Forced Evaporation Research Articles

Landfill leachate treatment by evaporation in open and closed systems under low temperature in southern Brazil

The leachate produced in landfills represents one of the main environmental risks. Among the main emerging techniques of leachate treatment is evaporation. The present study aimed to implement and monitor the performance of natural and forced evaporation technology in open and closed systems. The open pilot experiment system consisted of storage tanks, sprinklers and an evaporative panel, obtaining an average evaporation rate in the system of over 100 L.day−1. For the closed pilot system, different temperatures were combined with different air speeds, simulated by a fan. The results obtained during this operation ranged from 7.7 to 127.2 L.day−1 for the various climatic conditions simulated. In both experiments, wind speed proved to be the most significant climatic characteristic, followed by temperature. With regard to the dispersion of microorganisms in the air, both pilots showed a downward trend in colony-forming units (CFUs) as the distance increased. The volatile organic compound (VOCs) most likely to be present in the atmosphere surrounding the experiments were Dimethyl-Diazene, Tetramethyl-Silane, 2-Nitro-Propane, and 3-Methyl-Butanenitrile. The performance of leachate evaporation, which can be applied in various climatic conditions, leads to the conclusion that these techniques are a viable alternative to conventional landfill leachate treatment methods.

Realization of a quantum degenerate mixture of highly magnetic and nonmagnetic atoms

We report on the experimental realization of a bosonic quantum degenerate mixture of highly-magnetic 168Er and nonmagnetic 174Yb. Quantum degeneracy is reached by forced evaporation in an all-optical trap. Formation of the two Bose-Einstein condensates is confirmed by analysis of the cloud shape and the observed inversions of the aspect ratios. The results open a path for possible new experiments on magnetic and nonmagnetic impurity physics as well as on the quantum chaotic behavior of Feshbach resonances and their dependencies on minor variations of the reduced masses.

Fast, simple, all-optical production of sodium spinor condensates

We present an experiment for quickly producing Bose–Einstein condensates (BECs) of 23Na atoms in a simple crossed dipole trap. The atoms were collected in a magneto-optical trap from a zero-crossing Zeeman slower. The atoms are then transferred to a tightly focused crossed optical dipole trap, and a pure F = 1 BEC of ∼1.1 × 105 sodium atoms was created by a fast forced evaporation. Our system reliably generates the condensate at a rate exceeding 105 atoms every ∼8 s. We also compare the lifetimes of the mixed F = 1 condensate and the spin components (m F = 0, m F = +1).

Hydraulic hysteresis of natural pyroclastic soils in partially saturated conditions: experimental investigation and modelling

In many geotechnical applications, especially in the study of weather-induced landslides, a reliable soil hydraulic characterization in unsaturated conditions is required. Currently, the experimental techniques that neglect the hydraulic hysteresis represent the greatest limitation to landslide forecasting. In this paper, a procedure to obtain an unsaturated soil hydraulic characterization on natural pyroclastic samples is proposed and verified. The approach enables the evaluation of the soil hydraulic properties along the main drying path and wetting/drying cycles to fully quantify the effects of the hydraulic hysteresis. Pyroclastic soil samples collected at a test site at Mount Faito in the Campania region (southern Italy) were tested. The experimental investigation consisted of a sequence of testing phases: a constant-head hydraulic conductivity test, a forced evaporation test followed by several wetting–drying cycles, and a drying test in a pressure plate apparatus. The hysteretic model proposed by Parker and Lenhard (1987) was adopted to fit the data, while inverse modelling of the forced evaporation tests allowed to derive the model parameters. Therefore, the main drying and wetting branches and the soil response to drying and wetting cycles from any reversal point were reproduced with the model, which suitably described the hysteretic behaviour of the pyroclastic soil under all conditions and along all paths.

