Evaporation Experiments Research Articles

Ring droplet formation during evaporation of a sessile water droplet on a biphilic surface

Numerous studies have investigated droplet evaporation on surfaces with different roughness and wettability values. However, most studies have focused on droplet evaporation from homogeneous surfaces at low surface temperatures (below 100 °C). In this study, we conducted droplet evaporation experiments on biphilic surfaces with different ring pattern sizes fabricated by a hybrid method consisting of the sol-gel approach and a picosecond laser system. This study investigated the droplet evaporation boiling phenomenon on these biphilic surfaces under superheated conditions. Changes in droplet geometry and inner bubble dynamics during evaporation were analyzed using a high-speed camera. A ring-shaped droplet formed during the final evaporation period. The formation of the ring enhanced the droplet evaporation efficiency. Furthermore, the experimental results from this study work were compared with the theoretical model proposed in the literature.

Intensifying Solar Interfacial Heat Accumulation for Clean Water Generation Excluding Heavy Metal Ions and Oil Emulsions

Solar‐driven interfacial steam generation has emerged as an innovative technique for seawater desalination due to its high photothermal conversion efficiency and potential industrial applications. Herein, a superior interfacial heat accumulation structure composed of semiconductive in situ polymerization (polypyrrole) of nickel foam (IPNF) is reported. The IPNF photothermal layer is assembled with superhydrophilic polyurethane substrate for synchronous water transport and excellent thermal insulation. The 2D ultrablack mesh induces multiple incident rays within the diffused polymerized surface, which allows omnidirectional solar absorption (88.5 %) and intensifying heat localization (49.5 °C @ 1 sun). The state‐of‐the‐art evaporation performances reveal that the integrated IPNF solar evaporator exhibits an excellent evaporation rate (1.74 kg m−2 h−1) and solar‐to‐vapor conversion efficiency (90% excluding heat losses) under 1 kW m−2 solar intensity. Besides this, the long‐term evaporation experiments show negligible discrepancy under seawater conditions (13.27 kg m−2/8 h under 1 kW m−2) and engrain its functioning potential for multimedia and salt rejection (3.2 g × NaCl/240 min). More importantly, herein, insights into different water states in the polymeric network systems during solar‐driven evaporation are provided. This work shows a significant potential to generate freshwater excluding heavy metals and other oil emulsions for industrial applications.

Salt-tolerant and low-cost flame-treated aerogel for continuously efficient solar steam generation

Interface solar-driven evaporation is a very promising technology used in solar energy harvesting, seawater desalination and water purification. However, salt accumulation is still a serious problem that hinders the long-term stable operation of the evaporator. Herein, we use natural wood with inherent porosity to develop a flexible cellulose aerogel, which can be used as efficient and stable solar evaporator for desalination after simple surface carbonization. This aerogel evaporator achieves a solar steam efficiency of 83.4% and an evaporation rate of 1.40 kg m−2 h−1 under the sunlight intensity of 1 kW m−2. In the simulated evaporation experiment for 7 days, the evaporator shows a stable evaporation rate (about 1.39 kg m−2 h−1), indicating the potential for long-term operation. In addition, the evaporator has the ability to resist salt accumulation and self-cleaning. The low cost, simple preparation and multiple functions make the evaporator promising to be a continuous and stable installation for solar desalination.

Near infrared triggered dual-functional NaYF4:Yb3+/Tm3+@NaYF4:Yb3+/Sm3+ core-shell UCNPs for temperature sensing and photothermal conversion

Upconversion core-shell nanoparticles with dual-function of temperature sensing and photothermal conversion are preferable in diagnose and treatment of cancer. Herein, NaYF4:Tm3+/Yb3+@NaYF4:Sm3+/Yb3+ upconversion nanoparticles have been synthesized by a high-temperature thermal decomposition method. XRD and TEM are used to characterize the crystal structure and morphology of the samples. Temperature dependent upconversion spectra are measured under excitation of 980 nm within the scope of 303–498 K. The investigation on temperature sensing properties are on the basis of the luminescence intensity ratio of Tm3+. The designed core shell nanoparticles and bare core nanoparticles both have good temperature sensing performances, and the sensing properties of both are similar. Furthermore, the photothermal conversion performances are investigated ground on the power dependent temperature measurement, ethanol evaporation experiment and visual infrared thermal images. It is found that the photothermal conversion ability of the core-shell UCNPs is greatly improved by coating of the NaYF4: Sm3+/Yb3+ outer shell.

