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Thermal design and analysis of heat exchangers are predominantly conducted considering constant heat transfer coefficients. However, these vary along the length and affect the calculations of heat transfer rates and area allocations. The current paper investigates the variations in the heat transfer coefficients in plate heat exchangers (PHX), using different numerical approaches. The heat transfer coefficient is calculated at the inlet, outlet, and systematically selected intermediate points for each method. The analysis is conducted for two different systems, i.e., a laboratory-scale and an industrial scale PHX at different chevron angles. It is concluded that the effect of the variable heat transfer coefficient is more significant for the large-scale heat exchanger due to high flow rates, geometrical specifications, Reynolds number, and thermophysical properties. The deviation of the local heat transfer coefficient along the heat exchanger length is approximately 9–14% and 3–6% for industrial and laboratory scale PHX, while an area deviation of around 15% is observed.

Speaker diarization system identifies the speaker homogenous regions in those set of recordings where multiple speakers are present. It answers the question ‘who spoke when?’. The data set for speaker diarization usually consists of telephone, meetings, TV/ talk shows, broadcast news and other multi-speaker recordings. In this paper, we present the performance of our proposed multimodal speaker diarization system under noisy conditions. Two types of noises comprising additive white Gaussian noise (AWGN) and realistic environmental noise is used to evaluate the system. To mitigate the effect of noise, we propose to add an LSTM based speech enhancement block in our diarization pipeline. This block is trained on synthesized data set with more than 100 noise types to enhance the noisy speech. The enhanced speech is further used in multimodal speaker diarization system which utilizes a pre-trained audio-visual synchronization model to find the active speaker. High confidence active speaker segments are then used to train the speaker specific clusters on the enhanced speech. A subset of AMI corpus consisting of 5.4 h of recordings is used in this analysis. For AWGN, the LSTM model performance improvement is comparable with Wiener filter while in case of realistic environmental noise, the LSTM model improves significantly as compared to Wiener filter in terms of diarization error rate (DER).

Exergoeconomic analysis, a simultaneous investigation of exergetic and monetary performance has attained significant attention to analyze and improve the performance of energy conversion systems. This combined analysis allows an individual audit of all the components in the system. The research is particularly useful for multi-component systems to get a better understanding of how effectively each component consumes energy and economic capital. This chapter aims to present a comprehensive theoretical framework for exergoeconomic study of thermal systems. For this purpose, the framework is initially developed for standalone heat exchangers and then extended to commercial-scale thermal desalination systems consisting of preheaters, pumps, evaporators, and compressors, etc. The exergetic and economic values of each stream in the system were evaluated using the developed framework. The sensitivity and parametric analysis of different thermodynamic and economic parameters on the system performance was conducted to study the performance variations. The presented model can be generalized for performance analysis of other systems.

The performance of photovoltaic modules is adversely affected by an increase in photovoltaic cell temperature. Cooling of panels may lead to temperature non-uniformity in the photovoltaic panel, thus limiting the maximum efficiency of the cooled photovoltaic panel. In the current work, the design of a novel heat exchanger that can be used for uniform cooling of photovoltaic modules is presented. For this purpose, a computational fluid dynamics model has been set up. Using the model, the effects of various heat exchanger design parameters (like channel numbers, manifold width, the location of inlet/exit ports, and tapered channels) on its performance are sequentially analyzed resulting in fourteen designs. The performance is quantified by three parameters: top surface average temperature, temperature non-uniformity for photovoltaic module cooling quality, and the heat transfer per unit pumping power. The resulting optimized design is found to be a novel V-shaped heat exchanger design for the photovoltaic module cooling. It has a lower average temperature and temperature non-uniformity, smaller hotspots, and lower pumping power. The optimal design is further examined using experimental particle image velocimetry measurements.

The trend of applying mathematical foundations of fractional calculus to solve problems arising in nonlinear sciences, is an emerging area of research with growing interest especially in communication, signal analysis and control. In the present study, normalized fractional adaptive strategies are exploited for automatic tuning of the step size parameter in nonlinear system identification based on Hammerstein model. The brilliance of the methodology is verified by mean of viable estimation of electrically stimulated muscle model used in rehabilitation of paralyzed muscles. The dominance of the schemes is established by comparing the results with standard counterparts in case of different noise levels and fractional order variations. The results of the statistical analyses for sufficient independent runs in terms of Nash-Sutcliffe efficiency, variance account for and mean square error metrics validated the consistent accuracy and reliability of the proposed methods. The proposed exploitation of fractional calculus concepts makes a firm branch of nonlinear investigation in arbitrary order gradient-based optimization schemes.

