Kg Of Fresh Water Research Articles

Thermoeconomic assessment of an adsorption cooling/desalination cycle coupled with a water-heated humidification-dehumidification desalination unit

Adsorption desalination (AD) and humidification-dehumidification desalination (HDH) technologies are attractive since they can be powered by low-grade energy sources and can be constructed on a small scale. This paper adopts a novel hybrid AD-(water-heated) HDH system to produce freshwater and cooling power, simultaneously. The system is mainly powered by a low-grade energy source (natural gas), while photovoltaic (PV) panels are used to run the auxiliary components such as pumps, and blowers. A detailed thermoeconomic model is developed to explore the effect of different parameters on the system performance and products’ cost. This analysis reveals that the system can deliver, at its optimal operating conditions, 21.75 kg of freshwater per hour for 1.15 ȼ/liter with a gained output ratio (GOR) of 2.50. The coefficient of performance (COP) and the cooling capacity of the proposed system are recorded at 0.46 and 2.53 kW, respectively. Besides, a comparison between the proposed hybrid system and a traditional standalone water-heated HDH unit is performed. This comparison shows that the GOR value of the hybrid system is always higher than that of the standalone HDH (about 350% increase). This trend indicates that the proposed system significantly improves overall performance. Considerable saving in the freshwater cost (from 30 to 40%) is also attained.

Thermodynamic balancing of the regeneration process in a novel liquid desiccant cooling/desalination system

This paper focuses on thermodynamic balancing of the regeneration process in a hybrid liquid desiccant cooling/desalination system. The thermal balancing technique is investigated by adding a single extraction between the system regenerator and condenser. This technique is considered as a potential method to reduce energy consumption and increase the hybrid system performance, dramatically. The mathematical procedure to model the proposed system using enthalpy pinch is outlined to study the effect of extraction on the hybrid system performance. The hybrid system, with a single extraction and without extraction (zero extraction), is analyzed in terms of the normalized entropy generation, local enthalpy losses, the coefficient of performance, and proper extraction location. The results show that at enthalpy pinch of 20 kJ per kg of dry air, single extraction system performance is 85.7% better than zero extraction. In addition, the single extraction produces 103.2 kg of fresh water per hour as a by-product compared to 94.2 kg per hour for the zero extraction system.

An innovative closed-air closed-desiccant HDH system to extract water from the air: A case for zero-brine discharge system

In a conventional HDH system, a constant feed of seawater is required to run the system. As a result of extracting freshwater from the saline water, it is rejected at higher salinity, thus it cannot be recirculated as a feed again. The aim of this study is to come up with a zero-brine discharge system that eliminates the continuous need for the supply of source and sink in the conventional system. Based on the fact that earth's atmosphere holds a vast amount of water that can be considered as a reliable freshwater resource, especially in coastal areas. A water-from-air system is proposed in this study. The proposed system configuration comprises of two parts, a basic HDH system that uses a liquid desiccant solution instead of saline water and a desiccant-based air dryer. The liquid desiccant leaves the HDH part at a higher concentration due to the extraction of freshwater. It then enters the air dryer where it is diluted by absorbing water vapor from the ambient air. This diluted desiccant is directed to the HDH part to close the desiccant loop. In this study, Lithium chloride is used as the working fluid of the proposed system. Mathematical modeling of heat and mass transfer processes between the air and desiccant in the humidifier and dehumidifier is developed to predict the performance of the desalination system. The proposed system produces about 8 kg of freshwater per hour.

Thermal type seawater desalination with barometric vacuum and solar energy

Abstract As well known, it cannot be denied that seawater desalination is the only commercial solution capable of breaking through the global water shortage. However, since seawater desalination is the process consuming a large amount of energy, saving energy to produce freshwater is extremely important in various seawater desalination processes. Energy consumption of desalination process is evaluated by the index called specific energy consumption (SEC), which means the energy for producing 1 kg of freshwater. For this reason, the renewable energies have been applied to the seawater desalination for energy saving. Usually, in such a case, the solar energies are adopted to heat seawater, and to transport seawater and freshwater. In this study, for the further reduction of the SEC, the passive vacuum pipe based on the hydrostatic head was applied. This study was mainly focused on the freshwater production rates with the height of a passive vacuum pipe. From the theoretical calculations, the freshwater production rate was over 7% of the supplied seawater when the height of a vacuum pipe is 9.8 m and the seawater temperature is heated to 80 °C. This evaporating percentage is very high compared to other conventional thermal type desalination process.

