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This study proposed an integrated system model for an original spray flash vacuum distillation system that enhances and leverages the thermal non-equilibrium of the flash process via active vapor extraction to realize an internal heat recovery feature, in which partial heat from hotter vapor is recovered to cooler spray residue within the same stage of feed circulation. This system contains four interlinked sub-systems: (1) an evaporation chamber in which a vacuum-promoted spray flash vaporization occurs, with an active vapor extraction and an outflow of evaporation-cooled brine, (2) a recirculation loop of feed-brine mixture, with the circulation pump, feed heater, and spray nozzle, (3) a hybrid dual-condenser combination, with the internal heat recovery from condensing vapor to the recirculating feed and a secondary cooling by an external coolant, and (4) a vacuum source that maintains vacuum conditions to the entire system as well as discharges the non-condensable gases. The pressure of vapor phase, as the major interlinked operation parameter, is in order of sequential decrease from the evaporation chamber, through condensers, to the vacuum source while the depressurization level in each sub-system is strongly coupled with other transport characteristics such as flash vapor generation in the evaporation chamber or condensing vapor flow in condensers. Thus, the integrated system model is composed of four sub-models to describe the key processes in such four sub-systems. For the modeling validation, a lab-scale experimental system is developed to provide relevant measurements. Comparisons between model predictions against measurements show a good match. Major process characteristics (such as spray flash rate, yield rate, and operating temperatures and pressures) and operational thermodynamic characteristics (such as thermal consumption and heat recovery efficiency) are investigated parametrically. The system's multivariate impacts concerning distillate yield rate and heat recovery effectiveness are also studied with varied operating parameters. Results indicate the pronounced thermal non-equilibrium feature arising from the spray flash process can be effectively utilized via the internal heat recovery design of our system to recover up to more than half of the heat from the yield vapor. Meanwhile, the developed system model can effectively analyze various operational and parametric effects, proving valuable for system design and optimized operation. • The system model integrates strongly coupled sub-systems and can effectively predict processing characteristics. • The thermal non-equilibrium of spray flash is utilized via the proposed design to improve thermal efficiency. • The system's yield rate and heat recovery effectiveness are positively related to the superheat level and feed flow rate. • The modeling algorithm and proposed sub-models can be served for multi-stage system's design and optimization. [ABSTRACT FROM AUTHOR]

Abstract The multiple-effect distillation (MED) technology is nowadays the most promising desalination process to be coupled with variable heat sources, thus leading to a more sustainable way to produce water. In order to prove the potential of this, it is of major interest to develop powerful modelling tools to predict the performance of this coupling. Only a few models have been presented so far. They show promising results but were based on some simplifying assumptions and non-physical constraints that could limit the analysis of the dynamic behaviour of a MED plant. This paper presents new considerations for the dynamic modelling of a MED plant associated with a thermal vapour compression unit, starting from a previous work "A dynamic model for MED-TVC transient operation". After several improvements, this model is now more representative of the real operating modes of a MED-TVC plant by considering real process inputs. This paper also highlights the importance of accurately modelling the interconnection between effects, the evaporation and condensation processes and the other components, such as the pre-heaters. Here is also presented a control strategy for operating a MED plant under dynamic conditions. Indeed, when a perturbation occurs in the motive steam pressure, it is possible to stabilize the whole plant by a simultaneous variation in the intake seawater mass flow rate at the final condenser. The model has been validated in steady-state conditions with experimental data from a MED-TVC plant operated in Trapani (Sicily) and was used to perform dynamic simulation to prove the feasibility of operating a MED-TVC plant under dynamic conditions, which is a major step toward proving the possibility of a coupling with renewable energies. Highlights • An equation-based dynamic model for MED-TVC has been implemented • The model is representative of the real operating modes of a MED-TVC plant by considering real process inputs • It also accounts for the modelling of the evaporation and condensation processes as well as the interconnection between two successive effects • Transient operations due to disturbances are analysed • Strategies for process control under variable regime are developed, based on the brine levels in the effects [ABSTRACT FROM AUTHOR]