While representing a class of signals in term of sparsifying transform, it is better to use a adapted learned dictionary instead of using a predefined dictionary as proposed in the recent literature. With this improved method, one can represent the sparsest representation for the given set of signals. In order to ease the approximation, atoms of the learned dictionary can further be grouped together to make blocks inside the dictionary that act as a union of small number of subspaces. The block structure of a dictionary can be learned by exploiting the latent structure of the desired signals. Such type of block dictionary leads to block sparse representation of the given signals which can be good for reconstruction of the medical images. In this article, we suggest a framework for MRI reconstruction based upon block sparsifying transform (dictionary). Our technique develops automatic detection of underlying block structure of MR images given maximum block sizes. This is done by iteratively alternating between updating the block structure of the sparsifying transform (dictionary) and block-sparse representation of the MR images. Empirically it is shown that block-sparse representation performs better for recovery of the given MR image with minimum errors.

To promote online businesses and sales, e-commerce industry focuses to fulfill users' demands by giving them top set of recommendations which are ranked through different ranking measures.Deep learning based auto-encoder models have further improved the performance of recommender systems. A state-of-the-art collaborative denoising auto-encoder (CDAE) models user-item interactions as a corrupted version of users rating inputs. However, this architecture still lacks users' ratings-trend information which is an important parameter to recommend top-N items to users. In this paper, building upon CDAE characteristics, we propose a novel users rating-trend based collaborative denoising auto-encoder (UT-CDAE) which determines user-item correlations by evaluating rating-trend(High or Low) of a user towards a set of items. This inclusion of a user's rating-trend provides additional regularization flexibility which helps to predict improved top-N recommendations. The correctness of the suggested method is verified through different ranking evaluation metrics i.e., (mean reciprocal rank, mean average precision and normalized discounted gain), for various input corruption values, learning rates and regularization parameters.Experiments on standard ML-100K and ML-1M datasets show that suggested model has improved performance overstate-of-the-art denoising auto-encodermodels.

The demand for recommender systems in E-commerce industry has increased tremendously. Efficient recommender systems are being proposed by different E-business companies with the intention to give users accurate and most relevant recommendation of products from huge amount of information. To improve the performance of recommender systems, various stochastic variants of gradient descent based algorithms have been reported. The scalability requirement of recommender systems needs algorithms with fast convergence to generate recommendations of specific items. Using the concepts of fractional calculus, an efficient variant of the stochastic gradient descent (SGD) was developed for fast convergence. Such fractional SGD (F-SGD) is further accelerated by adding a momentum term, thus termed as momentum fractional stochastic gradient descent (mF-SGD). The proposed mF-SGD method is shown to offer improved estimation accuracy and convergence rate, as compared to F-SGD and standard momentum SGD for different proportions of previous gradients, fractional orders, learning rates and number of features.

In this work, the fabrication and characterization of a dual-purpose membrane is reported: (i) oil-water separation with high efficiency, and (ii) effective and rapid photocatalytic degradation of hazardous environmental pollutants. Nanoparticles of a rare-earth oxide, cerium (IV) oxide, synthesized by a simple co-precipitation technique, were spray-coated onto stainless steel membranes to obtain a uniform coating with superwetting characteristics. The as-synthesized cerium (IV) oxide nanoparticles and its spray-coated stainless steel membrane were characterized by advanced analytical techniques. X-ray diffraction, selected area electron diffraction, and electron microscopy results of the cerium oxide particles showed a high degree of crystallinity and uniform particle size of ∼50 nm. Elemental surface analysis using X-ray photoelectron spectroscopy showed the characteristic peaks for Ce4+, thereby confirming the presence of cerium oxide nanoparticles. Contact angle measurements showed the coated membranes to be superhydrophobic (∼150°) and superoleophilic (∼0°). When used in a simple laboratory setup, the membranes were able to separate oil and water with a high efficiency (∼99%). Furthermore, the coated membrane showed enhanced photocatalytic activity under UV light irradiation resulting in the rapid degradation of organic persistent pollutants like MB dye in water. To summarize, this work presents an innovative approach in the application of multifunctional membranes for effective water treatment.