Droplet Entrainment Analysis in a Flash Evaporator with an Image‐Based Measurement Technique

AbstractLocal droplet sizes and volumes of entrained liquid are captured with an image‐based measurement technique for comparison with a conventional, integral method for entrainment analysis. Experiments in a forced circulation flash evaporation were performed for different operating conditions and with two different chemical systems. Droplet size and frequency rise with an increase in thermal energy input. The local readings confirm the trends found by the integral measurement method. The modification of the image‐based probe enables the detection of small (≈ 10 µm) and at the same time fast droplets under challenging operating conditions, such as vacuum and superheated feed similar to industrial process conditions.

Advanced Energy-Saving Technology of Granular Nitrate-Containing NPK-Fertilizers

There was developed the technology of granular balanced nitrate-containing NPK-fertilizers 16-16-16 and 17-17-17. Key features of the proposed technology are: - Joint ammoniation of a mixture of nitric and phosphoric acids to a molar ratio of NH3:H3PO4 1.4÷1.5 and complete-ammoniation in Ammoniatior-Granulator drum to 1.65÷1.8. - Due to more efficient use of acid neutralization heat, the fluent slurry is obtained with low moisture content required for granulation. Ammoniation of a mixture of nitric and phosphoric acids at higher molar ratio makes it possible to exclude the possibility of acidification of ammonium nitrate, which causes the process of self-accelerating decomposition. The production of fertilizer grades with an increased molar ratio in the product have the following advantages: - higher degree of WPA neutralization to a molar ratio of NH3:H3PO4 of 1.65÷1.8 mol / mol allows to reduce the consumption of nitric acid and to exclude the stage of forced evaporation of nitrate slurry and the stage of ammonium nitrate melt preparation; - the cost of NPK-fertilizers with a lower content of ammonium nitrate is lower due to partial substitution of the nitrate nitrogen for ammonia nitrogen. - improvement of physical and chemical properties of the final product due to reduction of nitrate nitrogen content, - thermal stability of the obtained nitrate-containing NPK-fertilizers with an increased molar ratio in the product 1.65÷1.8; - flexibility to obtain a broad range of NPK-fertilizer grades.

Using Solar Energy for Autonomous Water Supply to Communities

Global water consumption grow steadily. In regions with a shortage of fresh water, its production is accompanied by a significant expenditure of energy, as a rule, it is a burning of hydrocarbon fuels. This factor has a negative impact on the environment. The aim of this work is to develop an energy-efficient “green” technology for the desalination of seawater and the production of fresh water from contaminated sources, through its forced evaporation with subsequent condensation of moisture. The process of obtaining fresh water is due to pre-saturated air in a closed thermodynamic cycle. The paper presents the thermal balance of modular installations. To increase the insolation power per unit area, it is possible to use various centers of solar energy. Experimental studies and a comparison of the performance of two variants of desalination plants in water with each other and with theoretically possible productivity were carried out. The productivity of the technologies is sufficient for the autonomous supply of drinking water to individual settlements and for the cultivation of plant foods by the hydroponic method.

Efficacy of forced condensation and forced evaporation with thermal energy storage material on square pyramid solar still

Authors have attempted to investigate the impact of thermal storage material, forced condensation and forced evaporation on the performance of square pyramid solar still. The experimentation was conducted in three sets. First set was carried out with and without thermal storage (black granite) and variable water depth (20 mm and 30 mm). The daily yield of 1430.40 ml/m2 (13.96% higher) was obtained for the still with thermal storage at water depth of 30 mm. The second set was conducted for studying the impact of forced condensation and forced evaporation with thermal storage on the performance of still at 30 mm water depth. Compared to the still with forced condensation, increment of 33.24% was observed in daily yield for the still with forced evaporation. The effect of forced evaporation and thermal storage on yield and efficiency was compared with the still without augmentation at 30 mm water depth in third set. The daily yield of 2253.6 ml/m2 (61.48% higher) and the efficiency of 27.04% (61.53% higher) were achieved for the still with forced evaporation and thermal storage. The still with forced evaporation and thermal storage at water depth of 30 mm has proved most productive, efficient and economic.

