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In this work, we report the preparation of superhydrophobic and superoleophilic surfaces on stainless steel meshes by spray-coating of Cerium(IV) oxide (CeO2) nanoparticles obtained by a co-precipitation method. The synthesized particles and the coated meshes were characterized using advanced techniques. Scanning electron microscopy images showed the particles to be present in distinct lumps; merged with each other on calcination to give a homogeneous structure. Transmission electron microscopy analyses showed the agglomeration of individual particles to form the clusters. Contact angle measurements revealed the superhydrophobic and superoleophilic nature of the modified mesh surface in air. Fourier transform infra-red analyses of the synthesized particles showed the characteristics peaks of CeO2 found in commercial samples. X-ray photoelectron spectroscopy of the glass coated with ceria confirmed the predominant presence of Ce4+ that also explained the wetting behavior. Oil-water separation studies using a simple gravity-driven setup showed high separation efficiency of an oil water mixture. An analytical model is discussed in detail to account for the wetting behavior and efficacy of the prepared surfaces in separating the two fluids. To summarize, this work presents a very simple and effective route for oil-water separation with high efficiency.

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.

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.

Sulfate reducing bacteria (SRB) wreaks havoc in the oil industry by being an agent for oil souring and building corrosion in pipelines and thereby degrade the quality of crude oil. Palladium nanoparticles decorated silicon carbide nanomaterial (Pd-SiC) was synthesized by a facile single step synthesis process and this nanomaterial as a photo-catalyst, as compared to pure silicon carbide (SiC) nanoparticles showed a significant enhancement in the photo-catalytic efficiency in the process of the photo-catalytic deactivation of hazardous SRB. The morphological characterization studies such as Field emission scanning electron microscopy, Transmission electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy unambiguously revealed that SiC surface was successfully decorated with palladium (Pd) nanoparticles. Also the Pd nanoparticles decorated on the SiC surface was further substantiated by EDX and elemental mapping analysis, which clearly revealed the presence of Pd along with Si and O. The band gap energy estimated using Diffuse reflectance spectra (DRS) showed the reduction of band gap energy from 2.82 eV to 2.72 eV. The observed enhancement in the efficiency of photo-catalytic deactivation of SRB with Pd-SiC can be attributed to the significant reduction in the recombination of photo-generated charge carriers, characteristically resulting from the metal (Pd) semiconductor (SiC) junction established by this synthesis process.

This review focuses on the thermal-hydraulic performance correlations for the air-side of compact and microchannel heat exchangers. These correlations are presented in tables, mainly in terms of Colburn j-factor and fanning friction factor (f), based on each type of fin arrangements with appropriate constraints including Reynolds number ranges, geometrical parameter limits, and fitting uncertainties. The correlations used for air-side arrangements of mini/micro channels, which are constructed in slabs, are the same as those used for the compact heat exchangers. In particular, these correlations are used for louver-fin, wavy-fin, offset strip-fin, and extended surfaces (plain fins and pin fins) arrangements. However, the correlations proposed for fin-and-tube (round) are only valid for the compact heat exchangers. We have also compared some correlations with the experimental data of Kays and London standard reference. Some performance correlations are generalized (as one correlation for each j- and f-factor) to represent all louver-fin types. However, other fin arrangements have distinct correlations based on their specific geometry. The most reported correlations are valid for dry fin conditions, whereas there are limited correlations devoted to wet or frost surfaces. A guideline based on this study is provided to facilitate the use of correlations for various configurations.

In this study, exergo-economic analysis of two layouts of humidification-dehumidification (HDH) desalination systems driven by a vapor compression heat pump (HP) is presented and discussed. The systems are closed-air open-water water-heated cycle coupled with a heat pump (HP-HDH-WH), and modified air-heated cycles integrated with a heat pump (HP-HDH-AH). For the purpose of comparison, a conventional closed-air open-water (CAOW) electric water heated HDH system (E-HDH-WH) is also presented. Exergy destruction, exergetic efficiency and product cost are evaluated for these systems. The influence of input parameters such as mass flowrate ratio, dehumidifier effectiveness, compressor isentropic efficiency, and feed water temperature on second-law efficiency and exergy destruction associated with the major components of the systems are analyzed. The impact of input cost parameters is investigated using two different approaches. The analysis shows that evaporator and compressor are the components with the largest exergy destruction. The exergy efficiency for the HP-HDH air-heated unit, HP-HDH water-heated unit, and E-HDH water-heated unit is found to be 1.097%, 0.06965% and 0.05795%, respectively. The cost of desalinated water evaluated by current analysis for HP-HDH air-heated system, HP-HDH water-heated cycle, and E-HDH water-heated unit is found to vary from 4.61$/m3 to 5.49$/m3, 6.00$/m3 to 7.14$/m3, and 4.44$/m3 to 14.95$/m3, respectively. The results generally reveal that HP-HDH air-heated cycle shows better performance both from energetic and exergetic viewpoints.