Integration of energy recovery section with thermal desalination systems improves their performance from thermodynamics, economics, and environmental viewpoints. This is because it significantly reduces input energy, heat transfer area, and capital cost requirements. Above all, the system outlet streams can achieve thermal equilibrium with the environment by supplying heat for useful preheating purposes thus reducing the environmental impacts. The plate heat exchangers are generally employed for this purpose as preheaters. The current paper presents a comprehensive investigation and optimization of these heat exchangers for thermal desalination systems applications. An experimentally validated numerical model employing Normalized Sensitivity Analysis and Genetic Algorithm based cost optimization is developed to investigate their performance at assorted operating conditions. The analysis showed that the heat transfer coefficient, pressure drop, and outlet water cost were improved by an increase in feed flow rate. However, with an increased flow rate, the comprehensive output parameter (h/ΔP) decreased due to the high degree increase in pressure drop. Moreover, an increase in the chevron angle reduced the heat transfer coefficient, pressure drop, and water cost. Finally, the optimization lowered the heat transfer area by ~79.5%, capital investment by ~62%, and the outlet cost of the cold stream by ~15.7%. The operational cost is increased due to the increased pressure drop but the overall impact is beneficial as Ctotal of equipment is reduced by ~52.7%.

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).

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.

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.

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.

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.

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.

The paper presents an economic optimization of a STHX with two commonly adopted (i.e., Kern and Bell-Delaware) and one rarely explored (i.e., Wills-Johnston) methods. A detailed numerical code concerning thermal, hydraulic, exergy, and economic analysis of STHX is developed for all three methods. Normalized sensitivity analysis, parametric study, and Genetic Algorithm are used to ascertain the most influential parameters and optimize the total cost. It is observed that the calculations made using the Wills-Johnston method were reasonably close to the Bell-Delaware method. While the Kern method showed a significant deviation in the shell side calculations because of the several assumptions in this method. The parametric analysis showed that increasing the mass flow rate and the number of baffles increased the operating cost because of an exponential increase in the pressure drops. Finally, the optimization reduced the heat transfer area by ~26.4%, capital cost by ~20%, operational cost by ~50%, total cost by ~22%, and the stream cost by ~21%.

Highlights • A full treatment for thermoeconmic analysis of desalination systems is presented. • A detailed review is conducted to highlight the correlations of important economic parameters. • A discussion on cost balance equations for important desalination components is presented. • A sample model is developed for mechanical vapor compression desalination systems. • The monetary value of each stream is calculated using relevant fiscal parameters., Thermoeconomic analysis, a combined application of thermodynamic and economic analyses, has emerged as an important tool to optimize the performance of desalination systems. Contrary to conventional economic analysis, it offers flexibility to investigate and improve the performance of each component in the system, individually. The current paper presents a comprehensive framework for conducting thermoeconomic analysis of desalination systems. In this regard, different energy calculation methods are discussed first. Then a detailed review of theoretical developments of thermoeconomic analyses is conducted to summarize the correlations/magnitude of important economic parameters. This is followed by a discussion on cost balance equations for important desalination components. Finally, a systematic thermoeconomic analysis model is developed for the mechanical vapor compression desalination system operating under different arrangements as an example. The monetary value of each stream calculated using appropriate fiscal parameters in the system is presented in the form of a cost flow diagram. The study can be used to conduct the thermoeconomic analysis of other commercial desalination systems.

This paper introduces and evaluates an innovative humidification-dehumidification (HDH) desalination system integrated with a double-effect absorption refrigeration system to produce an abundant amount of freshwater and to provide a cooling effect for air conditioning purposes. The seawater stream of HDH system is used to cool condenser and absorber of the absorption refrigeration system while attaining a sufficient heat to drive the HDH system. The influence of operating conditions on the integrated system performance is investigated. The performance indices are selected to be: gained output ratio (GOR), coefficient of performance (COP), energy performance, freshwater production, and freshwater cost. The system can produce freshwater of 1145 L/h and a cooling capacity of 62.45 TR. The optimal performance indices are found to be 4.54 for GOR, 1.29 for COP, and 5.83 for energy performance. Furthermore, without accounting for the cooling effect, the freshwater cost is estimated to be 2.89 $/m3. In addition to the air conditioning capability, the integrated system performance shows an enhancement of 2.20 times for GOR, 2.21 times for freshwater production, and 8.24 times for water cost reduction over the traditional HDH system.