Worldwide water scarcity signifies an urgent need to develop sustainable, simple to operate, low-cost, small-scale desalination units especially suitable for remote communities. The single effect distillation (SED) and the single stage flash (SSF) type low-pressure barometric desalination units satisfying the above requirements have attracted great interest in academic circles, but a comparison of the two has never been attempted. Thus, analytical models have been developed to identify and evaluate common performance indication parameters. The main results of the analysis show that the SSF unit's heat input rate is ~30% greater than that of the SED unit, with a resulting decrease in its performance ratio of ~24%, in comparison. Consequently, the brine heater area of the SSF is ~3.25 times the evaporator area of the SED. Furthermore, the seawater feed rate in the SSF is also about 20 times greater, leading to a 20 times larger release of non-condensable gases into its condenser. This additionally results in the SSF unit's ‘recovery factor’ of only 3.3%, as compared to ~67% in the SED unit. These results reveal that the solar-driven barometric SED type units have a considerably better performance in all comparison aspects over the SSF type units. [ABSTRACT FROM AUTHOR]

This work presents the design of a membrane distillation (MD) unit coupled to a refrigeration device. The operation of an MD pilot plant is first tested then simulated using EES solver. The range of hot water feed temperature provided by the condenser of the refrigeration device may vary from 25 to 65 °C as needed by the MD unit. The results of the experimental study enable to validate a 1D theoretical model with a maximum deviation of ± 6%. This model is combined to a heat pump model to simulate the operation of a coupled machine. The system performance is studied following two scenarios. In Scenario 1 (continuous mode), the system is connected to a seawater network. In Scenario 2 (batch mode), the seawater reservoir is filled up manually every day. The simulation study shows that the increase of the feed water temperature enhances significantly the produced permeate flux but decreases the performance of the heat pump. This system exhibits high exergy efficiency and GOR for a high feed water temperature. Exergy efficiency and gained output ratio (GOR) decrease as the water flow increases and the hot water temperature decreases. Conversely, the coefficient of performance (COP) of the refrigerator increases. [ABSTRACT FROM AUTHOR]

This paper presents an experimental work to study the effect of the condenser and the medium of saline water types on the performance of the solar still. Single slope solar still facing the south is used in this work. Also, four types of the condenser are tested: (i) glass, (ii) aluminum plate, (iii) aluminum heat sink with pin fins, and (iv) aluminum plate covered with an umbrella. Moreover, four mediums of the saline water inside the basin are examined: (i) only saline water in the basin, (II) Layers of black steel fibers in the basin, (iii) saturated sand with saline water, and (iv) mixture of sand and black steel fibers saturated with saline water. The solar still of only glass walls and only saline water in the basin is taken as a reference case. The performance of the other cases is referred to the reference case. The results indicate that using heat sink condenser increases the temperature of the saline water. Also, it increases the temperature difference between the condenser and the saline water relative to using glass condenser. Also, using a glass condenser with black steel fibers inside the water basin increases the daily productivity of freshwater by 35%. Using the heat sink condenser increases the daily productivity from 31% in the case of using only saline water to 52% in the case of using black steel fibers in the basin. Using an umbrella of 20 cm wide at the top of the aluminum plate condenser decreases the daily productivity by 26%. Increasing the umbrella wide to 40 cm decreases the daily productivity by 31%. [ABSTRACT FROM AUTHOR]

This work presents a modified solar still with pin fins absorber and external condenser. An experimental comparative study is carried out between the modified solar still with pin fins absorber and condenser, still with pin fins absorber and conventional still. This experimental study is conducted to evaluate the thermal behavior (evolutions of absorber and glass temperatures) and the water production performance of the modified solar still with pin fins absorber and condenser compared to other designs. All experiments are carried out under the meteorological conditions of the region of Gafsa-Tunisia during the days 01/26/2016, 01/27/2016 and 01/29/2016. Experimental results are presented, quantified and discussed to show the utility of the proposed modified solar still. [ABSTRACT FROM AUTHOR]