Electrodialysis desalination (ED) is an efficient process to desalinate brackish water and to minimize brine salinities to the level of seawater salinity. From the many models reported in the literature, some are simple but have a limited accuracy while others are complicated with a good accuracy. In this context, we explore the improvement of a fundamentally ‘lumped’ model by considering the voltage drop at the interfaces between membranes and solutions (which is the so-called Donnan potential) while conserving the model simplicity. The present model is developed by accounting for an electrical resistance of the Donnan potential in the total cell pair resistance. The results are presented in terms of total membrane area, flow path length, number of stacks and specific energy consumption. The results show that the improvement resulting from involving the Donnan potential was substantial for a high difference between the feed and product salinities as well as for low salinities (

The differential equations of momentum and heat transfer are similar to each other based on some assumptions, leading to exact analogous equations. These analogies have since been the focus of attention and their applicability is explored in many fields and flow types. In some cases, these analogies hold valid even if the theoretical foundation is not available for such conditions. The Reynolds and Chilton-Colburn analogy are the focus of the current work, with four types of flow situations including, Couette flow, tube flow, parallel plate and flow over a flat surface. The numerical results show the best match for parallel flow and flat plate, while Couette flow resulted in large differences (by a factor up to 3.3).

Humidification dehumidification (HDH) systems are robust and known to withstand a wide range of saline water without the need of complex maintenance. In this study, the closed-air open-water (CAOW) HDH arrangement is examined, which can easily be integrated with solar or other renewable resources. Also, this system is modified by incorporating heat recovery options for low performing units. The heat recovery process is executed through two approaches, (i) a mixing chamber and, (ii) by a heat exchanger. Thermal balancing through air extraction is evaluated for the basic as well as the modified cycles, particularly for high performing units. Zero, single and double extractions models are evaluated for the conventional CAOW water heated cycle. The performance of the systems is characterized into three operating regions (high, moderate and low) based on the effectiveness of the components. Based on the results of this evaluation, an operating scheme is then developed to decide where to use the conventional or the modified systems with or without extraction.

Humidification dehumidification (HDH) desalination system is a thermal-based desalination technology that is suitable for small-scale water desalination applications. In this paper, we present an experimental and thermodynamic analysis of the energetic performance of two HDH cycles. The HDH cycles considered are the basic open-air open-water (OAOW) cycle and the modified closed-water open-air (CWOA) cycle with the options of brine recirculation. An experimental investigation is performed on the modified cycle to validate the theoretical model that is used to assess the energetic performance of both the basic and modified cycles. The theoretical model is found to be in a good agreement with the experimental data with a maximum percentage deviation of 5% from the experimental data. Furthermore, limiting cases of the system are explored. Within the limiting cases, the modified cycle recorded about 100% improvement in the energy performance over the basic cycle due to heat recovery process associated with the modified cycle. Additionally, a cost analysis was performed to determine the cost of freshwater production by the presented desalination cycles. Results show that the freshwater price varied from 4.10 to 6.55 $/m3 and 0.79 to 2.25 $/m3 for the basic OAOW HDH cycle and the modified CWOA HDH cycle, respectively.

Recently, recommender systems are getting popular in the e-commerce industry for retrieving and recommending most relevant information about items for users from large amounts of data. Different stochastic gradient descent (SGD) based adaptive strategies have been proposed to make recommendations more precise and efficient. In this paper, we propose a fractional variant of the standard SGD, named as fractional stochastic gradient descent (FSGD), for recommender systems. We compare its convergence and estimated accuracy with standard SGD against a number of features with different learning rates and fractional orders. The performance of our proposed method is evaluated using the root mean square error (RMSE) as a quantitative evaluation measure. We examine that the proposed strategy is more accurate in terms of RMSE than the standard SGD for all values of fractional orders and different numbers of features. The contribution of fractional calculus has not been explored yet to solve the recommender systems problem; therefore, we exploit FSGD for solving this problem. The results show that our proposed method performs significantly well in terms of estimated accuracy and convergence as compared to the standard SGD.

Humidification-dehumidification is a carrier gas based thermal technique that is ideal for small-scale water desalination applications. One advantage of humidification-dehumidification systems is the ability to utilize low grade and renewable energies as heat source to drive the system. This work presents theoretical investigation of humidification-dehumidification desalination system operated by a heat pump. The model is based on the first law of thermodynamics, describing heat and mass transfer in the combined humidification-dehumidification-heat pump cycle. The model predicts the performance of closed-air open-water water-heated, and modified air-heated cycle coupled with a heat pump. To improve the Gain output ratio and energy recovery of the system, a heat pump is used as the source of heating and cooling for the humidification-dehumidification desalination system. Energy rejected in the condenser is used as a source of heat in the humidifier whereas the cooling effect of the evaporator is used to cool incoming seawater for effective condensation of humid air in the dehumidifier. A parametric study is conducted to investigate the influence of system operating parameters, including water and air flowrate, seawater temperature, and refrigerant flow rate on the system performance. Results indicate a maximum Gain output ratio of 8.88 and 7.63 obtained at 80% components effectiveness and mass flow rate ratio of 0.63 and 1.3 for modified air heated and water heated cycle, respectively. A maximum gain output ratio greater than 10 can be achieved for humidifier and dehumidifier effectiveness of 100% leading to more energy efficient systems. The cost of desalinated water production is calculated and the effect of major parameters on its variation is also presented.

The analysis for fin thermal performance under dehumidifying conditions is conducted using a numerical approach. Finite-Element method is used to account for the non-linear effects due to temperature dependent parameters and humidity-temperature relationship. The temperature profiles, as well as the overall fin efficiency, are studied. The fin efficiency is found to be highly dependent on the operating conditions and the degree to which the heat transfer coefficient is a function of temperature. It is found that the effect of temperature-dependent thermal conductivity on fin performance is less as compared to heat transfer coefficient over the considered range of operating conditions.