Resistance to fouling is often cited as an advantage of emerging desalination technologies such as forward osmosis and membrane distillation over the widely-used reverse osmosis process. However, the nature and magnitude of differences in fouling behavior between these three processes are not well characterized. This study directly compares the fouling and scaling behavior of reverse osmosis (RO), forward osmosis (FO), and direct contact membrane distillation (MD) in the same membrane module under identical hydrodynamic conditions (flux and cross-flow velocity). Fouling experiments were conducted using calcium sulfate as a model inorganic foulant and alginate as a model organic foulant. Although all three processes tolerated some degree of feed supersaturation for 36 h without inorganic fouling (scaling), FO exhibited the greatest scaling resistance, withstanding a feed of 33 ± 2 mM CaSO₄ (approximately twice saturation) without significant flux decline. Scaling occurred at similar concentrations at the membrane between MD and RO; however, while MD tolerated a more concentrated bulk feed due to reduced concentration polarization, flux decline after fouling was considerably more severe in MD. In contrast, MD tolerated organic fouling much better than FO or RO: despite accumulating a similar quantity of alginate gel over 18 h of operation, flux declined only 14% in MD versus 46–47% in RO and FO. These results are explained with respect to differences in temperature, membrane materials, and transport mechanisms between the three processes. Although FO and MD each exhibited superior resistance to one type of foulant, neither process outperformed RO in resistance to both organic and inorganic fouling. These findings inform a more nuanced approach to process selection for the treatment of complex water sources. Keywords: Desalination; Forward osmosis; Fouling resistance; Membrane distillation; Reverse osmosis

We propose the use of electrodialysis to desalinate produced waters from shale formations in order to facilitate water reuse in subsequent hydraulic fracturing processes. We focus on establishing the energy and equipment size required for the desalination of feed waters containing total dissolved solids of up to 192,000 ppm, and we do this by experimentally replicating the performance of a 10-stage electrodialysis system. We find that energy requirements are similar to current vapour compression desalination processes for feedwaters ranging between roughly 40,000-90,000 ppm TDS, but we project water costs to potentially be lower. We also find that the cost per unit salt removed is significantly lower when removed from a high salinity stream as opposed to a low salinity stream, pointing towards the potential of ED to operate as a partial desalination process for high salinity waters. We then develop a numerical model for the system, validate it against experimental results and use this model to minimise salt removal costs by optimising the stack voltage. We find that the higher the salinity of the water from which salt is removed the smaller should be the ratio of the electrical current to its limiting value. We conclude, on the basis of energy and equipment costs, that electrodialysis processes are potentially feasible for the desalination of high salinity waters but require further investigation of robustness to fouling under field conditions., Massachusetts Institute of Technology. Office of the Dean for Graduate Education (Hugh Hampton Young Memorial Fellowship), MIT Energy Initiative

A significant barrier to further use of hydraulic fracturing to recover shale oil and/or gas is the treatment and/or disposal of hypersaline produced water. This work is an analysis of produced water from Nova Scotia, with the aim of understanding how scale impacts the choice of desalination system used in its treatment. Four water samples are presented, and for a representative case, the supersaturation of some likely scalants is estimated as a function of temperature, recovery ratio, and pH. This supersaturation map is then compared to conditions representative of common desalination systems, allowing the identification of limitations imposed by the water's composition. In contrast to many natural waters, it is found that sodium chloride is the most likely first solid to form at high recovery ratios, and that the top temperature of thermal desalination systems is unlikely to be scale-limited in the treatment of these waters., Center for Clean Water and Clean Energy at MIT and KFUPM (Project R4-CW-08)

A cost analysis reveals that hybridisation of electrodialysis with reverse osmosis is only justified if the cost of water from the reverse osmosis unit is less than 40% of that from a stand-alone electrodialysis system. In such cases the additional reverse osmosis costs justify the electrodialysis cost savings brought about by shifting salt removal to higher salinity, where current densities are higher and equipment costs lower. Furthermore, the analysis suggests that a simple hybrid configuration is more cost effective than a recirculated hybrid, a simple hybrid being one where the reverse osmosis concentrate is fed to the electrodialysis stack and the products from both units are blended, and a recirculated being one hybrid involving recirculation of the electrodialysis product back to the reverse osmosis unit. The underlying rationale is that simple hybridisation shifts salt removal away from the lowest salinity zone of operation, where salt removal is most expensive. Further shifts in the salinity at which salt is removed, brought about by recirculation, do not justify the associated increased costs of reverse osmosis., Hugh Hampton Young Memorial Fellowship, Center for Clean Water and Clean Energy at MIT and KFUPM (Project R15-CW-11)

In many forward osmosis applications, flux is maximised (and capital costs minimised) when the membrane is oriented such that the feed solution faces the support layer (PRO mode). Here, a framework is developed to understand the factors that determine the membrane orientation that maximises flux. In the absence of fouling, a dimensionless form of the water transport equations reveals the importance of three dimensionless groups: the ratio of draw to feed osmotic pressure, the ratio of draw to feed solute diffusivity, and the resistance to water transport of the support layer relative to the active layer. A parametric study of these parameters and an application of the dimensionless equations to three important FO processes reveal that having the draw solution face the support layer (FO mode) can maximise flux in specific instances. Interestingly, this implies that operation in FO mode can both maximise flux and minimise fouling for fertigation applications and the concentration of flowback waters from hydraulic fracturing., Center for Clean Water and Clean Energy at MIT and KFUPM (Project R15-CW-11), United States. Dept. of State. Fulbright Science & Technology Program, International Desalination Association (Channabasappa Memorial Scholarship), MIT Martin Family Society of Fellows for Sustainability, Hugh Hampton Young Memorial Fellowship

