Evaporation Measurements Research Articles

Water spray for pre-cooling of inlet air for Natural Draft Dry Cooling Towers – Experimental study

This paper deals with an experimental investigation of inlet air pre-cooling with water sprays aimed to enhance the performance of Natural Draft Dry Cooling Towers during high ambient temperature periods. An open-circuit wind tunnel with a test section of 1 × 1 m2 cross section and length of 5.2 m was employed to represent an inlet flow area section in a Natural Draft Cooling Tower. Experimental measurements of droplet evaporation and air cooling are presented. Nine high pressure, hollow cone nozzles were tested at various droplet sizes, air velocities (1, 2, 3 m/s), and injection rates under different ambient conditions. The water spray was characterized using a Phase Doppler Particle Analyser (PDPA). The effects of drop size distribution and air velocity on droplet evaporation, cooling effectiveness, and coverage area were investigated. The data shows clear trends of cooling enhancement with low air velocity or small droplet size distribution. It was found that the spray cooling efficiency, to a large extent, is dependent on spray coverage area. The experimental findings will benefit optimizing spray cooling performance in Natural Draft Dry Cooling Towers and nozzle arrangement.

Sensory and sympathetic disorders in chronic non-specific neck pain.

The signs of sympathetic and sensory nerve-related disorders are not widely investigated in chronic nonspecific neck pain (NNP) patients. Thus, we performed skin temperature (Tsk), evaporation and touch threshold (TT) measurements to reveal possible dysfunctions at the fingertips of NNP patients (n=60) compared with healthy controls (n=11). Neck pain intensity was the main modifier of Tsk, and age the main modifier of TT in a multivariate model. On comparisons of the subgroups of NNP patients with unilateral (n=26) and bilateral (n=34) symptoms and controls, TT differed and Tsk tended to differ, the unilateral pain patients being found to demonstrate higher TT values on both sides. Interrelations between the measured parameters were found in the controls, but not in the patients. The NNP patients exhibited signs of functional impairment of innervation reflected in changes in tactile sensitivity and vasoactive sympathetic function. These changes may be based on both central and peripheral mechanisms, which possibly differ in patients with unilateral and bilateral symptoms.

Evaluación al sistema alternativo de evaporación forzada para lixiviados provenientes del botadero a cielo abierto de la ciudad de Estelí.

La realización de ésta investigación, permitió evaluar un sistema alternativo de tratamiento de los lixiviados generados en el botadero a cielo abierto de la ciudad de Estelí a partir de la evaporación forzada a través de un invernadero piloto tipo domo, en donde se demostró la viabilidad del sistema por la facilidad de las condiciones meteorológicas, permitiendo así una evaporación promedio de 0.78 cm/día y posteriormente la identificación de los gases y olores ofensivos emitidos por los lixiviados que estaban concentrados en el domo que luego de la estabilización estos olores son casi inapreciables, este monitoreo se realizó por veinte y dos días consecutivos. Del monitoreo de se logró determinar que el la temperatura para este lixiviado se encuentra en un rango de 26 º a 34 ºC con un valor promedio de 31º, siendo este rango de temperatura propio de un proceso anaerobio denominado Mesófilico. Se determinó la tendencia de los datos de evaporación de tipo exponencial. Es decir que a mayor altura de la lámina, menor es la evaporación esto se deduce debido a que se trabajó con dos láminas de lixiviados en el interior del domo, siendo la óptima de 20cm y la que se analiza en esta investigación. La implementación de éste proyecto, Evaluación al sistema alternativo de evaporación forzada para lixiviados provenientes del botadero a cielo abierto de la ciudad de Estelí; es un campo poco estudiado a nivel nacional, siendo ésta una oportunidad y técnica de investigación que puede llegar a permitir el uso de tecnologías económicas y amigables con el ambiente.

