Papers by Keyword: Evaporation Rate

Abstract: Solar desalination is a process to reduce the salt content in seawater by utilizing solar heat. In recent years, the interfacial heating method has been proposed as an alternative to evaporation by creating localized heat on the surface of the liquid. This study investigated charcoal briquettes as a solar absorber material to accelerate the evaporation rate. The experiment was carried out on four basins of single slope type using charcoal briquettes for 8 hours in the sun with variations in the distance between the cover glass and the absorber, namely 3 cm, 4 cm and 5 cm. Charcoal-free basins were also tested for comparison. Temperature is measured at several points in the basin to identify factors affecting evaporation. The results showed that the structure of charcoal briquettes can concentrate the heat required for phase change. The temperature and humidity in each basin also have a similar changing trend where solar radiation strongly influences temperature. Using charcoal can also increase the basin's convection and evaporation heat transfer rates. The maximum desalination efficiency is obtained in basin 2 with a variation of 4 cm cover glass spacing of 31.45%, followed by a variation of 5 cm cover glass distance in basin 3 of 29.92 %, and the variation of 3 cm glass spacing in basin 1 was 26.98%. Whereas in basin 4, with the variation without charcoal, an efficiency of 38.28% was obtained. Desalination efficiency is influenced by several factors: sun intensity, distillate productivity, latent heat of evaporation, and capillary action.

Abstract: Traditional impermeable pavements such as asphalt have dark surfaces and high thermal inertia. During hot weather, they tend to absorb and store solar radiation, which promotes the development of urban heat islands (UHI). Furthermore, permeable pavements are effective in mitigating the urban heat island effect via evaporative cooling. There are many studies in the literature on the hydraulic and mechanical characteristics of permeable pavements, but a few studies focus on the impact of evaporative cooling of these pavements. In this study, 3 types of permeable pavements based on pozzolan, recycled rubber and polyurethane resin were studied during 3 hot days. The objective was to quantify the cooling effect in these innovative permeable pavements compared to a traditional impermeable asphalt pavement. The results of this experiment show that the cooling effect in the new types of draining pavements can last up to two days in the weather conditions of this experiment compared to the traditional asphalt pavement. The evaporation rate and surface temperature of permeable pavements vary in opposite directions. In addition, evaporation in pervious pavements is controlled by the availability of water near the surface. This study is a preliminary step in the design of pavements that contribute to the valorization of rubber waste, to the stormwater management and to the reduction of the effects of urban heat islands during heat waves.

Abstract: Evaporation and boiling from porous media has drawn a broad attention in many applications ranging from industrial, environmental to engineering and technologies. However, prediction of evaporation rates from porous media remains a challenge due to complex interactions between ambient conditions and the porous media properties such as complex geometry, material of the matrices composing porous medium, many length scales, surface phenomena, and effective transport coefficients. In this study, the evaporation rates of distilled water from porous media of different matrices were studied experimentally. Porous media were made up from spherical brass balls of different diameters of 2 mm, 3 mm, 4 mm and 5 mm. The temperature profiles across porous media, air temperature, humidity, and amount of water evaporated were measured in experiments. The effects of the porosity, the thickness of a porous layer, and particle size on the evaporation from porous media were investigated. Different materials of the porous matrices have allowed bringing to light the influence of the material properties. The experimental data show that the rate of evaporation of distilled water with brass balls is higher than that of only distilled water without a porous medium embedded into the water layer and does not change significantly after a steady state condition is achieved.

Abstract: The influence of natural evaporation factors (the irradiation intensity, speed of the wind, temperature of the brine, temperature and relative humidity of the air) on the desalinated seawater evaporation rate was measured experimentally. A natural evaporation model was built by correlating the experimental data using the artificial neural network. This model was well correlated with the influence of natural evaporation factors, and it showed a good agreement of the results and evaporation theory.