Thermodynamic analysis of an innovative liquid desiccant air conditioning system to supply potable water

Liquid desiccant air conditioning systems are cost-effective, environmentally friendly and energy efficient techniques, especially in coastal areas. In the conventional liquid desiccant air conditioning system, the scavenging air is expelled into the atmosphere carrying a considerable amount of energy and water vapor. Thus, there is plenty of room to improve the system performance by recovering these losses. The proposed system consists of a conventional liquid desiccant air conditioning system plus a condenser. The aim of this study is to reduce the energy consumption by recovering the heat from the scavenging air using the condenser while also producing freshwater in addition to space cooling. Lithium chloride (LiCl) is used as the liquid desiccant for this study. The mathematical formulation for simultaneous heat and mass transfer between the condenser and the regenerator was developed to establish a comparison between the performance of the conventional and modified systems. Using the generated model, it is found that the modified system performance is 11.25% better than the conventional system and that it produces 86.4kg of freshwater per hour as a by-product under the given conditions.

Comparing Winter and Summer Simulated Estuarine Circulations in Foxe Basin, Canada

Foxe Basin is an Arctic inland sea located at the north of the Hudson Bay system (Canada). The characteristics of its estuarine circulation in winter differ from those in summer, mainly because of the sea-ice formation and cover. Using Lagrangian tracers and flux calculations from simulated data through a section at the outlet of the basin, we have shown that one-third of all the ice produced in winter is eventually exported toward the Labrador Sea. Foxe Basin is also a place where, in winter, latent heat polynyas to the west coexist with sensible heat polynyas around southwestern Foxe Peninsula, the latter resulting from an upwelling of intermediate water approximately 0.6°C above the freezing point of seawater. Sea ice affects circulation in the basin by adding friction at the surface layer and by shielding the sea surface from the atmosphere, which leads to an average reduction of 11% in the surface currents. Sea ice also extracts approximately 1.3 × 1014 kg of fresh water from the sea surface. Divided by Foxe Basin's surface area (0.2 × 1012 m2) and by the freshwater density, this mass represents a mean layer of 0.65 m of fresh water. The salt transport anomaly versus depth at the outlet of the basin and the mean vertical buoyancy flux were also examined; this confirmed previous assumptions that the estuarine circulation forms a positive (summer)–negative (winter) couple. We suggest that the sensitivity of this couple to climate change may be used as a proxy to evaluate the impact of global warming in Foxe Basin. RÉSUMÉ [Traduit par la rédaction] Le bassin de Foxe est une mer intérieure arctique située au nord du système de la baie d'Hudson (Canada). Les caractéristiques de sa circulation estuarienne en hiver diffèrent de celles de l’été, principalement à cause de la formation et de la couverture de glace de mer. Au moyen de traceurs lagrangiens et de calculs de flux basés sur des données simulées à travers une section à la sortie du bassin, nous avons montré que le tiers de toute la glace produite en hiver est éventuellement exporté vers la mer du Labrador. Le bassin de Foxe est aussi un endroit où, en hiver, des polynies de chaleur latente à l'ouest coexistent avec des polynies de chaleur sensible autour du sud-ouest de la péninsule de Foxe, ces dernières étant produites par des remontées d'eau intermédiaire dont la température est approximativement 0,6 °C au-dessus du point de congélation de l'eau de mer. La glace de mer influe sur la circulation dans le bassin en ajoutant du frottement dans la couche de surface et en faisant écran entre la surface de la mer et l'atmosphère, ce qui provoque une réduction de 11% dans les courants de surface. La glace de mer extrait aussi environ 1,3 × 1014 kg d'eau douce de la surface de la mer. Divisée par la superficie du bassin de Foxe (0,2 × 1012 m2) et par la masse volumique de l'eau douce, cette masse représente une couche moyenne de 0,65 m d'eau douce. Nous avons aussi examiné l'anomalie de transport de sel en fonction de la profondeur à la sortie du bassin et le flux vertical moyen de flottabilité; cela a confirmé des hypothèses précédentes selon lesquelles la circulation estuarienne forme un couple positif (été) – négatif (hiver). Nous croyons que la sensibilité de ce couple au changement climatique peut servir d'indicateur pour évaluer l'impact du réchauffement planétaire dans le bassin de Foxe.