Inundation and groundwater dynamics for quantification of evaporative water loss in tropical wetlands

Abstract. Characterizing hydrological processes within tropical wetlands is challenging due to their remoteness, complexity and heterogeneity. In particular, estimates of evaporative water loss are inherently uncertain. In view of the large influence on the local and regional climate, the quantification of evaporation is essential for the determination of the water balance of permanent and intermittent water bodies. Data for tropical wetlands are scarce where their remoteness impedes direct evaporation measurements. Seasonal inundation dynamics affect evaporation processes in tropical wetlands, which can be analysed in two stages: the first stage during the wet season and the second stage during the dry season. As yet no adequate method exists for determining second-stage evaporation in a data-scarce environment that additionally allows for a transfer of simulated actual evaporation (AET) to other locations. Our study aimed at developing a process-based model to simulate first- and second-stage evaporation in tropical wetlands. We selected a set of empirical potential evaporation (PET) models of varying complexity, each based on different assumptions and available data sets, and evaluated the models with pan evaporation observations in the Pantanal of South America, one of the largest tropical wetlands in the world. We used high-resolution measurements of surface and groundwater levels at different locations to determine the water available for evaporation. AET was derived by constraining simulated PET based on available water. The model of best fit was applied to different types of water bodies with varying hydroperiods to capture first- and second-stage evaporation across a range of wetland types. With our new model we could quantify evaporative water loss in the dry and the wet season for different locations in the Pantanal. This new spatially explicit approach represents an improvement in our understanding of the role of evaporation in the water balance of the Pantanal. We recommend the application of this model in other remote tropical wetlands, since only a minimum of input data is necessary.

Hydro‐climatic variability and perturbations in Mexico's north‐western temperate forests

AbstractClimate variability and/or change control/s the local hydrologic cycle and consequently forest perturbations such as wildfires and bark beetle outbreaks. This case study addresses the following concerns: (a) the long‐term trends in precipitation, potential and actual evapotranspiration, run‐off, soil moisture content, number of wildfires, burned area, and bark beetle outbreaks and (b) the manner in which the fire occurrence, fire size, and beetle outbreaks are related to these hydrologic variables and multi‐decadal climate indices in Mexico's north‐western temperate forests. Using the daily measurements of precipitation and evaporation as well as the modelled interception loss and evapotranspiration, run‐off and soil moisture content were computed using a mass balance budget model. Mann–Kendall, linear regression, and autoregressive integrated moving averaging techniques were used to evaluate the statistical significance of monotonic trends on the first momentum for the monthly and annual time series of hydro‐climate (1945–2007), forest wildfire (1970–2012), and bark beetle infestation (1999–2012) data. The statistical analysis showed time series to be stationary in the first momentum. Recent wildfires and bark beetle population eruptions are associated with low modelled dry season soil moisture over several years. Drought spells, frosts, and pulses of high area burned, and high number of wildfires preceded acute discrete bark beetle population eruptions. Copyright © 2014 John Wiley & Sons, Ltd.

Groundwater dynamics under water-saving irrigation and implications for sustainable water management in an oasis: Tarim River basin of western China

Abstract. Water is essential for life. Specifically in the oases of inland arid basins, water is a critically limited resource, essential for the development of the socio-economy and the sustainability of eco-environmental systems. Due to the unique hydrological regime present in arid oases, a moderate groundwater table is the goal of sustainable water management. A shallow water table induces serious secondary salinization and collapse of agriculture, while a deep water table causes deterioration of natural vegetation. From the hydrological perspective, the exchange flux between the unsaturated vadose zone and groundwater reservoir is a critical link to understanding regional water table dynamics. This flux is substantially influenced by anthropogenic activities. In the Tarim River basin of western China, where agriculture consumes over 90% of available water resources, the exchange flux between the unsaturated vadose zone and groundwater reservoir is influenced strongly by irrigation. Recently, mulched drip irrigation, a sophisticated water-saving irrigation method, was widely applied in the Tarim River basin, which greatly impacted the exchange flux and thus the regional groundwater dynamics. Capitalizing on recent progress in evaporation measurement techniques, we can now close the water balance and directly quantify the exchange flux at the field scale, thus gaining a better understanding of regional groundwater dynamics. In this study, comprehensive observations of water balance components in an irrigated cropland were implemented in 2012 and 2013 in a typical oasis within the Tarim River basin. The water balance analysis showed that the exchange flux and groundwater dynamics were significantly altered by the application of water-saving irrigation. The exchange flux at the groundwater table is mostly downward (310.5 mm year−1), especially during drip irrigation period and spring flush period, while the upward flux is trivial (16.1 mm year−1) due to the moderate groundwater table depth (annual average depth 2.9 m). Traditional secondary salinization caused by intense phreatic evaporation (fed by upward exchange flux) is alleviated. However, a new form of secondary salinization may be introduced unwittingly if there is lack of water for periodic flushing, especially when brackish water is used in the irrigation. Furthermore, the water saved via drip irrigation has been used in further growth of irrigated lands instead of supporting the ecological system. This could lead to an increased risk of eco-environmental degradation and calls for improved governance schemes. The insights gained from this study can be potentially applied to other arid inland areas (e.g., central Asia) which face similar water shortages and human development problems.

