment, we measured evaporation rates at variable ambient temperatures (Ta = 5 deg -27 deg C) but constant speed (12 m s(-1)). During all flights, the birds experienced a net water loss. On average, water influx was 0.98 g h(-1) (SD = 0.16; n = 8), and water efflux was 1.29 g h(-1) (SD = 0.14; n = 8), irrespective of flight speed. Evaporation was related to temperature in a biphasic pattern. At temperatures below 18.2 degrees C, net evaporation was constant at 0.36 g h(-1) (SD = 0.18; n = 10), rising at higher temperatures with a slope of 0.11 per degree to about 1.5 g h(-1) at 27 degrees C. We calculated the relative proportion of dry and evaporative heat loss during flight. Evaporative heat loss at Ta < 18.2 deg C was 14% of total heat production during flight, and dry heat loss accounted for 84%. At higher temperatures, evaporative heat loss increased linearly with T(a) to about 25% at 27 degrees C. Our data suggest that for prolonged flights, rose-colored starlings should adopt behavioral water-saving strategies and that they cannot complete their annual migration without stopovers to replenish their water reserves.

Evaporation and land surface energy budget at the Salar de Atacama, Northern Chile

Playa systems are driven by evaporation processes, yet the mechanisms by which evaporation occurs through playa salt crusts are still poorly understood. In this study we examine playa evaporation as it relates to land surface energy fluxes, salt crust characteristics, groundwater and climate at the Salar de Atacama, a 3000 km 2 playa in northern Chile containing a uniquely broad range of salt crust types. Land surface energy budget measurements were taken at eight representative sites on this playa during winter (August 2001) and summer (January 2002) seasons. Measured values of net all-wave radiation were highest at vegetated and rough halite crust sites and lowest over smooth, highly reflective salt crusts. Over most of the Salar de Atacama, net radiation was dissipated by means of soil and sensible heat fluxes. Dry salt crusts tended to heat and cool very quickly, whereas soil heating and cooling occurred more gradually at wetter vegetated sites. Sensible heating was strongly linked to wind patterns, with highest sensible heat fluxes occurring on summer days with strong afternoon winds. Very little energy available at the land surface was used to evaporate water. Eddy covariance measurements could only constrain evaporation rates to within 0.1 mm d −1, and some measured evaporation rates were less than this margin of uncertainty. Evaporation rates ranged from 0.1 to 1.1 mm d −1 in smooth salt crusts around the margin of the salar and from 0.4 to 2.8 mm d −1 in vegetated areas. No evaporation was detected from the rugged halite salt crust that covers the interior of the salar, though the depth to groundwater is less than 1 m in this area. These crusts therefore represent a previously unrecorded end member condition in which the salt crusts form a practically impermeable barrier to evaporation.

Chlorination and Evaporation Behaviors of PbO-PbCl2 System in Ar-Cl2-O2 Atmosphere

It is quite important to know the reactivity and behavior of Pb contained in steelmaking dust, or bottom ash and fly ash generated from municipal solid waste incineration process with chlorine. In the present study, chlorination and evaporation kinetics of PbO-PbCl2 melt have been investigated in Ar-Cl2-O2 atmosphere from 1023 to 1123 K. The weight of PbO specimen increased first and then decreased in Ar-Cl2-O2 stream during experiments, which phenomena mean that produced PbCl2 by PbO chlorination formed liquid oxychloride phase of PbO-PbCl2 system and then PbCl2 evaporated. Increase of partial pressure of chlorine increased the initial chlorination rate, however no effect on the latter evaporation rate was observed. Decrease of maximal weight gain of specimen and the slight increase of evaporation rate were observed with increasing partial pressure of oxygen. Activation energies of chlorination and evaporation of PbO-PbCl2 melt in the steady state were 35 kJ/mol and 156 kJ/mol, respectively. Evaporation rate of PbO-PbCl2 was also investigated at 1073 K in Ar-O2 atmosphere, however the change of evaporation rate with changing partial pressure of oxygen was within experimental error. Measured evaporation rate strongly depended on the composition of melt. Composition dependency of evaporation rate estimated from the activity of PbCl2 for the PbO-PbCl2 system generally represented the same trend, however the measured evaporation rate was larger than estimated one in the whole composition range. This result indicates that the formation of oxychloride melt affects the evaporation rate. Chlorination mechanisms and removal efficiency of Pb by chlorination have been discussed based on the present results.