In this paper, strength of fractional adaptive signal processing is exploited for parameter identification of control autoregressive autoregressive (CARAR) systems using normalized version of fractional least mean square (FLMS) and its recently introduced modification of type 1 and 2. The adaptation performance of the proposed normalized FLMS methods is compared with standard counterparts for CARAR identification model by taking different noise levels as well as fractional orders. The results of the statistical analyses are used to validate the consistency of the proposed normalized fractional adaptive methodologies in terms of convergence, accuracy and robustness. The reliability and effectiveness of the design schemes is further validated through consistently approaching the desired identification parameters based on performance metrics of mean square error, variance account for and Nash–Sutcliffe efficiency.

The current study provides a detailed analysis of multi-effect mechanical vapor compression desalination systems. Three different feed flow arrangements including forward-feed (FF), parallel-feed (PF) and parallel-crossfeed (PCF) are analyzed and compared in terms of energy consumption, exergy destruction, heat transfer area and product cost. For this purpose, energy, exergy, and economic models are simultaneously solved numerically. In this regard, a component-based exergo-economic model is used to calculate the fresh water cost. It is observed that FF has the highest energy consumption followed by PF and PCF. While, the heat transfer area is calculated to be the highest for PCF followed by PF and FF, respectively. Finally, the product cost is estimated to be 0.867 for FF, 0.865 for PCF, and 0.842 $/m3 for PF MVC systems operating with 4 evaporators.

Electrodialysis desalination plants, for brackish water, are designed based on different parameters such as feed concentration, current density, and stack construction. Among the various model assumptions, the constancy of the equivalent conductivity of the diluate and concentrate streams is considered a prominent one. In this paper, this assumption is relaxed at different levels and closed-form solutions are obtained to ascertain its effects. It is shown that previously published results can be replicated. Also, a comparison between the lumped and staged model shows that using the inlet flow rate in the lumped model instead of the product flow rate provides more accurate results. Further analysis reveals a non-dimensional number, termed the electrodialytic Biot number, which is the ratio of the total to exit concentration based average cell pair volume resistance. It was found to be physically equivalent to the number of stacks. This provided a clear criterion as to when the lumped model should be used. Specifically, as long as the electrodialytic Biot number is (less than or) equal to 1, the lumped model should be used, otherwise the staged model is a more appropriate choice. It also provides direction for future research. A design chart is also developed to facilitate the calculation procedure.

The paper presents an exergo-economic analysis of humidification-dehumidification (HDH) desalination system operating under a conventional open-water open-air (OWOA) and a modified closed-water open-air (CWOA) configuration. Besides, the possibility of coupling a reverse osmosis (RO) system with HDH unit is also analyzed. The hybrid HDH-RO system is studied under three different retrofits including a simple HDH-RO, HDH-RO with a Pelton turbine and HDH-RO with a pressure exchanger. The analysis reveals that the modified cycle has a higher exergetic efficiency and lower product cost than the basic cycle. The product cost for the basic cycle with an electrical heater is calculated to be $6.56/m3 and with the solar heater $5.98/m3. Moreover, it is observed that the hybrid HDH-RO system with a pressure exchanger has the highest gained output ratio and second-law efficiency followed by HDH-RO with a Pelton turbine and simple HDH-RO, respectively. The product cost for hybrid HDH-RO with a pressure exchanger is calculated to be $0.13/m3 and $0.12/m3 with an electrical and solar heater, respectively.

For oil-water separation, micron-sized stainless steel membranes were fabricated by spray-coating using dispersions of ytterbium oxide (Yb2O3). The operational parameters such as particles concentration and annealing temperature were optimized to achieve the best separation efficiency. Scanning electron microscopy (SEM) images of (Yb2O3) particles revealed that annealing at 200 °C results in sharp-edged grains that are uniformly distributed on the surface. These findings were further corroborated by X-ray diffraction (XRD) and selected area electron diffraction (SAED) analyses that confirmed the highest degree of crystallinity for the particles annealed at 200 °C. The analyses with Fourier Transform Infra-Red (FTIR) spectroscopy showed that annealing does not alter the bonding chemistry of the particles. SEM of the surface-modified membrane showed that the particles completely cover the target surface and are distributed uniformly. Wettability studies with water and oil clearly demonstrated that the membranes coated with Yb2O3 particles acted to be simultaneously superhydrophobic (contact angle of ~ 150°) and superoleophilic (near-zero contact angle). By measuring water contact angle of coated membranes annealed at different temperatures, a relationship between crystallinity and hydrophobicity was also established. These findings were reflected in oil-water separation studies performed under gravity where the modified membrane allowed all of the oil to pass through but completely blocked the water having a separation efficiency close to 100%. This efficiency was maintained after repeated cycles of oil-water passage confirming the stability of the coating.

Fractional adaptive algorithms have given rise to new dimensions in parameter estimation of control and signal processing systems. In this paper, we present novel fractional calculus based LMS algorithm with fast convergence properties and potential ability to avoid being trapped into local minima. We test our proposed algorithm for parameter estimation of power signals and compare it with other state-of-the-art fractional and standard LMS algorithms under different noisy conditions. Our proposed algorithm outperforms other LMS algorithms in terms of convergence rate and accuracy.