Humidification dehumidification (HDH) is a promising technology for small-scale seawater desalination and has widespread application in drinking and industrial water treatment systems. This paper demonstrates the significance of a novel parameter known as the ‘modified heat capacity rate ratio’ (HCR) in the thermal design of HDH systems and in simultaneous heat and mass exchange (HME) devices. HCR is of particular importance in developing a fundamental understanding of the concept of thermodynamic balancing. A pilot-scale HDH unit (with a peak production capacity of 700 l/day) has been constructed and detailed experiments have been performed on this unit. Based on these experiments, the recently developed theories behind the design of HDH systems with or without mass extraction and injection are validated. Furthermore, important concepts with regard to design and optimization of HME devices have been studied in the present experiments.

In this work, an experimental investigation into the effects, in terms of energy, of employing a dedicated mechanical subcooling cycle with a residential 1.5 ton simple vapor compression refrigeration system is presented. A comparative analysis of the experimental cycle performance is conducted with and without the dedicated subcooler cycle when the room temperature is kept between 18 and 22 °C. This is done in order to ascertain the percentage increase in efficiency due to use of a dedicated subcooling loop. R22 is employed as the refrigerant in the main cycle whereas R12 is flowing in the dedicated subcooling cycle. The experimental outcomes indicate that the load carrying capacity of the evaporator increased by approximately 0.5 kW when R22 was subcooled, in the main cycle, by 5–8 °C. It was also noted that, by using the subcooling, the second-law efficiency of the cycle increased by an average of 21%. Furthermore, the general trend indicated that this percentage increase is inversely proportional to the ambient temperature variation. The experimental work proves that dedicated subcooling can be used for increasing cooling capacity and efficiency.

In this paper, a novel thermodynamic cycle is proposed, termed the reversed chemical engine cycle. In the cycle, a net input of work is used to transfer mass from a low chemical potential reservoir to a high chemical potential reservoir. The cycle has two mass exchangers, a pump and a turbine. The only irreversibility considered in the model is finite-rate mass transfer. Similar to the reversed Carnot cycle, expressions for the performance ratio (analogous to the coefficient of performance) are obtained under the condition of minimized power requirement for the endoreversible and, in turn, the reversible case. The reversed mass engine cycle is shown to be a special case of the reversed chemical engine. An equipartitioned hybrid forward osmosis reverse osmosis (FO–RO) system is considered as an example of the cycle., King Fahd University of Petroleum & Minerals (Project Number R15-CW-11)

Estimating the harmonic parameters is fundamental requirement for signal modelling in a power supply system. In this study, exploration and exploitation in fractional adaptive signal processing (FrASP) is carried out for identification of parameters in power signals. We design FrASP algorithms based on recently introduced variants of generalized least mean square (LMS) adaptive strategies for parameter estimation of the model. The performance of the proposed fractional adaptive schemes is evaluated for number of scenarios based on step size and noise variations. Results of the simulated system for sufficient large number of independent runs validated the reliability and effectiveness of the given methods through different performance measures in terms of mean square error, variance account for, and Nash Sutcliffe efficiency.

The central chilled water system servicing one of the academic buildings in King Fahd University of Petroleum & Minerals (KFUPM) campus located in Dhahran is numerically modeled in detail with a special focus on the pumping scheme. The software Engineering Equation Solver (EES) is used for the modeling and simulation of the system. The bin data along with the weather profile is utilized to calculate the annual energy consumption of the system for three cities in Saudi Arabia. It is found for Dhahran that by replacing the existing single loop constant pumping scheme by the constant primary and variable secondary scheme, an 8% saving in the total annual energy consumption is achieved, which is increased to 13% by adopting the single loop variable primary scheme. Similarly, for the climatic conditions of Riyadh and Jeddah reductions in annual energy consumption by approximately 7% are obtained by adopting the constant primary and variable secondary scheme. However, if the single loop variable pumping scheme is adopted, the energy savings for Riyadh and Jeddah increases to 12% and 11%, respectively.