Water evaporation at wet-cooled nuclear power plants on river banks: Application to the French Rhône river

Nuclear power plants (NPP) installed on a river bank use once-through or recirculating wet cooling systems. While the quantitative assessment of mainly local evaporation of river water by a recirculating cooling system (RC) does not involve any major difficulty, the same cannot be said for the once-through cooling system (OTC) for which evaporation (called forced evaporation) occurs in the downstream aquatic environment. Our study applies an energy-balance temperature model to the Rhône River downstream from Lake Geneva. Our results show the approximate figure of 1.5 m3/MWh of forced evaporation per electricity produced (put forward in 2002 by EPRI and widely used in the literature) is debatable for setting a freshwater balance in a watershed because it does not consider the saltiness of the river downstream. The retention time of water bodies in the downstream freshwater stretch, the cross-section shape and regional weather characteristics appear to be key factors to take into account. In particular, for the three NPP with OTC systems installed along the French Rhône, we find an average forced evaporation between 0.3 and 0.7 m3/MWh of net electricity generated in the freshwater river stretch through to Arles between 1994 and 2015. These values are between three to eight times lower than those obtained for the evaporation generated by the plants with RC system installed along the river stretch.

Pressure loss and performance assessment of horizontal spiral coil inserted pipes during forced convective evaporation of R-600a

The impacts of spiral coil inserts on the pressure loss of environment-friendly refrigerant R-600a are experimentally evaluated during forced convective evaporation within horizontal copper pipes. Then, by considering the current pressure drop and previous heat transfer results and calculating the performance factor, the overall effectiveness of the inserts is determined. Experiments are carried out for smooth and rough tubes. Five spiral coils with various coil pitches and wire diameters are utilized. Also, vapor qualities between 0.08 and 0.7 and mass fluxes between 109.2 and 505 kg m−2 s−1 are considered for tests. Generally, it is observed that inserts augment the pressure loss in the range of 90–958% over the smooth pipe. However, as the wire diameter decreases and the coil pitch increases, less pressure losses are imposed to the system. Depending on the operational conditions and inserts type, the performance factor was obtained between 0.13 and 1.40. The coiled wire “CW5” with the wire diameter of 1 mm and coil pitch of 30 mm performed superior compared to the other inserts by maximum performance factor of 1.4. Finally, by using the current data a new correlation is proposed in order to predict the evaporative pressure loss of R-600a within spiral coil inserted pipes.

A pore-level direct numerical investigation of water evaporation characteristics under air and hydrogen in the gas diffusion layers of polymer electrolyte fuel cells

During the operation of polymer electrolyte fuel cells (PEFC) liquid water clusters generated due to electrochemical reactions in the gas diffusion layers (GDL) create a resistance against gas transport towards the catalyst layers (CL), and hence must be efficiently removed to maintain the cell performance, a process often realized by means of forced evaporation. Water accumulation is of interest not only for the cathode GDL but also for the anode GDL, particularly under thermoneutral cell operation whereby liquid water can be added to either anode or cathode channel flows. Although many works studied water evaporation in air and especially at moderate temperatures, less effort has been devoted in investigating evaporation at elevated temperatures and at the anode side, where hydrogen flows in the gas channels. In this work, direct numerical simulation is used to characterize evaporation at pore level for both anode and cathode sides and at different temperatures (up to 80 °C), for which experimental data are rare and micro-scale transport is often difficult to assess in the laboratory. Realistic water distribution and porous GDL geometry, acquired from X-ray tomography, have been used while regularized distributions of liquid water are further considered in order to investigate evaporation at various saturation levels. Key results indicate that (a) the water evaporation rate in hydrogen flows can be up to 4 times larger than the corresponding one in air flows at the same gas stream velocity and temperature, (b) the predicted vertical evaporation-induced velocities under hydrogen are an order of magnitude bigger than the corresponding ones under air and they can grow large enough at elevated temperatures to potentially hamper hydrogen transport towards the CLs.

A versatile apparatus for fermionic lithium quantum gases based on an interference-filter laser system.