Assessment of desalination plants is essential to evaluate potable water production, energy consumption, and economic feasibility. A design model with a boundary layer effect, water transport effect, spacer effect, and Donnan potential was used for ED desalination. Similarly, a design model is also investigated for RO desalination with and without a pressure energy recovery device. Specific product water cost is evaluated based on annual expenses consisting of energy cost, fixed cost, labor cost, membrane replacement cost, maintenance cost, chemical cost, and insurance cost. Normalized sensitivity analysis is also conducted to identify the most influential parameters impacting the cost model. It is found that ED is economically feasible when salinity is less than 7 and 9 ppt compared to RO with and without PX, respectively. The product water cost is 0.384, 0.46, and 0.494 $/m3 for ED, RO with PX, and RO without PX, respectively, at a salinity of 5 ppt (e.g., groundwater salinity). The product water cost increases to be 1.532, 0.559, and 0.857 $/m3 for ED, RO with PX, and RO without PX, respectively, at a feed salinity of 35 ppt (e.g., seawater salinity). Also, highly saline water can be desalinated with ED at the cost of

It is reported in the literature that Electrodialysis Desalination (ED) is the most efficient for groundwater ( 9.5 ppt. The net recovery ratio for the hybrid ED-RO plant is 87.5% when ED and RO plants operate at a recovery ratio of 75% and 50%, respectively. For typical conditions and brackish water salinity of 5 ppt, ED-RO shows an outstanding performance of 0.731 kWh/m3 for energy consumption and 0.370 $/m3 for water cost. These values are better than those of standalone RO and ED plants.

The number of baffles has an impact on the thermal-hydraulic performance of a shell-and-tube heat exchanger (STHX), thus a model was developed using Engineering Equations Solver software to solve t...

The paper presents an exergo-economic based design and analysis of a forward-feed multi-effect mechanical vapor compression desalination system. The analysis is focused on estimating the energy consumption, exergy destruction, Second Law efficiency, and product cost for a different number of evaporation effects. In addition, a detailed heat exchanger design is also presented to estimate the heat transfer coefficients, areas, and pressure drop in the evaporators and feed preheaters. Finally, the cost flow diagram is provided to highlight the monetary cost of each stream as well as product cost which is compared with a conventional method. The values of specific energy consumption, Second Law efficiency and product cost from the current analysis are observed to be ranging from 7.67 to 11.36 kWh/m3, 7 to 11%, and 0.86 to 1.19 $/m3, respectively. Furthermore, the effect of a number of evaporators, compressor efficiency, evaporation temperature, interest rate, cost index factor and unit electricity cost on the plant performance is also discussed in the paper.

The current study is focused on thermoeconomic analysis of a single effect mechanical vapor compression (MVC) desalination system operating with and without brine recirculation. For this purpose, first- and second-law analyses are carried out to estimate the energy consumption and second-law efficiency of the plant. A single stage seawater reverse osmosis plant is also presented for the sake of comparison. For thermal systems, a detailed heat exchanger design is provided to calculate an overall heat transfer coefficients, heat transfer areas, and the pressure drops on the cold- and hot-sides of the heat exchangers. Besides, the product cost is calculated and compared by using two different cost estimation methods. Moreover, it is demonstrated that the cost-flow method of economic analysis is more elaborative and useful because it enables the component level cost optimization. The calculations reported the values of specific energy consumption (SEC), second law efficiency and product cost to be 10 to 13 kWh/m3, 8 to 9% and 1.7 to 2.3 $/m3, respectively. Furthermore, it is shown that the input parameters like cost index factor, electricity cost, compressor efficiency and the heat transfer areas have a remarkable influence on the product cost and must be selected carefully for accurate cost estimation.

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 86.4 kg of freshwater per hour as a by-product under the given conditions.

The flow distribution from a manifold to tubes occurs in the tube side of a shell and tube heat exchanger. The tubes increase the contact surface area thus improving the thermal performance, with an accompanied pressure loss due to the split and smaller hydraulic diameter after the split. The surface conditions of uniform temperature and heat flux are examined. Additionally, the manifold is subjected to the same thermal conditions to examine the impact on thermal-hydraulic performance. Three layouts are being considered, including a single tube, 4 tube, and 37 tube system. It is found that for a combined manifold and tube heating, a non-axisymmetric flow exists in the smaller tubes. To accommodate such flow behavior, it is recommended to define the thermal axis at the minimum temperature for each cross-section, to calculate the peripheral Nusselt number distribution. This procedure is applied to different channel geometries subjected to non-axisymmetric inflow from the heated manifold. All the computed results presented in this paper are also validated against the results available in the literature.

The presence of non-uniformities in the channels of a heat exchanger due to poor design of manifold and channel parameters has been the focus of the present paper. Unequal flow distribution results in an increased flow resistance leading to increased pumping power. It also leads to an imbalance of thermal characteristics due to the different mass flow rate in individual channels. The influence of manifold design, channel design, the location of inlet and outlet connections to the heat exchanger along with the use of secondary header has been discussed for both single and two-phase flow. The current achievements in the analytical modeling of such flow distributing manifolds have also been discussed supporting the numerical and experimental literature. In general, larger manifold area and a longer channel length are found to be resulting in better flow distribution. The use of secondary header results in higher pressure loss but this loss is offset by the increased flow uniformity. Two-phase flow behavior in distributing manifold is experimentally determined to be slug flow as a dominating behavior with occasional reverse flow. These non-uniformities must be taken into consideration for the proper design of heat exchangers, thus improving the performance of thermal systems.