First U-Pb data on age of granitoids in the basement of the Pechora basin

The Pechora basin, a large regional tectonic struc� ture in the Pechora region, is located between the Timan and Ural mountains (Fig. 1). Its section is com� posed of Upper Cambrian sedimentary-metamorphic and igneous rocks of the basement (Timanides) uni� versally overlain by a platformal cover represented by Ordovician-Cenozoic sedimentary and volcanic rocks. The basement comprises the Izhma, Pechora, and Bol'shezemel'skaya zones. The last two constitute the Bol'shezemel'skaya megablock, and the Izhma zone together with the Timan and Kanin Peninsula form the Timan megablock. According to geophysical and drilling data, the megablocks distinctly differ from each other in the composition and type of magmatism (7). The boundary between them corresponds to the zone of the NWextending Pripechora and Ilych- Chikshino deepseated faults. The thickness of the platformal cover varies from 4-7 km in central areas of the Pechora basin to 1-4 km in arches and uplifts. In this connection, information on the structure and geo� dynamic development of the basement beneath the basin is derived from the core of over 200 boreholes drilled with different purposes up to a depth of 5 km (7). Granitoids have been recovered by 26 boreholes throughout the entire region being more abundant in the Izhma and Pripechora-Ilych-Chikshino zones. Until the end of the 20th century, the age of granitoids was known from the limited K-Ar data (1, 13), most of which correspond to the period of 600-500 Ma. They provided grounds for assuming that granitoids are Vendian-Cambrian in age. Subsequently, geo� chronological dates were obtained by Pb-Pb (Pb evaporation) measurements in single zircon crystals from granites and diorites recovered from several drill� holes (13). These measurements yielded uniform ages in the interval of 567-551 Ma corresponding in the recent stratigraphic scale to the boundary of the Lower and Upper Vendian (12). The dating of zircons from igneous rocks using the radiogenic Pb isotopes is based on the assumption that the 207 Pb/ 206 Pb ratios (ages) remain unchanged after the formation of zircons and host rocks, although this is frequently not the case. The subsequent Rb-Sr investigations of granitoids from the Izhma and Pripechora-IlychChikshino zones (4) recovered by the same boreholes, where zir� con was analyzed, revealed that the Rb-Sr ages are confined to the period of 608-595 Ma, i.e., to the Riphean-Vendian boundary interval (12). These data are quite consistent with the ages obtained for grani� toid massifs in the North Timan structure of the Timan megablock. Their Rb-Sr ages fall into the interval of 597-587 Ma (2), while the Pb-Pb (Pb evaporation) method yielded zircon ages of 621 ± 3.5 Ma (3). Here�

Thermogravimetric measurement of evaporation: Data analysis based on the Stefan tube

Commercial thermogravimetric analyzers (TGA) can precisely measure the evaporation of liquids from an open pot. Analysis of this data to determine vapour pressure has often been based on the Langmuir equation for evaporation in a vacuum. These methods are flawed, since they cannot account correctly for the effects of ambient air. We formulate an improved model for evaporation in a TGA, based on the Stefan tube. It incorporates these effects explicitly. We demonstrate its validity by determining accurate vapour pressures for pure liquids, without using a reference sample. Calculated values typically agree with literature data to within a few per cent, over a range of vapour pressures from 60Pa to 30kPa. A weakness of thermogravimetric determination of vapour pressure has been that its accuracy depends on the end correction. Our data analysis avoids this problem. Also, the air flow rate and the end effect are shown to act separately on evaporation. Accurate results depend on correctly accounting for both. Finally, a simple heat balance is used to account for the effect of evaporative cooling.