We report on the design and construction of a versatile setup for experiments with ultracold lithium (Li) gases. We discuss our methods to prepare an atomic beam and laser cool it in a Zeeman slower and a subsequent magneto-optical trap, which rely on established methods. We focus on our laser system based on a stable interference-filter-stabilized, linear-extended-cavity diode laser, so far unreported for lithium wavelengths. Moreover, we describe our optical setup to combine various laser frequencies for cooling, manipulation, and detection of Li atoms. We characterize the performance of our system preparing degenerate samples of Li atoms via forced evaporation in a hybrid crossed-beam optical-dipole trap plus confining magnetic trap. Our apparatus allows one to produce quantum gases of N ≈ 105…106 fermionic lithium-6 atoms at nanokelvin temperatures in cycle times below 10 s. Our optical system is particularly suited to study the dynamics of fermionic superfluids in engineered optical potentials.

Boiling heat transfer and flow characteristic of R32 inside a horizontal small-diameter microfin tube

This study experimentally investigated the flow boiling heat transfer and pressure drop characteristics of R32 inside a horizontal small-diameter microfin tube with an equivalent diameter of 3.48 mm. The boiling heat transfer coefficient and pressure drop were measured in a mass velocity range of 50–400 kgm−2 s−1, heat flux range of 5–20 kWm−2, and saturation temperature of 15 °C. The flow pattern at the outlet of the test microfin tube was observed and classified as wavy-slug flow and annular flow regime. The effects of quality, mass velocity, heat flux, and flow pattern on the flow boiling characteristics were clarified. The heat transfer mechanism was characterized by forced convection, nucleate boiling, and evaporation heat transfer through the thin liquid film inside the grooves. No difference in the frictional pressure drop on adiabatic and boiling flows was observed. The measured heat transfer and frictional pressure drop were compared with those in previous correlations.

Simulating latrine conditions to assess perfume performance against malodour.

To evaluate perfume performance in toilets, we built model toilets in which critical factors such as background malodour, climate, and airflow were controlled. The models were equipped with an odour generator that injected hydrogen sulfide, methyl mercaptan, butyric acid, para‐cresol, and indole, allowing us to accurately and reliably reconstitute toilet malodour headspace. The malodorant concentrations matched the quantitative headspace analysis performed in African and Indian toilets. The toilet malodour headspace performance was validated by chemical and sensory analysis. Olfactory stimuli were presented to participants in different simulated climates to assess the effect of climate on the perception of odours. The sensory data show that increasing temperature and humidity decreased the intensity ratings of odours without altering their quality. Perfume can be delivered in these toilets by forced evaporation to control the headspace concentration, or by delivery systems such as cellulosic pads, liquids, and powders. Our experimental set‐up allowed us to establish dose–response curves to assess the performance of a perfume in reducing toilet malodour and increasing perceived pleasantness.

An empirical study on evaporation heat transfer characteristics and flow pattern visualization in tubes with coiled wire inserts

In the present work, heat transfer and flow pattern visualization during forced convection evaporation of hydrocarbon R-600a (Isobutane) inside a horizontal tube with coiled wire inserts has been experimentally studied. The system consists of a pump, two preheaters, the test section, two condensers, flow meter and bypass. The test evaporator was an electrically heated copper tube of 1000mm length, 8.1mm inside diameter and a wall thickness of 0.71mm. Coiled wires with three different wire diameters of 0.5, 1.0 and 1.5mm and three different coil pitches of 10, 20 and 30mm were made and used in full length of test evaporator. The test runs were carried out at refrigerant mass fluxes from 109.2 to 505kg/m2s and heat fluxes between 18.6 and 26.1kW/m2. The use of coiled wires was found to increase the flow boiling heat transfer coefficients up to maximum value of 124% above the plain tube values with wire coiled having a twist ratio (PDin) of 1.243 and a thickness ratio (eDin) of 0.183. Four different flow patterns were observed and classified as bubbly, stratified, intermittent and annular flow. This study reveals the developments of the flow patterns. Also it was observed that the presence of coiled wire inserts induces disturbance into gas and liquid flows and so that the shape and motion of bubbles and slug are different from those observed in a plain tube. The correlation suggested by Shah [20] gave the best prediction to the flow boiling heat transfer coefficient in the plain tube within the studied ranges.