A typical humidification dehumidification desalination (HDH) system operates at ambient pressure. However, the current work presents an HDH system that works at different pressures in order to improve its performance. The system parameters are optimized to maximize the Gain Output Ratio (GOR). In addition, the effect of the mass ratio, pressure ratio, effectiveness of components, and the maximum temperature of the system is studied. It is found that for an effectiveness of 0.8 and humidifier pressure of 50 kPa, a maximum GOR of 3.8 is obtained at a pressure ratio of 1.33 (GOR value of 8.2 is obtained for the effectiveness of 0.9). Sensitivity analysis is also performed to determine the main parameters that affect the system performance. It has been found that GOR is more sensitive to the pressures of humidifier and dehumidifier (32% contribution of pressure on the GOR among the variables considered). In addition, an exergy analysis is performed to determine the parameters that result in higher exergy destruction in the system. It is found that increasing the pressure ratio increases the irreversibility while maximum temperature has no effect on exergy destruction up to 60 °C.

This paper presents the experimental performance of a cross-flow packed-bed humidifier. In this humidifier, hot water is sprayed over packing material where air flows though it in a cross flow arrangement. The air is heated and humidified while flowing through the humidifier duct. The humidification capacity, saturation efficiency, and specific energy consumption are calculated using the experimental data of the inlet and outlet conditions for both air and water streams. The variation of these performance indicators with the mass flow rate ratio of water-to-air, the water inlet temperature, and the packing volume; is investigated. It was found that the specific energy consumption is almost constant with variation of the mass flow rate ratio, packing thickness, and water inlet temperature within the investigated range of these parameters. An effectiveness model originally developed for cross-flow packed-bed cooling tower is adopted to estimate the effectiveness of the humidifier. In addition, the effectiveness and the number of transfer units of the humidifier are determined using the experimental data. The model was found to be in a good agreement with the experimental measurement at high capacity ratio with a deviation of 6%. However, the model underestimates the effectiveness at lower capacity ratio with a maximum deviation of 30%.

In this article, we report effect of surface coatings on organic fouling in reverse osmosis (RO) desalination membranes at the two operating pressure extremes of 20.7 and 55.2 bar. The surface of commercial RO membranes was modified by depositing surface-enriched zwitterionic films in order to achieve enhanced organic fouling resistance. Antifouling performance of both the surface-modified and bare (uncoated) RO membranes was evaluated under cross-flow filtration conditions in the presence of sodium alginate (SA). Filtration studies of the model organic foulant solution showed that both reversible and irreversible flux declines were significantly lower and, as a result, considerably higher flux recovery was achieved after simple hydraulic flushing in the surface-modified membranes when compared to virgin RO membranes. The FE-SEM analysis revealed that foulant deposition on the surface of the modified membranes was patchy/irregular and porous in structure at both lower and higher pressures as opposed to dense and continuous foulant deposition with full coverage of bare membranes with SA at both low and high operating pressures. FTIR scans also qualitatively confirmed a higher amount of SA deposition and revealed that the foulant deposition is further enhanced at higher operating pressure of 55.2 bar on the surface of bare membranes.

Thermal performance characteristics of orthotropic material annular fins subjected to dehumidifying operating conditions are studied using two-dimensional finite element method. The method accounts for non-linear temperature–humidity ratio psychrometric relationship under both partially and fully wet operating conditions. Limits of one-dimensional solutions for orthotropic material fins subject to dehumidifying conditions are investigated in somewhat more detail by introducing dimensionless parameters. The dry fin parameter that fully governs fin efficiency under a set of operating conditions is also defined. The optimum fin dimensions are also estimated for a set of operating conditions and fixed fin volume.

A counter-flow heat exchanger with longitudinal conduction in separating wall is analyzed along with external heat flux. The inhomogeneous system of model equations is solved with the method of variation of parameters. Closed-form expressions are obtained for balanced flow with three types of wall end-conditions and the zero heat in-leak limit verified against reported expressions. In addition, analytical solution is derived for the general unbalanced flow model with non-adiabatic wall ends that is validated against the limiting case of no axial conduction. It enables examining property variations and arbitrary external load by dividing the system into smaller segments and applying the derived expressions to each element. Heat in-leak has higher impact on deterioration in the low NTU region studied when directed toward the hot fluid. As the external parasitic enhances with NTU, a critical NTU is noted in the range 2.8–5.1 for the various cases analyzed. At this optimum condition, the net energy reaching colder stages is between 27% and 55%.

The current study is focused on carrying out exergo-economic analysis of a seawater reverse osmosis (SWRO) desalination plant. The main objective is to compare the performance as well as the product cost of an existing SWRO plant, including post-treatment and distribution sections, for four different retrofit options made by coupling high-efficiency pressure exchangers (PXs) in place of conventional energy recovery turbines. For this purpose, first- and second-law analysis is carried out to estimate the energy requirements and second-law efficiency for each retrofit option. Finally, the product cost is compared by performing an exergo-economic analysis using appropriate seawater properties for the calculations. The analysis revealed that, by introducing a PX, the specific energy consumption (SEC) can be reduced by about 24%; thus, increasing the second-law efficiency. Besides this, it is also demonstrated that the addition of post-treatment and distribution sections enhances the product cost by almost 20%. Furthermore, the study suggested that using a booster pump with a PX (as used in retrofit # 3) is best suited for enhancing the plant capacity compared to retrofit # 4 in which a PX is used in place of the pump. It has the least product water cost among all the options discussed.