Comparison of actual evaporation from water surface measured by GGI-3000 evaporimeter with values calculated by the Penman equation

Abstract Information about water evaporation is essential for the calculation of water balance. Evaporation, however, is a very complex physical process and it is therefore difficult to quantify. Evaporation measurements from the weather station network of the Czech Hydrometeorological Institute between 1968 and 2011 were performed using the evaporimeter GGI-3000. Evaporation was calculated using modified standard method based on FAO. The aim of the article was to compare the measured values and calculations. It has been found that the evaporation values from water surface calculated using the empirical equation are usually higher than the measured values by on average 0.8 mm, in extreme cases even 6.9 mm. The measured data shows higher variability than the calculated values, which means that correlations between series are not strong, the correlation coefficient being 0.7. Nevertheless the findings can be used for homogenization of series measured by the GGI-3000 evaporimeter.

Use of the transpiration method to study polonium evaporation from liquid lead-bismuth eutectic at high temperature

Abstract Qualitative and quantitative understanding of Po volatilization under different conditions is of key importance for safety assessments of lead-bismuth eutectic (LBE) based nuclear reactors, spallation targets and accelerator driven systems. In this work we explore the possibilities of the transpiration method in combination with simple models to study the equilibrium and kinetics of Po evaporation from highly diluted solutions in lead-bismuth eutectic between 600 and 1000 ℃ in Ar/5% H2 and Ar. On the basis of evaporation experiments at various carrier gas flow rates, we identified the conditions of vapor saturation allowing the determination of equilibrium constants. From the limiting behavior at high flow rates, values for the maximal evaporation rate of Po from LBE were estimated. Measurements of evaporation as a function of time were consistent with the assumption that polonium dissolved in LBE obeys Henry's law. A theoretical analysis furthermore suggested that diffusion of polonium in LBE was not a rate limiting factor for evaporation under vapor saturation conditions. Newly determined values for the Henry constant of Po in LBE between 600 and 1000 ℃ were consistent with previously derived correlations.

In situ measurement shows ocean boundary layer physical processes control catastrophic global warming.

The infrared greenhouse gas heat trap at the top of the atmosphere controls anthropogenic global warming (AGW) heat balance. Processes at the top of the ocean similarly control the 93% of AGW in the oceans. The tropics are a global year-round ocean heat source. Heat is transported in the ocean by sinking brine from tropical evaporation and polar freezing. Buoyant freshwater and ice barriers limit heat loss from the surface layer. The almost completely unstudied ocean surface skin is critically important to understanding global warming and climate change processes. Studies to date have concentrated on atmospheric warming mainly from land-air data. In this paper we present the first hourly meridional 3m and surface observations in the equatorial Pacific from Tahiti to Hawaii for direct measurement of evaporation and ocean boundary layer heat trapping. We relate this to poleward heat and freshwater transport and ocean warming moderation by basal icemelt of floating ice explored in a second paper [1].We show heat sequestration below 3m in the hypersaline (>35.5‰) southern hemisphere (SH) is limited to ~6MJm-2day-1 but evaporation is 7.3mmm-2day--1, at salinity ~36.4‰ and temperature >28ºC. In the northern hemisphere (NH) tropics the corresponding figures are ~12 MJm-2day-1 and ~4.5mmm-2day--1. Equatorial upwelling and the 50m deep Bering Strait limit buoyant surface outflow from the North Pacific.We found pairs of counter-rotating vertical meridional tropical cells (MTCs), ~300-1200km wide, ~100m deep form separate SH and NH systems with little cross-equatorial flux. Counter-rotating Lagrangian wind-driven gyres transport heat and freshwater polewards in seasonally and tidally moderated stratified surface waters. The zonal geostrophic balance is maintained by the Equatorial Undercurrent (EUC) with an eastbound core ~140cms-1 and density ~25.0 at 50-150m.Global warming and polar icemelt has been underestimated from wrong assumptions of the processes in the top 3m of oceans. These are the unverified beliefs that ocean evaporation depends on windspeed and relative humidity that the ocean is well mixed to 10m depths, and by neglect of water density determined by both salinity and temperature. Temperature measurement to ±0.01ºC is required to account for the 3000x greater volumetric heat capacity of seawater to air (3.9x106: 1.3x103Jm-3°C-1). Most SST data are to atmospheric standards (>±0.5°C). Evaporation depends only on temperature (Clausius-Clapeyron). Heat sequestration depends on the buoyant surface layer processes and underlying density gradient. Eleven interconnected counter-rotating Lagrangian wind-driven surface gyres form a global circulation system that carries buoyant surface water masses at speeds much higher than Eulerian geostrophic currents. Polar ice may erode year-round from basal melting from warm subsurface water.This explains contrasting Arctic/Antarctic warming impacts. We suggest many more in situ 3m timeseries especially meridional ones are needed to confirm our findings. In a second paper on centennial daily surface timeseries we show ocean surface warming trend rate post about 1976-1986 is ~0.037ºCyr-1, i.e. >1ºC in 20 years [1]. We suggest global warming research be concentrated on the top of the ocean through multidisciplinary timeseries fieldwork verification, monitoring and modeling. This would best be conducted through a cost-efficient dynamic adaptive scientific management for rapid determination of mitigation and adaptation strategies. Reducing troposphere greenhouse gases can only reduce warming. Mitigation maybe possible through heat energy extraction from geothermal, ocean, tidal and solar sources.