Thermodynamic modeling of phases equilibrium in aqueous systems to recover potassium chloride from natural brines

Chemical fertilizers, such as potassium chloride, ammonium nitrate and other chemical products like sodium hydroxide and soda ash are produced from electrolyte solutions or brines with a high content of soluble salts. Some of these products are manufactured by fractional crystallization, when several salts are separated as solid phases with high purity (>90%). Due to the large global demand for potassium fertilizers, a good knowledge about the compositions of salts and brines is helpful to design an effective process. A thermodynamic model based on Pitzer and Harvie's model was used to predict the composition of crystallized salts after water removal by forced evaporation and cooling from multicomponent solutions or brines. Initially, the salts’ solubilities in binary systems (NaCl–H2O, KCl–H2O and MgCl2–H2O) and ternary system (KCl–MgCl2–H2O) were calculated at 20°C and compared with literature data. Next, the model was compared to our experimental data on the quinary system NaCl–KCl–MgCl2–CaCl2–H2O system at 20°C. The Pitzer and Harvie's model represented well both the binary and ternary systems. Besides, for the quinary system the fit was good for brine densities up to 1350kg/m3. The models were used to estimate the chemical composition of the solutions and salts produced by fractional crystallization and in association with material balance to respond to issues related to the production rates in a solar pond containing several salts dissolved, for instance, NaCl, KCl, MgCl2 and CaCl2.

Experimental study on thermo-hydrodynamic behaviors in miniaturized two-phase thermosyphons

In this paper, the thermo-hydrodynamic behaviors in miniaturized two-phase thermosyphons are experimentally investigated by a visualization system. The effects of heat load and channel dimension on the thermo-hydrodynamic behaviors are examined and further quantitatively recognized by a state diagram depending on the Weber number and Bond number. In addition, the vapor–liquid two-phase flow, heat transfer regimes and thermal performances are analyzed and discussed. The results indicate that, differing from the conventional two-phase thermosyphon, the state of working fluid in a miniaturized two-phase thermosyphon is no longer only in a fashion of pool and annular-flow states, but also in a fashion of oscillation state. The oscillation state is the characteristic two-phase flow regime of a miniaturized two-phase thermosyphon and possesses the feature of random formation and oscillatory motion of liquid plug in minichannels. The pool state occurs at small Weber number, the annular-flow state is observed at large Weber number, and the oscillation state takes place at medium Weber number when Bond number is approximately smaller than 0.7. The thermal performance of oscillation state is better than that of pool state but is less powerful than that of annular-flow state. The heat transfer regimes are the film evaporation and condensation combined with thermal conduction in the pool state, the forced evaporation and condensation in the oscillation state, and the film evaporation and condensation in the annular-flow state, respectively.

Hydrophilic Magnetofluorescent Nanobowls: Rapid Magnetic Response and Efficient Photoluminescence.

Multifunctional integration based on a single nanostructure is emerging as a promising paradigm to future functional materials. In this paper, novel magnetofluorescence nanobowls built with ferroferric mandrel and quantum dots exoderm is reported. Magnetic mandrels are stacked into nanobowls though hydrophobic primary Fe3O4 nanocrystals dragged into anion polyelectrolyte aqueous solution via forced solvent evaporation. Bright luminescence core/shell/shell CdSe/CdS/ZnS quantum dots (QDs) are modified with cationic hyperbranched polyethylenimine (PEI). Through electrostatic interactions, positively charged PEI-coated QDs are anchored on the surface of magnetic mandrel. Under this method, the luminescence of QDs is not quenched by magnetic partners in the resultant magnetoflurescence nanobowls. Such magnetoflurescence nanobowls exhibit high saturation magnetization, superparamagnetic characteristics at room temperature, superior water dispersibility, and excellent photoluminescence properties. The newly developed magnetoflurescence nanobowls open a new dimension in efforts toward multimodal imaging probes combining strong magnetization and efficient fluorescence in tandem for biosensors and clinical diagnostic imaging.