Speaker diarization systems aim to find &lsquo, who spoke when?&rsquo, in multi-speaker recordings. The dataset usually consists of meetings, TV/talk shows, telephone and multi-party interaction recordings. In this paper, we propose a novel multimodal speaker diarization technique, which finds the active speaker through audio-visual synchronization model for diarization. A pre-trained audio-visual synchronization model is used to find the synchronization between a visible person and the respective audio. For that purpose, short video segments comprised of face-only regions are acquired using a face detection technique and are then fed to the pre-trained model. This model is a two streamed network which matches audio frames with their respective visual input segments. On the basis of high confidence video segments inferred by the model, the respective audio frames are used to train Gaussian mixture model (GMM)-based clusters. This method helps in generating speaker specific clusters with high probability. We tested our approach on a popular subset of AMI meeting corpus consisting of 5.4 h of recordings for audio and 5.8 h of different set of multimodal recordings. A significant improvement is noticed with the proposed method in term of DER when compared to conventional and fully supervised audio based speaker diarization. The results of the proposed technique are very close to the complex state-of-the art multimodal diarization which shows significance of such simple yet effective technique.

Fractional calculus extends the scope of adaptive algorithms supporting the design of novel fractional methods that outperform standard strategies in various applications arising in applied physics and engineering. In this study, a momentum fractional least-mean-square (M-FLMS) algorithm for nonlinear system identification using a first and fractional-order gradient information is proposed. The M-FLMS avoids being trapped in local minima and provides faster convergence than the standard FLMS. The convergence and complexity analysis of the M-FLMS are given along with simulation results of a benchmark nonlinear system identification problem. The M-FLMS accuracy is verified through a parameter estimation problem for a nonlinear Hammerstein structure, modeling an electrically stimulated muscle (ESM) for rehabilitation of paralyzed muscles. The proposed method is studied in detail for different levels of noise variance, fractional orders and proportion of gradients used in the current update.

The application of compressed sensing (CS) to biomedical imaging is sensational since it permits a rationally accurate reconstruction of images by exploiting the image sparsity. The quality of CS reconstruction methods largely depends on the use of various sparsifying transforms, such as wavelets, curvelets or total variation (TV), to recover MR images. As per recently developed mathematical concepts of CS, the biomedical images with sparse representation can be recovered from randomly undersampled data, provided that an appropriate nonlinear recovery method is used. Due to high under-sampling, the reconstructed images have noise like artifacts because of aliasing. Reconstruction of images from CS involves two steps, one for dictionary learning and the other for sparse coding. In this novel framework, we choose Simultaneous code word optimization (SimCO) patch-based dictionary learning that updates the atoms simultaneously, whereas Focal underdetermined system solver (FOCUSS) is used for sparse representation because of a soft constraint on sparsity of an image. Combining SimCO and FOCUSS, we propose a new scheme called SiFo. Our proposed alternating reconstruction scheme learns the dictionary, uses it to eliminate aliasing and noise in one stage, and afterwards restores and fills in the k-space data in the second stage. Experiments were performed using different sampling schemes with noisy and noiseless cases of both phantom and real brain images. Based on various performance parameters, it has been shown that our designed technique outperforms the conventional techniques, like K-SVD with OMP, used in dictionary learning based MRI (DLMRI) reconstruction.

Humidification-dehumidification (HDH) is a cost-effective thermal desalination system that utilizes low-grade energy to extract freshwater from high salinity seawater with minimum maintenance. A robust method is presented using an innovative definition for energy effectiveness to facilitate the practical utilization of HDH modeling in the design process. This definition is mainly based on representing the flow stream on the temperature-enthalpy diagram to locate the pinch point and overcome the terminal-based definition limitation accordingly. The possible violation of the Second Law of Thermodynamics is the main drawback of the previous definitions due to the temperature-cross inside the humidifier, which defeats the purpose of air heating and humidification. The closed-air open-water HDH model is examined thermodynamically, and its design characteristics are explored at different operating conditions. The proposed definition is compared with analogous data from the literature. It showed an excellent agreement with a maximum discrepancy of 2.30%. Furthermore, a direct and straightforward design scheme is provided to estimate the dehumidifier and humidifier sizes based on the location and amount of freshwater needed. A case study for a system that produces 5 kg h−1 of freshwater in Dhahran is presented. The optimal energy effectiveness is found to be 78%, where the average minimum and maximum temperature of seawater in the system are assumed to be 25 and 70 °C, respectively.