Although many adsorbent materials have been used in adsorption systems, only silica-gel was tested experimentally for desalination applications. This work experimentally and numerically investigates the use of CPO-27(Ni) an advanced Metal Organic Framework-MOF adsorbent material in a 1-bed adsorption system for water desalination and cooling applications. Operating parameters as switching time, half cycle time, evaporator and condenser water inlet temperatures were studied to investigate their effects on cycle water production and cooling. Moreover, a mathematical simulation model is developed, validated and used to predict cycle outputs at other operating conditions. Results showed that as evaporator temperature increases and condenser temperature decreases, cycle outputs increase. Also, it was shown that adsorption desalination cycles can work with condenser pressure lower than evaporator pressure as the cycle is an open loop one (i.e. no refrigerant is flowing back from condenser to evaporator). A water production of 22.8 m 3 /tonne·ads/day was achieved using 40 °C evaporator temperature, 5 °C condenser temperature and 95 °C desorption temperature. Similar water production can be achieved using 30 °C condensing temperature but at 120 °C desorption temperature. For space cooling applications (T evap < 20 °C), cycle cooling produced was found to be 65 Rton/tonne·ads. This work highlights the potential of using advanced MOF materials for water desalination/ cooling applications. [ABSTRACT FROM AUTHOR]

Solar still is one of the best solutions to solve water scarcity. The major drawback of the still is its low productivity. Improving the evaporation and condensation rate will increase the productivity of the still. In this work, a conventional and a modified single basin single slope solar stills were used for experimental analysis. Two single basin single slope solar still of same dimensions were fabricated. One of the still was attached with a provision to give agitation effect and external condensation. Agitation effect was given by a shaft coupled with a dc motor and an exhaust fan was used to extract the vapor from still to external condenser. Experimentation was carried out to compare the performances of conventional still and the modified still under same atmospheric conditions. The agitation effect breaks the surface boundary layer of water and increases the area of contact between the water and air. The exhaust fan and external condenser enhanced the circulation of air and condensation of vapor. The experimental result shows that the modified still enhanced the distillate productivity by 39.49% as compared to the conventional still. Also modified still is more economical than the conventional still. [ABSTRACT FROM AUTHOR]

Plastics have been the preferred choice of material for the commercial production of the solar stills. However, most of the currently available solar stills are either too big or too small for satisfying drinking water needs of a single family. Furthermore, methods for increasing the production of water from a solar still are often difficult and costly to integrate in a solar still. Here, we show the effect of adding a plastic channels as passive condenser on an inflatable solar still. The still has a basin area of 1.8 m 2 . The tests were performed in lab conditions at different water temperatures. The production of water achieved from the still at a water temperature of 73 ° C was 0.75 l/h. Furthermore, the production of water increased to more than 0.95 l/h with use of air flow over the the passive condenser to mimic wind or with use of wet tissue on the passive condenser to mimic evaporation cooling. [ABSTRACT FROM AUTHOR]

In this paper, a solar desalination system with humidification–dehumidification cycle consisting of a solar humidifier and a subsurface condensation mechanism designed for producing fresh or irrigation water is studied and numerically simulated. In this system, solar energy is used for providing the required heat and a set of tubes buried in the soil are used as condensers. Initially, in order to increase inflowing air humidity, seawater or any other brackish water is vaporized in a solar humidifier and then the humid air is passed through a set of tubes buried in the soil. Then the condensation mechanism takes place and fresh water is produced. Mass and energy balance equations for solar humidifier and subsurface condenser are used for thermodynamic analysis. The resulting linear and nonlinear equations are numerically solved for analyzing different parameters of the cycle and determining the amount of water produced. Finally, the sensitivity of the cycle's primary parameters was analyzed using design of experiment (DoE) method based on response surface method (RSM) in order to obtain optimal conditions. In addition different diagrams are presented to assist the designer to choose suitable design parameters based on the operational conditions. According to the design and numerical simulation, the rate of fresh water produced per underground pipe's length is 3.812153(kg/m . hr). [ABSTRACT FROM AUTHOR]