Inverstigation on loading of the Dimple optical trap based on a magnetically levitated large-volume crossed optical dipole trap

Optical trapping techniques and the ability to tune the atomic interactions both have made the unprecedented progress in the quantum gas research field. The major advantage of the optical trap is that the atoms are likely to be trapped at various sub-levels of the electronic ground state and the interaction strength can be controlled by Feshbach resonance. Optical trapping methods in combination with magnetic tuning of the scattering properties directly lead to the experimental achievements of Bose-Einstein condensation (BEC) of Cesium, which at first failed by using magnetic trapping approaches due to the large inelastic collision rate. The rapid loss of cesium atoms due to the inelastic two-body collisions greatly suppresses the efficient evaporative cooling to obtain a condensate. For optical production of cesium atomic BEC, it is necessary to prepare a large number of Cs atoms at specified state in an optical trap for condensation, especially for an efficient forced evaporation cooling. In this paper, we demonstrate our research on enhancing the loading rate of the atoms by using a dimple trap combined with a large-volume optical dipole trap (reservoir trap). In our work, the cold cesium atoms are prepared by a three-dimensional degenerated Raman sideband cooling, and then loaded into a large-volume crossed dipole trap by using the magnetic levitation technique. Effective load of the dimple optical trap is realized by superposing the small-volume dimple trap on the center of the largevolume optical trap. The theoretical analyses are performed for the magnetically levitated large-volume crossed dipole trap in variable magnetic field gradients and uniform bias fields. Optimal experimental values are acquired accordingly. The combined potential curve of the dimple trap, which is superimposed on the magnetically levitated large-volume dipole trap, is also given. The loading of precooled atoms from Raman sideband cooling into the magnetically levitated large-volume optical trap is measured in variable magnetic field gradients and uniform bias fields. Different loading results of the dimple trap are investigated, including direct loading after Raman sideband cooling, the large-volume optical trap and the magnetically levitated large-volume dipole trap without anti-trapping potential. Comparatively, the atomic number density is enhanced by a factor of ~15 by loading the atomic sample from the magnetically levitated large-volume dipole trap into the dimple optical trap. The experimental results lay a sound basis for the further cooling and densifying the atomic cloud through the evaporating cooling stage. This method can be used to obtain more cold atoms or a large number of Bose-Einstein condensation atoms for atomic species with large atom mass.

Multipartite model of evaporative cooling in optical dipole traps

We propose and study a model of forced evaporation of atomic clouds in crossed-beam optical dipole traps that explicitly includes the growth of a population in the ``wings'' of the trap and its subsequent impact on dimple temperature and density. It has long been surmised that a large wing population is an impediment to the efficient production of Bose-Einstein condensates in crossed-beam traps. Understanding the effect of the wings is particularly important for $\ensuremath{\lambda}=1.06\phantom{\rule{0.16em}{0ex}}\ensuremath{\mu}\mathrm{m}$ traps, for which a large ratio of Rayleigh range to beam waist results in wings that are large in volume and extend far from the dimple. Key ingredients to our model's realism are (1) our explicit treatment of the nonthermal, time-dependent energy distribution of wing atoms in the full anharmonic potential and (2) our accurate estimations of transition rates among dimple, wing, and free-atom populations, obtained with Monte Carlo simulations of atomic trajectories. We apply our model to trap configurations in which neither, one, or both of the wing potentials are made unbound by applying a ``tipping'' gradient. We find that forced evaporation in a trap with two bound wing potentials produces a large wing population which can collisionally heat the dimple so strongly as to preclude reaching quantum degeneracy. Evaporation in a trap with one unbound wing, such as that made by crossing one vertical beam and one horizontal beam, also leads to a persistent wing population which dramatically degrades the evaporation process. However, a trap with both wings tilted so as to be just unbound enjoys a nearly complete recovery of efficient evaporation. By introducing to our physical model an ad hoc, tunable escape channel for wing atoms, we study the effect of partially filled wings, finding that a wing population caused by single-beam potentials can drastically slow down evaporative cooling and increase the sensitivity to the choice of $\ensuremath{\eta}$.