A novel hybrid system consists of an efficient humidification-dehumidification (HDH) desalination unit driven by an absorption (AB) heat pump. A thermodynamically-balanced HDH unit with multiple air extractions is used, while single- and double-effect absorption (SEAB and DEAB, respectively) heat pumps are considered. The proposed systems are examined for simultaneous production of desalinated water and cooling effect under a fixed cooling load of 5 kW. As observed, the SEAB-HDH unit can produce up to 152.4 kg/h of desalinated water at a GOR value of around 10, for 0.002–0.0058 $/l. While the DEAB-HDH system delivers water of up to 135.4 kg/h for 0.0026–0.0098 $/l, at a GOR value approaching 15. Besides, COP values of about 0.50 and 0.81 are recorded for the SEAB- and the DEAB-HDH systems, respectively. It is noted that the DEAB-HDH system always supersedes the SEAB-HDH system in both GOR and COP values. An enhancement of over 100% in the GOR value is observed when air extraction is applied. Also, it is noted that single and double extractions improve water production by about 110 and 90%, respectively. A jump of nearly 500% is recorded in the water production when the cooling capacity increases from 2 to 15 kW. This jump is accompanied by a rise of 60 and 80% in the GOR and COP values, respectively. Finally, the theoretical GOR limit of the proposed systems is estimated.

The paper presents an integrated solar-driven desalination plant. It consists of an adsorption desalination (AD), a humidification-dehumidification (HDH) desalination, and two ejectors. The HDH unit reuses the silica gel AD cycle's waste energy to enhance the proposed integrated system's freshwater production rate. Two ejectors are also installed to improve freshwater productivity further. Two configurations are studied: with and without condenser/evaporator heat recovery (HR) circuit. In this regard, mathematical energy and cost models are built to examine the performance of solar-powered hybrid desalination systems installed in Assiut, Egypt, at different operating parameters. The model is validated against the available results in the literature. The solar irradiation, ambient temperature, adsorption cycle time, and HDH air mass flow rate on the cycle performance are studied. The highest freshwater is produced when the ratio between the mass flow rate of feed saline water and the air is about 1.4. When HR is applied, the specific daily water production (SDWP) reaches 83.1 m3/ton in June with a gained output ratio (GOR) of 2.7. The cost analysis shows that the specific cost of freshwater produced from the proposed desalination plant using HR loop is about $1.49/m3 when Solar Energy runs the proposed system. This particular water cost could decline to $0.54/m3 when waste heat is used.

In this study, a novel hybrid desalination/cooling system is investigated. The system combines a triple-effect absorption (TEAB) heat pump (whose working fluid is LiBr/water solution) and a water-heated humidification dehumidification (HDH) desalination unit. The system is investigated for simultaneous production of freshwater and cooling effect. A low-grade energy source (natural gas) is utilized to operate the system, while solar PV panels are used to power the auxiliary components of the system, such as pumps and blowers. A detailed mathematical model is established to explore the influence of different parameters on the thermodynamic and economic performance of the system. From the HDH unit’s side, it is observed that the effectiveness of the HDH components (dehumidifier and humidifier), the mass flow rate ratio, and the inlet conditions of the saline water have a considerable impact on the system performance. On the other hand, from the TEAB system’s side, the performance of the hybrid system is found to be significantly affected by the effectiveness of both the solution heat exchangers and the absorber. The results reveal that the system can produce, at its optimal operating conditions, 10 kg of fresh water per hour for 0.85 ȼ/l with a gained-output-ratio (GOR) value approaching 5.0. Additionally, the system can produce a cooling capacity of about 2.0 kW at a coefficient of performance (COP) value close to 1.5. Furthermore, the proposed TEAB-HDH system shows comparable performance to other heat-pump-powered HDH systems available in the literature.

The humidification-dehumidification (HDH) desalination is a favorable option for small scale and off-grid applications. Its main disadvantage is the low thermal efficiency compared with other thermal desalination techniques. This study demonstrates the importance of using the thermodynamic balancing concept in enhancing the thermal efficiency of HDH systems. An experimental HDH setup has been built to produce 276 kg of pure water per day (peak capacity) costing 0.033 $/L. The physical understanding of the balancing concept is clarified by representing the experimental results on the temperature enthalpy diagram. The enthalpy pinch model can be solved numerically, analytically, or pseudo-analytically to estimate the performance at the balanced conditions (upper limit of performance). Moreover, a novel parameter, dimensionless enthalpy pinch ( Ψ ¯ ) is proposed to be a measure of the thermal efficiency and a size index. The theoretical model has been validated against the experimental results with a maximum error of 6%. It can be concluded that adjusting the operating conditions to balance the system thermodynamically can improve economic performance by about 40%. Moreover, theoretically, the parametric study shows that the dehumidifier Ψ ¯ is more dominating on the gain output ratio (GOR) than the humidifier Ψ ¯ . Also, at a fixed Ψ ¯ , the maximum ( T max ) and minimum ( T min ) temperature influences the GOR significantly only at a low enthalpy pinch value ( Ψ ¯ ) where decreasing T max or increasing T min has a positive effect on the GOR.

Electrodialysis (ED) desalination is best-suited for groundwater. The groundwater comprises divalent and monovalent ions and radicals, such as Na+, Cl−, Mg2+, SO42−, Ca2+, K+, and HCO3−. Therefore, it is vital to conduct entropy generation analysis using a multi-component instead of a conventional binary NaCl solution. The current study evaluates and compares entropy generation in various zones of ED cell pairs using groundwater (multi-component) and NaCl solution with equivalent concentration by mass. Multi-component saltwater samples of the North Florida Peninsula region and Southeastern Tunisia are selected to represent groundwater. The results show that the divalent ions have contributed 78.78% and 60.89% to the total charge flux for the investigated groundwater. Besides, the divalent ions require half energy per unit charge flux compared to monovalent ions under the same activity ratio. The investigated groundwaters predict lower entropy generation rates than NaCl solution (e.g., by 39% at an applied potential of 90 mV). Moreover, a significant decrease in the entropy generation rates from 18% to 50% is observed for groundwater when compared with the case of NaCl solution due to the concentrate salinity variation from 1.25 to 1.75 times of diluate stream salinity.