The availability of potable water and cooling are becoming increasingly important to ensure good sustainability and quality of life. In this work, a new multi-cycle adsorption desalination and cooling system using AQSOA-Z02 has been developed for high water production and cooling rates using renewable and waste heat sources. It consists of two 2-adsorber bed cycles linked with integrated evaporator/condenser, one cycle uses the integrated evaporator/condenser as evaporator (upper) and the second one uses it as a condenser (lower). In this system low condensing temperatures can be achieved using the cooling effect from the evaporator of the lower cycle and the integrated evaporator/condenser thus enhancing the system performance. Also, the adsorber beds of the upper and lower cycles are heated in series during the desorption process using the same heat source. This system can operate in three modes depending on the desalinated water and cooling capacity requirements. Results showed that the specific daily water production ranges from 6.64 to 15.4 m 3 /tonne adsorbent/day while the cooling capacity reaches up 46.6 Rton/tonne adsorbent at evaporator temperature of 10 °C. The new cycle offers potential of simultaneously producing large amounts of desalinated water and cooling capacity (at 10 °C) compared to other cycles. [ABSTRACT FROM AUTHOR]

Multi stage flash (MSF) desalination has proven to be the most reliable desalination technology for the Gulf region. As part of the continual quest for more sustainable and environment-friendly desalination technologies, this study investigates a proposed novel method for improving the thermodynamic and economic efficiency of MSF desalination. The proposed method has been tentatively named “brine extraction”. The technique involves extracting a part of the cooling brine from the water boxes and re-injecting this extracted brine directly into the flashing chambers; i.e. the extracted brine will not pass through the brine heater or high-temperature flashing stages. Economically speaking, brine extraction is expected to reduce the surface area of condenser tubes at the brine heater and high temperature flashing stages, and shift the vapor condensation heat load to lower temperature flashing stages, where a cheaper condenser tube material is used. More importantly, brine extraction is expected to reduce both the heating steam and the specific electrical power consumption of the MSF process. A computer model of conventional MSF desalination was constructed and verified against the currently operational MSF plant “Ayoun Mousa” located in Egypt. After the computer model was validated, a model of a 16.2 MIGD brine recirculation MSF plant was constructed and its performance was studied with and without the novel configuration named “brine extraction”. Single-point brine extraction, where a single stream of brine is extracted, performed better than multiple-point brine extraction, where multiple streams are extracted at multiple points. Single-point brine extraction is also favored because it will cause minimal increase in complexity and reduction in the robustness of the MSF process, as only a single stream of brine will be redirected. At the optimum extraction ratio of 9%, single-point extraction yielded a 7.23% increase in gain output ratio (GOR), a 3.47% decrease in electrical consumption, and a 3.90% decrease in total cost. Although the reduction in the cost of water is marginal, the reduction in electrical consumption and improved GOR indicate that the implementation of brine extraction at high top brine temperature (TBT) could be a promising technology in the case of solar-powered MSF, where the high expense of supplying thermal and electrical energy has been the most prohibitive factor. [ABSTRACT FROM AUTHOR]

In this article, a novel solar still which is equipped with thermoelectric modules to utilize the heat of vapor condensation is experimentally investigated. The use of thermoelectric modules as devices for generating electricity from the temperature difference between two environments (hot vapor steam and cold ambient air) as well as taking outstanding advantages of evacuated tubes as collectors with high performances in adverse climatic conditions, led to utilizing of the energy dissipated due to vapor condensation and a considerable increase in the performance of the system. The effect of using the generated electricity to operate a small propeller fan for inducing forced convection was examined. The results indicated that, by generating a forced convection, the water yield and hourly efficiency of the system increase and reach respectively to the maximum values of 1.11 kg/m 2 /h and 68%. In addition, the effect of two different depths for the water inside the evacuated tubes underwent experiments and it was observed that by filling the evacuated tubes, the output increases by 27% compared with the half-full case. [ABSTRACT FROM AUTHOR]