Abstract: The paper is aimed to provide key input for an analysis forming part of industrial process risk assessment and management in a selected enterprise. The analysis is a feature of the Complex model for industrial process risk assessment and management developed in the APVV 0043-10 project. As part of the evaluation of model application, a risk assessment is undertaken in selected enterprises. This risk assessment also involves modelling of a hazardous substance (ammonia water) spillage. To be able to predict the amount of ammonia released and its distribution in time, the evaporation rate must be known. This paper describes laboratory-scale experimental determination of the evaporation rate of ammonia from ammonia water provided by the enterprise for which the risk assessment is being undertaken. The results of the experiment show the dependence of the evaporation rate on the ambient temperature and solution concentration and may be applied directly in a toxic cloud movement model.

Abstract: Air-entraining agent improved the concrete structural viscosity under high-frequency vibration was the reason for this characteristics. For the phenomenon that road concrete early cracking, evaporation rate and early cracking testing was done to compare the different between three curing agents by the influence to moisture loss and crack formation. Studies have shown that: curing agent not only played a role that moisturizer, but also shortened the time of its moisture loss. Then, the quantity length and width of concrete cracks were significantly inhibited because of increasing the amount of curing agent.

Abstract: In Aluminum/Water Reaction Motor chamber, water injection angle plays an important role on mixture of aluminum particle fuel and water droplets and can affect motor performance further. On the basis of FLUENT software and taking phase transition and reaction between water droplets and aluminum particles into account, numerically simulated cases of different water injection angles by Particle Stochastic Trajectory Model. Computed total evaporation rate of water droplets, reaction rate of aluminum particles and specific impulse for the motor. Furthermore judged injection angle effect from these parameters. By comparison and analysis, it is found that hybrid injection case could get best multi-phase mixture effect and specific impulse performance for the motor. Namely axial injection angle with 45°in the main chamber and tangential injection angle with 60°in the afterburning chamber is the best case. The conclusion could provide a new idea for motor working process design.

Abstract: Water-reducer is one of the dispensable components in modern concrete, can improve the workability and mechanical performance of concrete, and also has an important influence on the plastic cracking resistance of concrete. In this paper, the flat cracking test was used to evaluate the effect of water reducer on the plastic cracking resistance of concrete, meanwhile, capillary pressure; plastic settlement and evaporation rate were also tested. The results showed that water-reducer could improve the plastic cracking resistance of concrete significantly, and the effectiveness of polycarboxylate water reducer were o better than that of wood calcium and naphthalene water reducer.

Abstract: The evaporation rate of histidine-water system was measured and the influence of pressure, temperature, His concentration, pH value of solution and the existence of NH4Cl salt was investigated. The results showed that operating pressure and temperature have significant influence on evaporation rate. Increasing vacuum and temperature could increase the rate. In contrast, the rate value was insensitive to the change of concentration of His, solution pH value and the existence of NH4Cl salt at the operating pressure and temperature. In connection with the operating conditions, properties of the research system and evaporation vessel geometry factors, a new mass transfer coefficient model, based on the dimensional analysis of experimental data, was proposed with relative error of ±10%. Check results showed that agreement between model predictions and experimental data is quite reasonable. The results obtained appear to be used to predict evaporation rate of histidine-water system for industrial reference.

Abstract: With the continuous improvement of power density,in the process of diesel fuel evaporation in cylinder, the interaction between droplets continues to grow. In order to study the mutual influence in the process of droplets evaporation, the evaporation phenomenas of single droplet, double-droplet and multi-droplet were studied experimentally in this paper. Firstly the influence of background temperature on single droplet evaporation rate was contrasted to verify the reasonableness of the experimental system. And then the influence of number of droplets and distance between droplets was compared and elicited the value of evaporation rate for each experimental condition. It can be found that when the number of droplets increases, the evaporation rate of droplets decreases; when the distance between droplets decreases, the evaporation rate of droplets also reduced.