Performance characteristics due to fouling in a vapor compression cycle with integrated mechanical sub-cooling are investigated for various applications. Considering the first set of refrigerants i.e. R134a, R410A and R407C, from a first law standpoint, the COP indicates that R134a always performs better unless only the evaporator is being fouled. From a second law standpoint, the second-law efficiency indicates that R134a performs the best in all cases. Considering the second set of refrigerants i.e. R717, R404A and R290, the COP indicates that R717 always performs better unless only the evaporator is being fouled; however, the second-law efficiency indicates that R717 performs the best in all cases. Furthermore, the performance degradation due to fouling of the evaporator always has a larger effect on cooling load capacity while the performance degradation of the condenser always has an overall larger effect on the sub-cooler compressor power requirement as well as the COP of the system. In light of the data generated, a new performance degradation law, presented earlier, is shown to be applicable for this system as well that can reduce the amount of experimentation and help predict relevant quantities of the refrigeration system.

Exergy analysis is a powerful diagnostic tool in thermal systems performance evaluation. The use of such an analysis in seawater desalination processes is of growing importance to determine the sites of the highest irreversible losses. In the literature, exergy analyses of seawater desalination systems have sometimes modeled seawater as sodium chloride solutions of equivalent salt content or salinity; however, such matching does not bring all important properties of the two solutions into agreement. Furthermore, a common model that represents seawater as an ideal mixture of liquid water and solid sodium chloride may have serious shortcomings. Therefore, in this paper, the most up-to-date thermodynamic properties of seawater, as needed to conduct an exergy analysis, are given as correlations and tabulated data. The effect of the system properties as well as the environment dead state on the exergy and flow exergy variation is investigated. In addition, an exergy analysis for a large MSF distillation plant is performed using plant operating data and results previously published using the above-mentioned ideal mixture model. It is demonstrated that this ideal mixture model gives flow exergy values that are far from the correct ones. Moreover, the second law efficiency differs by about 80% for some cases., Center for Clean Water and Clean Energy at MIT and KFUPM

The performance of a solar still is predicted though an improved and updated mathematical model. The model is based on classical energy balance equations; however, variable properties were considered in addition to a more reliable correlation for convection heat transfer from the seawater surface and the still glass cover. The effect of density variation within the solar still due to water vapor concentration difference is taken into consideration through a modified expression of the temperature difference (ΔT') and a more reliable expression for the heat transfer coefficient within the still that was developed for tilted covers. The performance of the still is validated against the published experimental values. In addition, the (distillate) productivity was reported for two days that represent both summer and winter conditions in Dhahran, Saudi Arabia. A parametric study was performed to identify the effect of the most influential parameters on the still performance. In addition, a sensitivity analysis ...

This paper applies irreversibility analysis to characterize humidification-dehumidification (HD) desalination cycles and to identify how to further improve cycles and components. It is shown that minimizing specific entropy generation of the cycle maximizes the gained output ratio (GOR). It is also shown that each cycle has one limiting component that cannot be substantially improved and a second component that should be the target of efforts to minimize entropy generation. Finally, the failure of exergy analysis to yield conclusive results for on-design HD cycle analysis is discussed briefly., Center for Clean Water and Clean Energy at MIT and KFUPM

World-wide water scarcity, especially in the developing world, indicates a pressing need to develop inexpensive, decentralized small-scale desalination technologies which use renewable resources of energy. This paper provides a comprehensive review of the stateof- the-art in one of the most promising of these technologies, solar-driven humidification-dehumidification (HDH) desalination. Previous studies have investigated many different variations on the HDH cycle. In this paper, performance parameters which enable comparison of the various versions of the HDH cycle have been defined and evaluated. To better compare these cycles, each has been represented in psychometric coordinates. The principal components of the HDH system are also reviewed and compared, including the humidifier, solar heaters, and dehumidifiers. Particular attention is given to solar air heaters, for which design data is limited; and direct air heating is compared to direct water heating in the cycle assessments. Alternative processes based on the HDH concept are also reviewed and compared. Further, novel proposals for improvement of the HDH cycle are outlined. It is concluded that HDH technology has great promise for decentralized small-scale water production applications, although additional research and development is needed for improving system efficiency and reducing capital cost., King Fahd University of Petroleum and Minerals

http://www.deswater.com/vol16.php, Correlations and data for the thermophysical properties of seawater are reviewed. Properties examined include density, specific heat capacity, thermal conductivity, dynamic viscosity, surface tension, vapor pressure, boiling point elevation, latent heat of vaporization, specific enthalpy, specific entropy and osmotic coefficient. These properties include those needed for design of thermal and membrane desalination processes. Results are presented in terms of regression equations as functions of temperature and salinity. The available correlations for each property are summarized with their range of validity and accuracy. Best-fi tted new correlations are obtained from available data for density, dynamic viscosity, surface tension, boiling point elevation, specific enthalpy, specific entropy and osmotic coefficient after appropriate conversion of temperature and salinity scales to the most recent standards. In addition, a model for latent heat of vaporization is suggested. Comparisons are carried out among these correlations, and recommendations are provided for each property, particularly over the ranges of temperature and salinity common in thermal and/or reverse osmosis seawater desalination applications., King Fahd University of Petroleum and Minerals, Center for Clean Water and Clean Energy at MIT and KFUPM