EFFECT OF PAN DIAMETER ON EVAPORATION AND REFERENCE CROP EVAPOTRANSPIRATION

The effect of pan size on evaporation rates, pan coefficient, and reference crop evapotranspiration is not clearlyunderstood. Evaporation rates (mm/day) were therefore measured using the standard class A pan, a half-standard pan (halfthe diameter of the class A pan), and quarter-standard pan between February 1 and April 30, 2000, at St. Augustine, Trinidad.Evaporation rates were highest in the quarter-standard pan, followed by the half-standard and then the standard pan. Heattransfer analysis showed that while the total heat absorbed by the water in the pans increased, the resulting total heat absorbedper surface area decreased with increasing pan diameter, thereby explaining the trend in the measured evaporation rates. Measuredevaporation rates from each pan were correlated with reference crop evapotranspiration rates predicted with the Penman-Monteith formula. This article demonstrates that pans smaller than the class A could be used to measure evaporation rates,provided that calibrations are carried out to determine the pan coefficients relating measured evaporation rates to evapotranspirationrates. This would result in substantial cost reductions in situations where a dense evaporation network is needed.

Effect of pressure on the rate of evaporation from capillaries: statistical rate theory approach

Statistical rate theory (SRT) leads to an expression for the evaporation rate that is in terms of independently determined parameters. A series of experiments have been conducted in which water evaporated from capillaries closed at one end and partially filled to different heights. From the measured evaporation rate, the SRT prediction of the vapor-phase pressure was compared with that determined by an independent technique. When the assumptions used in this technique were valid, the value of the pressure predicted from SRT and from this technique differed by only 0.004 Pa.

Study of the CdS crystal evaporation kinetics by laser step atomic photoionization

Laser resonant multistep atomic photoionization is employed to measure evaporation rates and saturated vapor pressures of cadmium sulfide and pure cadmium in temperature ranges of 585–950 and 350–535 K, respectively. It is shown that CdS thermally dissociates into Cd atoms and S2 molecules. The photoionization of cadmium atoms follows the scheme $$5s^1 S_0 \xrightarrow{{\lambda _1 = 326.1nm}}5p^3 P_1 \xrightarrow{{\lambda _2 = 479.9nm}}6s^3 S_1 \xrightarrow{{\lambda _3 = 488.1nm}}17p^3 P_2 + (\varepsilon = 12kV/cm) \to Cd^ + + e^ - .$$ .

Effect of inter-particle interactions on evaporation of droplets in a linear array

Effects of interparticle interactions on evaporation have been examined on droplets in a linear array generated by a modified vibrating orifice aerosol generator (VOAG). The size as well as the spacing between the droplets was varied by modulating the frequency of the generator, and the liquid flow rate through the orifice. Ethanol and methanol droplets of differing initial sizes and spacings were studied, and the instantaneous evaporation rates as well as droplet temperatures were measured using a resonance-based light scattering technique. The results show that at a fixed dimensionless spacing between the droplets (i.e., the ratio of the spacing to the droplet radius, l/ a), the size and temperature versus time data are highly reproducible. The measured evaporation rates were normalized by the evaporation rates of an isolated droplet under identical conditions to obtain the interaction parameter ( η) as a function of the dimensionless spacing between the droplets. The value of η was observed to decrease with a decrease in l/ a as predicted by the theoretical models, and as expected, found to be the same for ethanol and methanol droplets.

Even−Odd Alternation of Evaporation Rates and Vapor Pressures of C3−C9 Dicarboxylic Acid Aerosols

Aliphatic straight-chain dicarboxylic acids have been identified as common water-soluble organic components of atmospheric aerosols. To model the partitioning of such compounds between gas and particle phase in the atmosphere, information about their vapor pressures is essential. In this work, vapor pressures of C3−C9 dicarboxylic acids are derived from measured evaporation rates of submicron aerosols over the temperature range of 290−314 K using the tandem differential mobility analyzer technique. Vapor pressures obtained from the experimental data were as follows: log( , Pa) = − 4822 K/T + 12.9, log( , Pa) = − 7196.8 K/T + 19.8, (296 K) = 6.7 × 10-4 Pa, log( , Pa) = −8065.0 K/T + 22.2, log( , Pa) = −7692.8 K/T + 21.8, log( , Pa) = −9629.4 K/T + 26.5, and log( , Pa) = −7968.7 K/T + 21.7. Vapor pressures of C3−C9 dicarboxylic acids are shown to alternate strongly with the parity of the number of carbon atoms. Higher vapor pressures of the odd acids fit the less stable crystal structure, the propensity of...

Evaporation rate as a function of water salinity

Water evaporation is an important physical phenomenon that occurs in nature and in several industrial applications. Many researchers are working in this area to establish a good correlation that can be used to measure evaporation rates precisely. In this article, we review previous experience by describing the instrument used, method of measurement, conditions of experimentation and correlations resulting from these experiments. Then, an experimental test that was constructed to measure the evaporation rates of distilled water, seawater (34,000 ppm) and two brine solutions with different salinities (56,000 and 69,000 ppm) is presented. A new correlation for measuring evaporation rate was established taking into account the effect of salinity on evaporation rate, which was not done by any other investigator before. Finally, a comparison is made between our correlation and a previous one for distilled water. The results show a decrease in the evaporation rate with an increase of the water salinity because of the reduction in the water vapor pressure at the water surface.