Abstract: Solar humidification–dehumidification (HD) desalination can be used for fresh water production from seawater in greenhouse. In this paper, a new design for an integrated system is proposed and evaluated to improve performance of fresh water production from seawater in greenhouse by two major changes: first, using a direct contact dehumidifier (DCD) instead of common indirect condensers and second, applying a more efficient and economical solar water heater (SWH) system. DCD can solve many problems of indirect condensers that are reported in previous studies. Also, for increasing driving force of mass transfer in DCD, an efficient SWHS increases the hot water temperature in the humidifier. Humidifier and dehumidifier were modeled and solved based on finite deference method. SWH system was dynamically modeled to predict the storage tank temperature at any time of the day and for various months of the year. The completed model, including the SWH system and the desalination unit, solved to estimate the fresh water production of the system. Results show that the proposed system can produce 6–22 (m3/day/ha) fresh water in various days of the year. Also it can solve many operational problems of the indirect condensers that can help the commercialization of this technology. [Copyright &y& Elsevier]

Abstract: Radiation-cooled dew water condensers can serve as a complementary potable water source. In order to enhance passive dew collection water yield, a Computational Fluid Dynamics (CFD) software, PHOENICS, was used to simulate several innovative condenser structures. The sky radiation is calculated for each of the geometries. Several types of condensers under typical meteorological conditions were investigated using their average radiating surface temperature. The simulations were compared with dew yield measurements from a 1m2 30°-inclined planar condenser used as a reference. A robust correlation between the condenser cooling ability and the corresponding dew yield was found. The following four shapes were studied: (1) a 7.3m2 funnel shape, whose best performance is for a cone half-angle of 60°. Compared to the reference condenser, the cooling efficiency improved by 40%, (2) 0.16m2 flat planar condenser (another dew standard), giving a 35% lower efficiency than the 30° 1m2 inclined reference condenser, (3) a 30m2 30°-inclined planar condenser (representing one side of a dew condensing roof), whose yield is the same as the reference collector, and (4) a 255m2 multi-ridge condenser at the ground surface provided results similar to the reference collector at wind speeds below 1.5ms−1 but about 40% higher yields at wind speeds above 1.5ms−1. [Copyright &y& Elsevier]

A novel concept of film distillation equipped with the membrane condenser (FD-MC) was proposed and implemented for the concentration of brine salt solutions. In this thermo-gradient method, the water was evaporated from the thin liquid film flowing alongside the hot surface, and then directly condensed on the cold surface of the porous membrane placed at the distance of few millimeters from the feed. The change of the membrane positioning from the hot feed solution to the cold water stream (coolant circuit) enables to overcome the common challenges of the membrane distillation process like long-term stability towards pores wetting, membrane scaling, and latent heat loss. Comparing with the air gap membrane distillation with membrane condenser (AGMD-MC), FD-MC demonstrated higher water flux (14.7 kg/m2·h) and stable performance during the concentration of NaCl solution from 50 up to 230 g/kg (microcrystal formation was noticed) even in the presence of organic pollutants (kerosene or surfactants). A mathematical model of heat and mass transfer in FD-MC process was proposed and successfully verified. With the respect to the temperature of hot (40–100 °C) and cold (10–60 °C) circuits, the energy consumption and thermal efficiency of FD-MC process were in the range of 2.7–3.2 MJ/kg and up to 97%, respectively. Unlabelled Image • Combination of film distillation and membrane condenser (FD-MC) was proposed for concentration of high salinity water. • Presence of organic pollutants (kerosene or surfactants) and high salt content do not affect FD-MC performance. • Mathematical model of heat and mass transfer in FD-MC process was proposed and successfully verified. [ABSTRACT FROM AUTHOR]