Experimental Study on the Synergistic Effect between Evaporation Weathering and Emulsification of Oil Spills

First, a range of experiments using a stainless steel shallow plate in a thermostatic oscillator were carried out to simulate evaporation weathering of oil spills under different temperatures, wind velocities, oil film thicknesses, and wave conditions. The information on influencing factors of evaporation weathering could be obtained. Then, evaporation experiments of four oil samples with three emulsification states were conducted, and the effect of emulsification on evaporation of oil spills was investigated. The characteristics of each operation were described, mass loss characteristics of oil spills with time were plotted, and the effects of evaporative weathering processes under different conditions were quantitatively compared. A high-precision visualization system was utilized to simulate experimentally oil spill emulsification processes, and the effect of evaporative weathering on emulsification weathering of oil spills was investigated. The results of evaporation experiments showed that the increase of temperature could promote the evaporative weathering. The thin film thickness was beneficial to evaporation of oil spills. The increment of the wind speed could promote evaporation behavior when the wind velocity was small, but the increase of velocity had little effect on oil evaporation when the wind speed was large. Wave conditions had little effect on oil evaporation under the conditions of this experiment. The effect of different emulsification states on oil evaporation was not consistent. Unstable or semistable water-in-oil emulsions inhibited oil evaporation at the initial stage of evaporation, but water evaporation would increase oil-phase evaporation with the destruction of the emulsion structure. Stable water-in-oil emulsions inhibited evaporation weathering. The evaporation weathering of oil was conducive to the emulsification of oil.

Assessment of the statistical rate theory expression for evaporation mass flux

A series of 72 steady-state evaporation experiments in which water evaporated from a spherical liquid-vapor interface have been conducted. In each experiment, the interfacial temperatures, the temperature profile across the liquid-vapor interface, and the pressure in the vapor phase were measured. When the interfacial parameters were used in the statistical rate theory (SRT) expression for evaporation flux, the vapor-phase pressure could be predicted to a reasonable degree of accuracy in all experiments. In all 72 experiments, the interfacial temperature of the vapor was always higher than that of the liquid phase and in certain cases, the difference was measured to be 7.1 K. Measurement of the vapor-phase pressure near the cool liquid-vapor interface and far from the interface did not show a significant difference, indicating that the density (concentration) in the bulk vapor phase may not be uniform.

First-year cover crop effects on the physical and hydraulic properties of the surface layer in a loamy soil

Soil degradation is a global problem, threating its conservation and affecting agronomic production. No-tillage (NT) is the main management system for soil conservation world-wide. However, in Argentina, simplification of the crop sequence with high proportion of soybean under NT is a very common practice, leading to soil physical constrains. Crop sequence intensification through the inclusion of cover crops has been reported as an effective tool in the long-term for the enhancement of ecosystems services, improving NT performance. The objective of this work was to follow the evolution of the structural pore domain in the surface layer during the first year after the incorporation of cover crop (cover fallow of barley (Hordeum vulgare L.) and vetch (Vicia sp. L.), CF), as compared with bare fallow (BF), under NT management in a field experiment located in the Argentinean Depressed Pampas Region. Mini-infiltration and evaporation experiments were conducted in undisturbed soil samples (0−5 cm depth) in the laboratory in order to determine the pore size distribution (PoSD) and hydraulic conductivity (K (h)) functions in three different dates (after cover crop seeding, after maize seeding and before maize harvest) in order to follow the changes in soil pore functioning during the first year of cover cropping management. Changes in the soil pore functioning were observed in the short-term after the first cover crop cycle, showing the time-dependence of the hydraulic soil properties. These changes were mainly observed during the maize cycle. Under CF an increment of structural porosity (PS) was observed at the end of the maize crop cycle, while during the fallow period this variable remained relatively constant. K (h) and structural porosity connectivity (Cw) showed a rapid increment under BF during the fallow period, while under CF the increase was more gradual, which could be related to pore clogging and roots decay cycles. From the obtained results, we found that the introduction of cover crops under NT promotes the increment of a secondary pore system related to structural soil porosity during the first year and enhances the unsaturated hydraulic conductivity and pore connectivity, especially at the end of the summer crop cycle. Our results highlight the importance of including cover crops into the crop rotation to improve the structural porosity and its connectivity. As well, the results show the necessity of including the short-term changes in the study of soil hydraulics properties.