Humidification–dehumidification desalination (HDH) is a promising technology for small-scale water production applications. There are several embodiments of this technology which have been investigated by researchers around the world. However, from a previous literature [1], we have found that no study carried out a detailed thermodynamic analysis in order to improve and/ or optimize the system performance. In this paper, we analyze the thermodynamic performance of various HDH cycles by way of a theoretical cycle analysis. In addition, we propose novel high performance variations on those cycles. These high-performance cycles include multi-extraction, multi-pressure and thermal vapor compression cycles. It is predicted that the systems based on these novel cycles will have gained output ratio in excess of 5 and will outperform existing HDH systems., King Fahd University of Petroleum and Minerals, Center for Clean Water and Clean Energy at MIT and KFUPM

An analysis was carried out to study the performance of spine fins of different configurations when subjected to simultaneous heat and mass transfer mechanisms. The temperature and humidity ratio differences are the driving forces for the heat and mass transfer, respectively. Analytical solutions are obtained for the efficiency and temperature distribution over the spine surface when the surface condition is fully wet. A correction chart is developed to correct the value of the dry fin parameter if the fin surface condition is fully wet. The effect of atmospheric pressure on the spine efficiency was also studied as well as the spine optimum geometries were obtained such that a maximum amount of heat transfer rate occurs. It is shown that the closed-form solution for a dry spine case discussed in text books is a special case for the solutions presented in this paper.

In this paper, we present thermodynamic analysis of counter flow wet cooling towers and evaporative heat exchangers using both the first and second laws of thermodynamics. A parametric study is carried out to determine the variation of second-law efficiency as well as exergy destruction as a function of various input parameters such as inlet wet bulb temperature. Irreversible losses are determined by applying an exergy balance on each of the systems investigated. In this regard, an engineering equation solver (EES) program, with built-in functions for most thermodynamic and transport properties, is used. The concept of total exergy as the sum of thermomechanical and chemical parts is employed in calculating the flow exergies for air and water vapor mixtures. For the different input variables investigated, efficiencies were, almost always, seen to increase or decrease monotonically. We notice that an increase in the inlet wet bulb temperature invariably increases the second-law efficiency of all the heat exchangers. Also, it is shown that Bejan's definition of second-law efficiency is not limited in evaluating performance. Furthermore, it is understood that the variation in the dead state does not significantly affect the overall efficiency of the system.

Humidification dehumidification (HDH) is a desalination technology that has shown promise in small scale, decentralized applications. Previous studies on the multi-staging of HDH have used fixed-effectiveness models which do not explicitly account for transport processes in the components. However, to fully understand the effect of the variation of the mass flow rate ratio, it is necessary to implement heat and mass transfer models of the HDH system. In this paper, we model an HDH system consisting of a packed-bed humidifier and a multi-tray bubble column dehumidifier. We study the effect of the mass flow rate ratio on the performance of a fixed-size system, and we consider its effect on the entropy generation and the driving forces for heat and mass transfer. In addition, we define a generalized energy effectiveness for heat and mass exchangers. We also implement an air extraction/injection and simulate a wide range of operating conditions. We define criteria for the best system performance, and we study the effect of the distribution of available area between separate stages. We also present a thorough explanation of why the direction of extraction should always be from the humidifier to the dehumidifier., Center for Clean Water and Clean Energy at MIT and KFUPM (Project R4-CW-08)

In this paper we deal with the effects of varying reference temperature on the exergy efficiencies of one- and two-stage crude oil distillation units. Such units essentially consist of the crude oil heating furnace, the distillation column and a network of heat exchangers. Since the exergy efficiency is a key parameter to see how well the system is performing, we undertake a study on the influence of the reference temperature on such efficiencies. In this regard, a commercial software package, SimSci/PRO II program is used for the calculations. The results show that increasing reference temperature decreases the exergy efficiency in both one- and two-stage crude oil distillation systems and also increases the difference between the exergy efficiencies of both systems. Therefore, the exergy losses increase in the crude oil distillation systems.