Operational monitoring of daily evapotranspiration by the combination of MODIS NDVI and ground meteorological data: Application and evaluation in Central Italy

Time-varying crop coefficients (Kc) can be obtained from remotely sensed data and combined with daily potential evapotranspiration estimates for the operational prediction of actual evapotranspiration (ETA). This approach, however, presents relevant limitations when applied in mixed, water stressed ecosystems. The current paper addresses these issues by introducing two innovations. First, fractional vegetation cover (FVC) is derived from NDVI and utilized to split evaporating and transpiring surfaces, whose behavior is simulated under fully watered conditions by the use of generalized Kc. Next, the short term effect of water shortage is taken into account by means of downregulating factors which are based on meteorological observations (potential evapotranspiration and rainfall) and act differently for vegetated and not vegetated surfaces. The new method is tested against latent heat of evaporation (LE) measurements taken by the eddy covariance technique in six sites of Central Italy representative of various forest and herbaceous ecosystems. In this experiment the method is driven by 1-km meteorological data obtained from a pan-European archive and by 250m MODIS NDVI imagery. Satisfactory accuracies are obtained in all experimental situations, which encourages the application of the method for the operational monitoring of ETA on regional scale.

Exploring the long-term balance between net precipitation and net groundwater exchange in Florida seepage lakes

The long-term balance between net precipitation and net groundwater exchange that maintains thousands of seepage lakes in Florida’s karst terrain is explored at a representative lake basin and then regionally for the State’s peninsular lake district. The 15-year water budget of Lake Starr includes El Niño Southern Oscillation (ENSO)-related extremes in rainfall, and provides the longest record of Bowen ratio energy-budget (BREB) lake evaporation and lake-groundwater exchanges in the southeastern United States. Negative net precipitation averaging −25 cm/yr at Lake Starr overturns the previously-held conclusion that lakes in this region receive surplus net precipitation. Net groundwater exchange with the lake was positive on average but too small to balance the net precipitation deficit. Groundwater pumping effects and surface-water withdrawals from the lake widened the imbalance. Satellite-based regional estimates of potential evapotranspiration at five large lakes in peninsular Florida compared well with basin-scale evaporation measurements from seven open-water sites that used BREB methods. The regional average lake evaporation estimated for Lake Starr during 1996–2011 was within 5% of its measured average, and regional net precipitation agreed within 10%. Regional net precipitation to lakes was negative throughout central peninsular Florida and the net precipitation deficit increased by about 20 cm from north to south. Results indicate that seepage lakes farther south on the peninsula receive greater net groundwater inflow than northern lakes and imply that northern lakes are in comparatively leakier hydrogeologic settings. Findings reveal the peninsular lake district to be more vulnerable than was previously realized to drier climate, surface-water withdrawals from lakes, and groundwater pumping effects.