Experimental Research on the Disruptive Evaporation and the Motion Characteristics of Secondary Droplets for Emulsified Biodiesel with a Suspended Droplet Configuration.

The secondary atomization of droplets is one of the means to improve the efficiency of diesel fuel injection atomization. As a promising biomass fuel, emulsified biodiesel showed a good prospect in improving the atomization effect of diesel engines. In this study, a high-temperature and pressure-resistant evaporator was designed to simulate diesel-like conditions, and the evaporation and combustion experiments of emulsified biodiesel droplets were carried out. The morphological changes in the droplets were dynamically captured using a high-speed camera. According to the collected images, the evaporation characteristic parameters, the dynamic parameters of droplet motion, and the correlation between the original and secondary droplets were quantitatively analyzed. The gain effect of secondary atomization for droplets on the diesel engine spray was evaluated. The results showed that the emulsified biodiesel underwent nucleation, agglomeration, puffing, and explosion during the evaporation process, while the classic d2 law only meets a few cases of this fuel. The effect of high temperature was reflected in reducing the normalization time of droplet agglomeration and explosion, while the higher pressure inhibited the expansion of the droplets, thus slowing down the expansion rate and restricting the droplet volume. Driven by the water content, the time of droplet explosion was closer to the droplet lifetime. The evaporation process of the secondary droplet was similar to that of the original droplet over a reduced scale of 1–2 orders of magnitude. (Dd/Dd0)2 ≈ 1 was a necessary condition for the secondary droplets to be produced in large quantities. The average equivalent diameter of the droplets was distributed in the range of 80–140 μm, and the secondary atomization caused expansion of the spray range by 20–40%. Expansion of the range of secondary droplets was beneficial to shortening the ignition delay and increasing the combustion rate.

Effects of different biomass materials as a salt-isolation layer on water and salt migration in coastal saline soil.

The aim of this study was to find a material suited for the prevention of evaporative water loss and salt accumulation in coastal saline soils. One-dimensional vertical water infiltration and phreatic evaporation experiments were conducted using a silty loam saline soil. A 3-cm-thick layer of corn straw, biochar, and peat was buried at the soil depth of 20 cm, and a 6-cm-thick layer of peat was also buried at the same soil depth for comparison. The presence of the biochar layer increased the upper soil water content, but its ability to inhibit salt accumulation was poor, leading to a high salt concentration in the surface soil. The 3-cm-thick straw and 6-cm-thick peat layers were most effective to inhibit salt accumulation, which reduced the upper soil salt concentration by 96% and 93%, respectively. However, the straw layer strongly inhibited phreatic evaporation and resulted in low water content in the upper soil layer. Compared with the straw layer, the peat layer increased the upper soil water content. Thus, burying a 6-cm-thick peat layer in the coastal saline soil is the optimal strategy to retain water in the upper soil layer and intercept salt in the deeper soil layer.

Sedimentation sequence of a high-temperature silica-rich hot spring: evidence from isothermal evaporation experiments and from petrology and mineralogy of sinters

Sedimentation sequence of a high-temperature silica-rich hot spring: evidence from isothermal evaporation experiments and from petrology and mineralogy of sinters

Capillary, Film, and Vapor Flow in Transient Bare Soil Evaporation (2): Experimental Identification of Hydraulic Conductivity in the Medium to Dry Moisture Range

AbstractBare‐soil evaporation involves coupled flow of liquid water, water vapor, and heat. As evaporation results in non‐isothermal conditions in the soil, the temperature dependence of transport properties and thermal fluxes of water and vapor must be accounted for. In a companion paper, we showed that the Richards equation, that is, a single‐phase flow model assuming isothermal conditions, is applicable to accurately determine soil hydraulic properties including the medium to dry range from evaporation experiments by inverse modeling. This is warranted if pressure head data across a wide moisture range, that is, from almost saturated to almost air‐dry, are used in the objective function and a suitable parameterization of the hydraulic conductivity function including vapor and non‐capillary flow is used. In this article, we confirm the theoretical results by examining real evaporation experiments, in which we measured the temporal dynamics of evaporation rate, soil temperature, and pressure head in laboratory soil columns. Pressure head was measured with mini‐tensiometers and relative humidity sensors. The measurements were evaluated by inverse modeling with the Richards equation assuming isothermal conditions and ambient temperature in the soil. Our results for a sandy and a loamy soil show that the observed transient water and vapor dynamics in the drying soil could be accurately matched, provided the hydraulic conductivity curve considered isothermal vapor diffusion and film flow. These components dominate hydraulic conductivity in the medium to dry soil moisture range and were uniquely identified in agreement with the theoretical analysis in the companion article.