This experimental study aims to reveal the negative effect of the external condenser (EC) on the conventional solar still (CSS) performance. A new EC design was proposed and integrated into a single-slope, basin type CSS. The EC's negative aspect is demonstrated through a comparative study between the CSS and the modified solar still (MSS) in the same outdoor weather conditions. The experimental results show that adding an EC to the CSS is not always positive and the still performance is closely related to the weather conditions. The EC positive effect appears in moderate weather conditions, where its contribution to improving MSS productivity reaches 29%. While in very cold or hot weather days, the EC affects adversely the still productivity, which decreases to about 16.5% against that of the CSS. It was found that the natural circulation mode (NC) is the dominant mass transfer process, which contributes by about 63% to 80% to the water vapor transfer toward the EC. The results show also that the maximum daily energy and exergy efficiencies for the MSS and CSS are 23.2% and 1.9%, respectively, while for the CSS, they are 18.25% and 2.4%, respectively. • A new external condenser (EC) design was presented. • The effect of integrating an EC on conventional solar still (CSS) is experimentally studied. • Integrating an EC into CSS is not always efficient. • In moderate weather days, EC enhances the daily yield by about 29%. • In cold and hot weather, EC decreases the daily yield by about 4.24% to 16.53%. [ABSTRACT FROM AUTHOR]

The present study examined the performance of different modifications of identical solar stills (SSs) with heating/cooling and nanofluid. The first system is SS with thermoelectric heating (TEH) in the basin. The second system used TEH in the basin and loaded with nanofluid. The third SS used TEH as well as nanofluid and equipped with a double-slope symmetric external condenser that one side of it cooled by film of water and the other side with thermoelectric. Silver nanoparticle due to well-known characteristics in water disinfection was used with 0.03% weight. A series of experiment performed during one week in June 2019. Findings revealed that the daily yield and efficiency for SS with nanofluid/condenser and with nanofluid without condenser compared with SS without nanofluid/condenser improved by about 100.5%, 26.7% and 50.8%, 30.6% respectively. The highest productivity obtained by SS with nanofluid/condenser with 7760 cc/m2/day where the productivity from the glass-side increase by about 16.5% and 47.6% compared to SS with nanofluid without condenser and SS without nanofluid/condenser. Also it revealed that the contribution of external condenser in productivity is 26.3% of total productivity. Findings showed that the productivity of thermoelectric-side of condenser is more than 5 times higher than water film-side. • A modified solar desalination system with double-slope condenser and internal heater with nanofluid experimentally studied • Total yield and efficiency of SS with nanofluid and condenser is improved about 100.5% and 50.8% respectively. • The contribution of external condenser is 26.3% of total productivity. • Condenser increases the yield of glass-side while productivity of thermoelectric-side is 5.5 times higher than water-side. • Silver nanoparticle increased the rate of heat and mass transfer while it act as an anti-bacterial agent. [ABSTRACT FROM AUTHOR]

The impact of salty water medium and condenser type on the performance of single slope solar still is experimentally performed. Two solar still types are examined; conventional solar still with glass condenser (CSS) and solar still with plated finned heat sink condenser (MSS). The study is investigated for three saline water mediums in the still basin; pure saline water, sand saturated with saline water and steel wire meshes submerged inside the saline water. These stills are investigated in case of still only or still incorporated with parabolic trough collector (PTC) in hot and cold climate conditions of upper Egypt. Findings show that utilizing wire mesh, sand and heat sink condenser (HSC) raises the still freshwater yield and efficiency. The maximum freshwater yield rising in summer is 67%, 7.3% and 6% due to using PTC, HSC, and sand, respectively compared to CSS. The efficiency of all still systems in summer is found greater than winter. Moreover, utilizing HSC raises the still efficiency by 11.6% in summer and 8% in winter compared to CSS. MSS achieves the greatest efficiency of 41.95% in summer and 31.96% in winter while MSS+sand+PTC accomplishes the minimum freshwater cost with a decrease of 25.2% compared to CSS. • Impact of saline water medium and condenser type on the performance of solar still systems is considered. • CSS has the minimum still yield but, MSS+sand+PTC has the maximum yield. • Impact of utilizing HSC on the daily freshwater productivity in summer is greater than winter. • MSS achieves the maximum system efficiency of 41.95% in summer and 31.96% in winter. • Minimum cost of the freshwater is achieved in case of MSS with sand water and coupled with PTC. [ABSTRACT FROM AUTHOR]