Lagrangian measurements of the fast evaporation of falling diethyl ether droplets using in-line digital holography and a high-speed camera

The evaporation of falling diethyl ether droplets is measured by following droplets along their trajectories. Measurements are performed at ambient temperature and pressure by using in-line digital holography. The holograms of droplets are recorded with a single high-speed camera and reconstructed with an “inverse problems” approach algorithm previously tested (Chareyron et al. New J Phys 14:43039, 2012). Once evaporation starts, the interfaces of the droplets are surrounded by air/vapor mixtures with refractive index gradients that modify the holograms. The central part of the droplets holograms is unusually bright compared to what is expected and observed for non-evaporating droplets. The reconstruction process is accordingly adapted to measure the droplets diameter along their trajectory. The diethyl ether being volatile, the droplets are found to evaporate in a very short time: of the order of 70 ms for a 50–60 μm diameter at an ambient temperature of 25 °C. After this time, the diethyl ether has fully evaporated and droplets diameter reaches a plateau. The remaining droplets are then only composed of water, originating from the cooling and condensation of the humid air at the droplet surface. This assertion is supported by two pieces of evidence: (i) by estimating the evolution of droplets refractive index from light scattering measurements at rainbow angle and (ii) by comparing the evaporation rate and droplets velocities obtained by digital holography with those calculated with a simple model of evaporation/condensation. The overall results show that the in-line digital holography with “inverse problems” approach is an accurate technique for studying fast evaporation from a Lagrangian point of view.

The hysteretic evapotranspiration—Vapor pressure deficit relation

AbstractDiurnal hysteresis between evapotranspiration (ET) and vapor pressure deficit (VPD) was reported in many ecosystems, but justification for its onset and magnitude remains incomplete with biotic and abiotic factors invoked as possible explanations. To place these explanations within a holistic framework, the occurrence of hysteresis was theoretically assessed along a hierarchy of model systems where both abiotic and biotic components are sequentially added. Lysimeter evaporation (E) measurements and model calculations using the Penman equation were used to investigate the effect of the time lag between net radiation and VPD on the hysteresis in the absence of any biotic effects. Modulations from biotic effects on the ET‐VPD hysteresis were then added using soil‐plant‐atmosphere models of different complexities applied to a grassland ecosystem. The results suggest that the hysteresis magnitude depends on the radiation‐VPD lag, while the plant and soil water potentials are both key factors modulating the hysteretic ET‐VPD relation as soil moisture declines. In particular, larger hysteresis magnitude is achieved at less negative leaf water potential, root water potential, and soil water potential. While plant hydraulic capacitance affects the leaf water potential‐ET relation, it has negligible effects on the ET‐VPD hysteresis. Therefore, the genesis and magnitude of the ET‐VPD hysteresis are controlled directly by both abiotic factors such as soil water availability, biotic factors (leaf and root water potentials, which in turn depend on soil moisture), and the time lag between radiation and VPD.

Evaporation from Water Surfaces in Arid and Semi-Arid Areas in Algeria

The evaporation from open water remains a difficult process to measure or estimate. The major source of difficulty is the fact that the required meteorological parameters are rarely measured over the water. In this study, we calculate the evaporation rate from the pan using the energy budget method which is widely considered to be the most accurate method of estimating evaporation and A CFD-based methodology to estimate monthly evaporation for the two dams. The evaporation rates calculated with the energy budget and the application of CFD were in good agreement with monthly evaporation measurements in dams located in areas of different climates in Algeria.

Up-scaling short-term process-level understanding to longer timescales using a covariance-based approach

Abstract. General experience in hydrologic modelling suggests that the parameterisation of a model changes over different time and space scales. As a result, hydrologists often re-parameterise their models whenever different temporal or spatial resolutions are required. Here, we investigate theoretical aspects of this issue in a search for the cause(s) of the need for re-parameterisations. Based on Taylor series expansion, we present a mathematical approach for temporal up-scaling that involves covariance-based corrections. We apply the theory using a unique database of half-hourly pan evaporation measurements (comprising 237 days) and examine how the model parameters change when integrating from half-hour to daily and then monthly integration periods. We show that the model parameters change over different integration periods because of changes in the covariance between the model variables. In our model system, we find that the covariance-based correction is highly variable from day to day but settles down to a reasonably constant value over periods longer than about 15 days. The 15 days timescale is likely to be specific to our model system, nonetheless the underlying principle that there is a characteristic timescale for the covariance-based scaling correction of a particular hydrologic process might be general. If that proved true it would open up the possibility of systematically searching for characteristic integration periods for the key covariance-based scaling terms in other key hydrologic processes. That would in turn enable the development of more generalised hydrologic closure scheme(s).