Capillary, Film, and Vapor Flow in Transient Bare Soil Evaporation (1): Identifiability Analysis of Hydraulic Conductivity in the Medium to Dry Moisture Range

AbstractEvaporation experiments are frequently used to determine soil hydraulic properties. We simulated laboratory evaporation experiments with a coupled water, vapor, and heat flow model which includes the surface energy balance. The simulations are performed with different parametrizations of soil hydraulic properties with a focus on soil hydraulic conductivity in medium to dry soil. In previous studies, conductivity in this moisture range has been shown to be influenced not only by water flow in completely filled capillaries (“capillary flow”) but also by film and corner flow (“film flow”). Our forward simulations highlight the strong influence of an increased conductivity caused by film flow on evaporation rate, cumulative water loss, soil temperature, and soil water pressure head during evaporation. Film flow extends the duration of stage‐1 evaporation and increases the evaporation rate during stage‐2 even if all other physical material properties are the same. The simulated data were used in inverse simulations with the Richards equation to test whether soil hydraulic properties can be identified without bias. This is a priori questionable because the Richards equation is an isothermal flow model and simplifies the true physics considerably, by ignoring thermal liquid and thermal vapor fluxes, as well as temperature effects on the hydraulic properties. Our results show that the identification of the water retention and hydraulic conductivity curves is bias‐free for media with and without film flow. We conclude that the Richards equation can be safely used to identify hydraulic properties from evaporation experiments by inverse modeling.

Volatile organic compound emissions from solvent- and water-borne coatings – compositional differences and tracer compound identifications

Abstract. The emissions of volatile organic compounds (VOCs) from volatile chemical products (VCPs) – specifically personal care products, cleaning agents, coatings, adhesives, and pesticides – are emerging as the largest source of petroleum-derived organic carbon in US cities. Previous work has shown that the ambient concentration of markers for most VCP categories correlates strongly with population density, except for VOCs predominantly originating from solvent- and water-borne coatings (e.g., parachlorobenzotrifluoride (PCBTF) and Texanol®, respectively). Instead, these enhancements were dominated by distinct emission events likely driven by industrial usage patterns, such as construction activity. In this work, the headspace of a variety of coating products was analyzed using a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS) and a gas chromatography (GC) preseparation front end to identify composition differences for various coating types (e.g., paints, primers, sealers, and stains). Evaporation experiments of several products showed high initial VOC emission rates, and for the length of these experiments, the majority of the VOC mass was emitted during the first few hours following application. The percentage of mass emitted as measured VOCs (<1 % to 83 %) mirrored the VOC content reported by the manufacturer (<5 to 550 g L−1). Ambient and laboratory measurements, usage trends, and ingredients compiled from architectural coatings surveys show that both PCBTF and Texanol account for ∼10 % of the total VOC ingredient sales and, therefore, can be useful tracers for solvent- and water-borne coatings.

Experimental study on the coupled behavior of dynamic cracking and moisture-heat evolution of a clay under evaporation

A clay is prone to shrinkage and cracking under evaporation, which can cause vast hazards in geotechnical and geo-environmental engineering. Knowledge of the coupled behavior of dynamic cracking and moisture-heat evolution is helpful for better understanding the mechanical performance of a clay under evaporation. An evaporation experiment was conducted on a clayey soil specimen in this study, accompanied by observation of shrinkage and cracking and monitoring of moisture-heat. In this way, the fully coupled behavior of shrinkage, cracking, and moisture-heat evolution of the clay under evaporation was investigated. The results show that the clay loses most of its water and achieves most of the shrinkage before the latter evaporation stage. Especially in the intermediate evaporation stage, the soil saturation has a quick reduction, the soil suction has a linear increase, and the soil temperature has a sharp rise. Because of this moisture-heat evolution, both the degree of the nonuniform shrinkage and the increased rate of the crack ratio and the crack depth reach the maximum values. Along with the crack developing downward and bringing new air-entry channels, the actual evaporation front also moves downward. The evaporation from the surface-exposed crack can significantly affect the moisture-heat evolution of the clay. The crack can develop further to the width and the depth owing to the nonuniform shrinkage existing at the different locations and the different depths of the clay. The nonuniform shrinkage may be attributed to the heterogeneity of the soil properties, the inhomogeneous evaporation environment, and the huge difference of moisture-heat characteristics of the clay.