We have had several conversations with Knutson during recent months, and we certainly agree that the one-dimensional mass exchanger model is more appropriate than the zero-dimensional model which has appeared in much of the past literature and which we also applied. We have been working on revisions of these calculations that incorporate the one-dimensional model, and we report some of our findings in Refs. [2] ; [5]. However, we believe that PRO has clear potential for energy recovery, as we explain in detail below. Further, Knutson's analysis of the power generation is flawed and his conclusions regarding energy recovery are not accurate. Knutson's method of analysis makes the assumption of infinite membrane water permeability (equivalent to infinite surface area), taking the value of A in Eq. (1) to be infinity. Because the value of A for the membrane is assumed to be infinite, the local water flux is equal to zero at the inlet, outlet, or both ends of the PRO module. In another words, the driving force for the water flux will vanish at the inlet, outlet, or both ends. This is similar to the assumption of zero pinch at the end of a heat exchanger, such as might be obtained with infinite surface area. This is an interesting method, and it should give similar trends as given in Ref. [4] if it is applied correctly.

Large-scale desalination plants are complex systems with many inter-disciplinary interactions and different levels of sub-system hierarchy. Advanced complex systems design tools have been shown to have a positive impact on design in aerospace and automotive, but have generally not been used in the design of water systems. This work presents a multi-disciplinary design optimization approach to desalination system design to minimize the total water production cost of a 30,000m3/day capacity reverse osmosis plant situated in the Middle East, with a focus on comparing monolithic with distributed optimization architectures. A hierarchical multi-disciplinary model is constructed to capture the entire system’s functional components and subsystem interactions. Three different multi-disciplinary design optimization (MDO) architectures are then compared to find the optimal plant design that minimizes total water cost. The architectures include the monolithic architecture multidisciplinary feasible (MDF), individual disciplinary feasible (IDF) and the distributed architecture analytical target cascading (ATC). The results demonstrate that an MDF architecture was the most efficient for finding the optimal design, while a distributed MDO approach such as analytical target cascading is also a suitable approach for optimal design of desalination plants, but optimization performance may depend on initial conditions.Copyright © 2014 by ASME

We provide a thermoeconomic assessment of electrodialysis indicating that the technology is most productive and efficient for the partial desalination of feed streams at the higher end of the brackish range of salinities. After optimising the current density to minimise the sum of energy and equipment costs, we demonstrate that at low feed salinities the productivity, and hence equipment costs, of electrodialysis are hampered by the limiting current density. By contrast, at higher feed salinities both productivity and efficiency are hampered by the reduced chemical potential difference of salt in the diluate (low salinity) and concentrate (high salinity) streams. This analysis indicates the promise of further developing electrodialysis for the treatment of waters from oil, gas and coal-bed methane as well as flue-gas de-sulphurisation, where the partial desalination of streams at the high-end of the brackish range can be beneficial., Center for Clean Water and Clean Energy at MIT and KFUPM (Project R15-CW-11), United States. Dept. of State (International Fulbright Science & Technology Award), International Desalination Association (Channabasappa Memorial Scholarship), MIT Martin Family Society of Fellows for Sustainability, Hugh Hampton Young Memorial Fellowship

The demand is rising for desalination technologies to treat highly saline brines arising from hydraulic fracturing processes and inland desalination. Interest is growing in the use of electrical desalination technologies for this application. The hybridization of electrodialysis (ED) with reverse osmosis (RO) allows high salinities (beyond the range of RO alone) to be reached while avoiding the operation of ED with a low conductivity diluate stream. Such hybrid systems have been experimentally investigated for concentrates from brackish and seawater desalination. However, progress is required in the modelling and optimization of hybrid systems at higher concentrations. A novel hybrid arrangement of counterflow ED systems with reverse osmosis is presented to concentrate a saline feed at 120 ppt. The system is considered from the perspective of efficiency, membrane productivity and the levelised cost of water, with emphasis on the optimisation of current density. In contrast to brackish ED systems, membrane resistances are found to dominate diluate and concentrate resistances at high salinity. The current density found to minimise LCW (levelised cost of water) is significantly greater than the current density found to maximise efficiency, indicating the high current capital cost of ED per unit membrane area and poor membrane transport properties relative to RO. Finally, performance at high recoveries is found to be limited by high stream-to-stream concentration differences, increasing water transport via osmosis, decreasing efficiency and increasing the LCW., Fulbright Program, Martin Family Society of Fellows for Sustainability, International Desalination Association (Channabasappa Memorial Scholarship)