Brackish water desalination can be performed efficiently using electrodialysis (ED). The technology can also be used to mitigate hypersalinity (>50,000 parts per million (ppm)). In this study, a simple and modified lumped ED model combined with cost calculations is used to perform a normalized sensitivity analysis up to 160,000 ppm. The model takes care of the effect of Donnan potential as well as boundary layers (films) and water transport through charged membranes. The analysis reveals that the (linear) velocity and feed concentration are generally the most significant factors affecting ED performance. Considering both control and cost issues, for the specific energy consumption per unit of salt removed, an optimal flow velocity should be chosen. For the rate of salt removal, a combination of lower flow velocity and optimal feed concentration is recommended. In the ED design case, the analysis shows that the feed concentration is generally the most significant factor. Considering both control and cost issues, for the total membrane area and rate of salt removal, a lower feed concentration is recommended irrespective of cost considerations.

In the present work, strength of momentum least mean square (MLMS) algorithm is exploited for nonlinear system identification problems represented with Hammerstein model. The MLMS algorithm uses the previous gradient information to estimate the current weights instead of using only current value of gradient; thus, it is faster in the convergence and less probable to trap in local minima. The perfection of the design scheme is certified through effective parameter estimation of nonlinear Hammerstein control autoregressive models. The robustness of the scheme is established by examining the performance for different levels of noise variance. The performance comparison through mean square error and Nash–Sutcliffe efficiency parameters, calculated for sufficiently large number of multiple runs, proves the intrinsic worth of MLMS algorithm in system identification.

In this paper, a normalized sensitivity analysis is done on an electrodialysis plant for various design and performance parameters. From the angle of design and performance, the most significant variables were the feed concentration and current efficiency, respectively. For the design aspect, plant size determination is affected less at higher feed salinities due to variations in the feed concentration, which seems to be favorable for high salinity applications. For the performance aspect, it is found that larger fluctuations in plant cost may occur while operating at higher feed concentrations. The desired diluate concentration and, thus, limiting current density as well as expected energy consumption may be more difficult to maintain at higher current efficiencies. Yet, the limiting current density is less sensitive at higher flow velocities. Therefore, the above problem could possibly be countered by using a combination of higher current efficiencies with higher flow velocities.

Maintenance plays a critical role in reducing operating cost and maximizing reliability of a complex engineering system. This paper proposes a novel maintenance-focused, system-level design framework that attempts to capture the interactions between maintenance strategies and system-level design parameters overlooked in current modeling approaches. The goal of this maintenance-focused approach is to help designers better understand the interconnectedness of system architecture, choice of maintenance strategy, and uncertainties in a design. Application of the proposed design framework is demonstrated through a case example of a power plant condenser system. Results show that using an integrated approach can reveal the many nonobvious interactions between subsystems, and produce system designs that have lower life-cycle cost compared to traditional sequential design approaches.

In this paper, the result of an experimental study on thermal performance of different metal foam heat sinks is presented and compared with conventional solid heat sink. Experiments were performed on aluminum metal foams having 93% porosity with pore density of 4 and 8 PPI (i.e. pores per inch). The forced convection results show that heat sink with thermal spray coating outperforms a thermally glued sample with up to 9.8% more temperature drop under same operating test conditions. Air flow speed variations reveal that heat transfer rate changes significantly with the variation of air speed. Further studies with multiple fin samples show that 45° is the best orientation between the heat sink and the flow for maximum heat dissipation. For a single fin, the best orientation is 90°. Results show that power dissipation at a fixed fin base temperature is an appropriate metrics for comparing thermal performance of metal foam heatsinks.

In this work, a prediction equation is proposed that determines performance parameters of fouled power systems as long as heat transfer in the two-phase region is dominant. Fouling was simulated by degrading the overall conductance. Dimensional analysis was used to reduce the problem to seven Pi groups. Since behavior found in endoreversible systems is often imitated by real systems, the endoreversible case was used for initial demonstration followed by a simulated Rankine cycle. Using an example problem, during degradation of the overall conductance, the observed parameters were found to behave logarithmically. Prediction was done by combining data under specified conditions for finite thermal capacitances. This type of model can offer benefit through saving both money and time by decreasing required number of experiments and/or simulations as well as in planning better cleaning schedules.

In this paper, a seawater reverse osmosis desalination plant with various energy recovery systems is studied using exergy analysis. These energy recovery devices include turbines and pressure exchangers as well as infinite area based single and two-stage pressure retarded osmosis units. The appropriate exergetic efficiency definition for such systems is mentioned. The effect of pump and turbine efficiency, salinity, temperature and mass ratio is studied using a validated program. In this regard, modified Van't Hoff constants for a large range of seawater surface temperatures are also determined. The best efficiency was obtained using the pressure exchanger for all systems investigated. Use of pressure retarded osmosis units as energy recovery devices provided efficiencies nearly equal to or less than the hydro-turbine. Thus, for the range investigated, it does not seem to be a viable energy recovery method for reverse osmosis units with seawater feed since constraints such as concentration polarization and finite area would further decrease performance.