Continuous and simultaneous measurement of triple-oxygen and hydrogen isotopes of liquid and vapor during evaporation experiments.

Oxygen and hydrogen isotopes are important tools for studying the modern and past hydrological cycle. Previous evaporation experiments used episodic measurement of liquid and/or vapor or did not measure all isotopologues of water. Here, we describe an evaporation experimental system that allows all isotopologues of liquid and water vapor to be measured simultaneously and near-continuously at high precision using cavity ring-down laser spectroscopy (CRDS). Evaporating liquid is periodically sampled from a closed recirculating loop by a syringe pump that delivers a constant supply of water to the vaporizer, achieving a water vapor concentration of 20,000 ppmV H2 O (±132, 1σ). Vapor is sampled directly from the evaporation chamber. Isotope ratios are measured simultaneously with a Picarro L2140-i CRDS instrument. For liquid measurements, Allan variance analysis indicates an optimum data collection window of 34 min for oxygen isotopes and 27 min for hydrogen isotopes. During these periods, the mean standard error is ±0.0081‰ for δ17 O values, ±0.0081‰ for δ18 O values, and ±0.019‰ for δ2 H values. For the derived parameters 17 O-excess and d-excess, the standard error of the mean is 5.8 per meg and 0.07‰, respectively. For the vapor phase a 12.5 min data window for all isotopologues results in a mean standard error of ±0.012‰ for δ17 O values, ±0.011‰ for δ18 O values, and ±0.023‰ for δ2 H values. For the derived parameters, the standard error of the mean is 9.2 per meg for 17 O-excess and 0.099‰ for d-excess. These measurements result in consistently narrow 95% confidence limits for the slopes of ln(δ17 O + 1) vs ln(δ18 O + 1) and ln(δ2 H + 1) vs ln(δ18 O + 1). The experimental method permits measurement of fractionation of triple-oxygen and hydrogen isotopes of evaporating water under varying controlled conditions at high precision. Application of this method will be useful for testing theoretical models of evaporation and conducting experiments to simulate evaporation and isotopic equilibration in natural systems.

Experimental Study on Evaporation Characteristics of Light Cycle Oil Droplet under Various Ambient Conditions

The authors conducted droplet evaporation experiments of light cycle oil (LCO) at various ambient temperatures and pressures. Five kinds of LCO and three kinds of arranged fuels were used. We investigated the evaporation characteristics of LCO and the relationships between the evaporation characteristics and the cetane index. In addition to that, a surrogate fuel composed of four chemical species, which can simulate the droplet evaporation characteristics of LCO, was suggested. Experimental results show that the differences in droplet lifetime between fuel species become larger with decreasing ambient temperature. This is because the low volatile component made the evaporation rate outstandingly slow at a low ambient temperature. It was found that the relationship between droplet lifetime and the late-stage distillation temperature becomes stronger at low ambient temperature and high ambient pressure. By an analysis employing the properties of chemical species in LCO surrogate fuel, it is clarified that the mass evaporation rate becomes smaller than the internal diffusion, which is the condition similar to that in the distillation test. Finally, the relationship between the droplet lifetime and the cetane index was investigated. It can be concluded that the droplet lifetime is independent of the cetane index under all conditions tested in this study. The experimental data obtained by this research can be utilized for the validation of multicomponent fuel droplet evaporation models in the future.

Triple oxygen isotope systematics of evaporation and mixing processes in a dynamic desert lake system