Thermal analysis for system uses solar energy as a pressure source for reverse osmosis (RO) water desalination

As Natural resources are becoming limited and energy price dramatically increased, energy utilization with efficient systems is essentially required to be used in desalination technologies. The use of solar energy in desalination processes is one of the most promising applications of renewable energies. The primary focus on desalination by solar energy is suitable for use in remote areas. A proposed desalination system uses solar radiation, which concentrated by parabolic dish to heat up the working fluid in a closed space. Then the generated pressure in this space used to push salt water into RO module.Daily production rate of fresh water quantity for suggested system compared with other solar techniques is a promising rate for each m2 of solar radiation collecting surface. The production rate for one operation cycle could reach to 1800L/cycle of fresh water at low water salinity (Brackish water with 5000ppm) and 55L/cycle at highest water salinity (sea water salinity with 42,000ppm). The required energy needed to produce 1kg of fresh water is also promising even when in case of using another type of energy, also operating cycle has ability of repetition according to salinity concentration through sunny hours.

Determination of rational design parameters of a multi-stage solar water desalination still using transient mathematical modelling

The paper describes the experimental investigations of the performance of a multi-stage water desalination still connected to a heat pipe evacuated tube solar collector with aperture area of 1.7 m 2. The multi-stage solar still water desalination system was designed to recover latent heat from evaporation and condensation processes in four stages. The variation in the solar radiation during a typical mid-summer day in the Middle East region was simulated on the test rig using an array of 110 halogen floodlights covering the area of the collector. The results of tests demonstrate that the system produces about 9 kg of fresh water per day and has a solar collector efficiency of about 68%. However, the overall efficiency of the laboratory test rig at this stage of the investigations was found to be at the level of 33% due to excessive heat losses in the system. The analysis of the distilled water showed that its quality was within the World Health Organization guidelines. The still's operation was numerically simulated by employing a mathematical model based on a system of ordinary energy and mass conservation differential equations written for each stage of the still. A computer program was developed for transient simulations of the evaporation and condensation processes inside the multi-stage still. Experimental results obtained and theoretical predictions were found to be in good agreement. The results on the determination of rational design dimensions and number of stages of the still for a given aperture of the solar collector are also presented in this work.

An Investigation into the Effects of Box Geometries on the Thermal Performance of Solar Cookers

The effect of box geometry, such as cylindrical and rectangular, on the performance of solar cookers has not been investigated. In this study, two different model box type solar cookers, which are in rectangular and cylindrical geometries, were constructed using the same material and were tested to investigate the effects of box geometries on the cooker performance. The experimental studies were conducted under the same operating conditions. The obtained results from the experiments were used to calculate the thermal efficiency and specific and characteristic boiling times. These parameters of the cookers were determined for 0.5, 1, and 1.5 kg of fresh water. It is observed that the cylindrical model has higher temperatures than the rectangular model under the same operating conditions. The thermal efficiency increased from 12.7 to 36.98% for cylindrical and 9.85 to 28.25% for rectangular model, when the quantity of water was increased from 0.5 to 1.5 kg; similarly, the characteristic boiling time was decreased from 39.56 to 14.35 for the cylindrical and 43.74 to 15.77 (min m−2 kg−1) for the rectangular model, respectively. The cylindrical model provided high thermal performance, which is indicated by high thermal efficiency and low characteristic boiling time, in comparison with the rectangular model.

Evaluation of energy recovery in reverse osmosis desalination plants

Desalination plants consume considerable amounts of energy for producing fresh water from seawater. Multistage flash (MSF) desalination plants require as high as 193–290 KJ per Kg of fresh water produced depending on the maximum operationg temerature. Reverse osmosis (RO) for seawater only consume about 43 KJ per Kg of fresh water produced. This energy requirements of RO plants can be reduced approximately by 40% if the energy of the pressurized energy recovery in RO plants. These include Pelton turbine, reaction turbine, hydraulic power recovery turbine and reverse running centrifugal pump. This paper will evaluate the feasibility of using these systems in RO plants for obtaining lower water production cost.