Quantification of surface energy fluxes from a small water body using scintillometry and eddy covariance

[1] Accurate quantification of evaporation from small water storages is essential for water management and planning, particularly in water-scarce regions. In order to ascertain suitable methods for direct measurement of evaporation from small water bodies, this study presents a comparison of eddy covariance and scintillometry measurements from a reservoir in southeast Queensland, Australia. The work presented expands on a short study presented by McJannet et al. (2011) to include comparisons of eddy covariance measurements and scintillometer-derived predictions of surface energy fluxes under a wide range of seasonal weather conditions. In this study, analysis was undertaken to ascertain whether important theoretical assumptions required for both techniques are valid in the complex environment of a small reservoir. Statistical comparison, energy balance closure, and the relationship between evaporation measurements and key environmental controls were used to compare the results of the two techniques. Reasonable agreement was shown between the sensible heat flux measurements from eddy covariance and scintillometry, while scintillometer-derived estimates of latent heat flux were approximately 21% greater than eddy covariance measurements. We suggest possible reasons for this difference and provide recommendations for further research for improving measurements of surface energy fluxes over small water bodies using eddy covariance and scintillometry.

Coated interconnects development for high temperature water vapour electrolysis: Study in anode atmosphere

High temperature water vapour electrolysis (HTE) is an efficient technology for hydrogen production. In this context, a commercial stainless steel, K41X (AISI 441), was chosen as interconnect. In a previous paper, the high temperature corrosion and the electrical conductivity were evaluated in both anode (O2–H2O) and cathode (H2–H2O) atmosphere at 800 °C. In O2–H2O atmosphere, the formation of a thin chromia protective layer was observed. Nevertheless, the ASR parameter measured was higher than the maximum accepted value. These results, in addition with chromium evaporation measurements, proved that the K41X alloy is not suitable for HTE interconnect application. In this study, two perovskite-type oxides La0.8Sr0.2MnO3−δ and LaNi0.6Fe0.4O3−δ were tested as coatings in O2–H2O atmosphere at 800 °C. Screen-printing and physical vapour deposition were used as coating processes. The high temperature corrosion resistance and the electrical conductivity were improved, especially with the LaNi0.6Fe0.4O3−δ coating. Cr specie volatility was also reduced.

River evaporation and corresponding heat fluxes in forested catchments

AbstractRiver water temperature is a very important variable in ecological studies, especially for the management of fisheries and aquatic resources. Temperature can impact on fish distribution, growth, mortality and community dynamics. River evaporation has been identified as an important heat loss and a key process in the thermal regime of rivers. However, its quantification remains a challenge, mainly because of the difficulty of making direct measurements. The objectives of this study were to characterize the evaporative heat flux at different scales (brook vs river) and to improve the estimation of the evaporative heat flux in a stream temperature model at the hourly timescale. Using a mass balance approach with floating minipans, we measured river evaporation at an hourly timescale in a medium‐sized river (Little Southwest Miramichi) and a small brook (Catamaran Brook) in New Brunswick, Canada. With these direct measurements of evaporation, we developed mass transfer equations to estimate hourly evaporation rates from microclimate conditions measured 2 m above the stream. During the summer 2012, river evaporation was more important for the medium‐sized river with a mean daily evaporation rate of 3.0 mm day−1 in the Little Southwest Miramichi River compared with that of 1.0 mm day−1 in Catamaran Brook. Evaporation was the main heat loss mechanism in the two studied streams and was responsible for 42% of heat losses in the Little Southwest Miramichi River and 34% of heat losses in Catamaran Brook during the summer. Copyright © 2013 John Wiley & Sons, Ltd.