Abstract. This study investigates the combined hydrogen deuterium and triple oxygen isotope hydrology of the Salar del Huasco, an endorheic salt flat with shallow lakes at its centre that is located on the Altiplano Plateau, N Chile. This lacustrine system is hydrologically dynamic and complex because it receives inflow from multiple surface and groundwater sources. It undergoes seasonal flooding, followed by rapid shrinking of the water body at the prevailing arid climate with very high evaporation rates. At any given point in time, ponds, lakes, and recharge sources capture a large range of evaporation degrees. Samples taken between 2017 and 2019 show a range of δ18O between −13.3 ‰ and 14.5 ‰, d-excess between 7 ‰ and −100 ‰, and 17O-excess between 19 and −108 per meg. A pan evaporation experiment conducted on-site was used to derive the turbulence coefficient of the Craig–Gordon isotope evaporation model for the local wind regime. This, along with sampling of atmospheric vapour at the salar (-21.0±3.3 ‰ for δ18O, 34±6 ‰ for d-excess and 23±9 per meg for 17O-excess), enabled the accurate reproduction of measured ponds and lake isotope data by the Craig–Gordon model. In contrast to classic δ2H–δ18O studies, the 17O-excess data not only allow one to distinguish two different types of evaporation – evaporation with and without recharge – but also to identify mixing processes between evaporated lake water and fresh flood water. Multiple generations of infiltration events can also be inferred from the triple oxygen isotope composition of inflow water, indicating mixing of sources with different evaporation histories. These processes cannot be resolved using classic δ2H–δ18O data alone. Adding triple oxygen isotope measurements to isotope hydrology studies may therefore significantly improve the accuracy of a lake's hydrological balance – i.e. the evaporation-to-inflow ratio (E / I) – estimated by water isotope data and application of the Craig–Gordon isotope evaporation model.

Investigation on Switchable Evaporation and Condensation Horizontal Single Tube Heat Exchange Experiment Platform

In this experiment, the switchable evaporation and condensation horizontal single-tube heat exchange experiment platform is designed. And the equipment selection and construction of the experiment platform is completed through the design calculation. The experimental results show that the thermal balance error of the test section of the experiment platform is less than 15%, especially the condensation and evaporation experiment of R22 in 12.7 mm copper tube, and the evaporation experiment of R410A in 9.52 mm copper tube, the thermal balance error of the experiment is less than 5%. The experiment platform can realize heat exchange experiments with different refrigerants, and the test section of the experiment platform can be standardized replacement of tube types according to research needs.

Sustainable self-cleaning evaporator for long-term solar desalination using gradient structure tailored hydrogel

Interfacial solar evaporation has been demonstrated as a promising strategy to mitigate water scarcity. However, for practical application in marine environment, the accumulation of salt and growth of microorganisms such as bacteria will cause scarring and fouling of the evaporators, depressing the potential for long-term sustainable use. Here, we report a hydrogel evaporator (chitosan/PAAm/PPy) with integrated three-layer structure containing individual functions for heat localization to improve solar evaporation efficiency, salt redissolution and antibacterial growth for sustainable long-term use, as well as management of thermal energy loss, respectively. The as-fabricated hydrogel evaporator presented a high-water evaporation rate of 2.41 kg m-2h−1 under 1-sun illumination, and excellent self-cleaning property against the salt accumulation and bacteria growth. During a two-week continuous evaporation experiment in simulated marine water with 3.5 wt% salinity and mixture of bacteria, the evaporator generated vapor stably in a range of 2.30 ~ 2.41 kg m-2h−1, without noticeable performance decay. Additionally, the hydrogel evaporator shows a stable vapor generation rate during cycled dehydration-hydration processes, as well as against repeated weight loading–unloading tests, indicating its convenience for long-term use and storage.

Evaporating droplets on inclined plant leaves and synthetic surfaces: Experiments and mathematical models

HypothesisEvaporation of surfactant droplets on leaves is complicated due to the complex physical and chemical properties of the leaf surfaces. However, for certain leaf surfaces for which the evaporation process appears to follow the standard constant-contact-radius or constant-contact-angle modes, it should be possible to mimic the droplet evaporation with both a well-chosen synthetic surface and a relatively simple mathematical model. ExperimentsSurfactant droplet evaporation experiments were performed on two commercial crop species, wheat and capsicum, along with two synthetic surfaces, up to a 90° incline. The time-dependence of the droplets’ contact angles, height, volume and contact radius was measured throughout the evaporation experiments. Mathematical models were developed to simulate the experiments. FindingsWith one clear exception, for all combinations of surfaces, surfactant concentrations and angles, the experiments appear to follow the standard evaporation modes and are well described by the mathematical models (modified Popov and Young–Laplace-Popov). The exception is wheat with a high surfactant concentration, for which droplet evaporation appears nonstandard and deviates from the diffusion limited models, perhaps due to additional mechanisms such as the adsorption of surfactant, stomatal density or an elongated shape in the direction of the grooves in the wheat surface.