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Humidification dehumidification water desalination system using two cycles of air flow (open and closed-air cycles).

In this article, the optimal design of a novel multi-generation system for the production of electricity, cooling, heat and freshwater is discussed. In this system, a Proton exchange membrane fuel cell (PEM FC) is used to generate electricity, and the heat produced by it is absorbed by the Ejector Refrigeration Cycle (ERC) and used to provide cooling and heating capacity. A reverse osmosis (RO) desalination system is also used to supply freshwater. The esign variables in this research are operating temperature and pressure and current density of FC, as well as the operating pressure of the HRVG, evaporator, and condenser of the ERC system. In order to optimize the considered system, the exergy efficiency and total cost rate (TCR) of the system are considered as optimization objective functions. To this end, the genetic algorithm (GA) is used and the Pareto front is extracted. Also, three refrigerants R134a, R600 and R123 areused as ERC system refrigerant and their performance are evaluated. Finally, the optimal design point is selected. At the mentioned point, the exergy efficiency is 70.2% and the TCR of the system is 1.78 S/h.

Abstract Rice straw was subjected to fungal pretreatment using Pleurotus ostreatus and Trichoderma reesei to improve its biodegradability and methane production via solid-state anaerobic digestion (SS-AD). Effects of moisture content (65%, 75% and 85%), and incubation time (10, 20 and 30 d) on lignin, cellulose, and hemicellulose degradation during fungal pretreatment and methane yield during anaerobic digestion were assessed via comparison to untreated rice straw. Pretreatment with P. ostreatus was most effective at 75% moisture content and 20 d incubation resulting in 33.4% lignin removal and a lignin/cellulose removal ratio (selectivity) of 4.2. In comparison Trichoderma reesei was most effective at 75% moisture content and 20 d incubation resulting in 23.6% lignin removal and a lignin/cellulose removal ratio (selectivity) of 2.88. The corresponding methane yields were 263 and 214 L/kg volatile solids (VS), which were 120% and 78.3% higher than for the untreated rice straw, respectively.

This paper investigates the effect of the physical location of the auxiliary source of energy in thermosyphon solar water heaters and shows that the performance of the system can be optimised with respect to the geometry of the system components. The investigation has been based on a domestic thermosyphon solar water heating system, which was simulated using the TRNSYS programme. The annual solar fraction of the system, at the weather and socioeconomic conditions of Cyprus, is, at best, approximately 77% with an in-tank auxiliary heater configuration and 86% with an external auxiliary heater. It is demonstrated that the arrangement with the external auxiliary unit has a higher collector efficiency and results in a higher annual solar fraction. In the case of in-tank auxiliary, the system performance increases with the height of the auxiliary position from the bottom of the storage tank; with the auxiliary at the bottom of the storage tank the annual solar fraction is approximately 59%, compared to 77% when the auxiliary is located at the top of the tank. The system performance also depends on the height of the collector return from the bottom of the tank.

Abstract The viscosity of extra-heavy oils including bitumen can be reduced significantly by adding solvent such as toluene to enhance extraction, production, and transportation. Thus, prediction of viscosity and/or rheology of bitumen-solvent mixtures has become necessary. More so, selecting a suitable rheological model for simulation of flow in porous media has an important role to play in engineering design of production and processing systems. While several mixing rules have been applied to calculate the viscosity of bitumen-solvent mixtures, rheological model to describe the flow characteristics has rarely been published. Thus, in this investigation, rheological behavior of bitumen and bitumen-toluene mixtures (weight fractions of bitumen WB = 0, 0.25, 0.5, 0.6, 0.75, and 1 w/w) have been studied at the flow temperature (75 °C) of the bitumen and in the range of shear rates between 0.001 and 1000 s−1. The data were fitted using different rheological models including the Power law, Cross model, Carreau–Yasuda model, and the newly introduced ones herein named as Cross-Logistic and Logistic models. Then, a computational fluid dynamics (CFD) model was built using a scanning electron microscope (SEM) image of rock sample (representing a realistic porous geometry) to simulate pore scale flow characteristics. The observations revealed that the original bitumen exhibits a Newtonian behavior within the low shear rate region (0.001–10 s−1) and shows a non-Newtonian (pseudoplastic) behavior at the higher shear rate region (100–1000 s−1). Conversely, the bitumen-toluene mixtures show shear thinning (pseudoplastic) behavior at low shear rate region (0.001–0.01), which appears to become less significant within 0.01 to 0.1 s−1, and exhibit shear independent Newtonian behavior within 0.1 and 1000 s−1 shear rates. Moreover, except for the original bitumen, statistical error analysis of prediction ability of the tested rheological models as well as the results from the pore scale flow parameters suggested that the Power law might not be suitable for predicting the flow characteristics of the bitumen–toluene mixtures compared to the other models.

Abstract The present work aimed to explore the optimized conditions of hydrothermal co-liquefaction (co-HTL) of the green seaweed “Enteromorpha clathrata (EN)” and the lignocellulosic agricultural waste “rice husk (RH)”. Separate hydrothermal liquefaction (HTL) of EN and RH showed bio-oil yields of 26.0% and 45.6%, respectively. However, co-HTL under optimized conditions showed significant increase in the bio-oil yield by 71.7% over that of EN, and insignificant difference with that of RH. Nevertheless, the conversion ratio of co-HTL showed 10.6% significant increase over that of RH. GC-MS results showed that main compounds of EN and RH bio-oil lump into the C15–C20 and C5–C12 regions, mainly representing carbon range of diesel and gasoline, respectively. Short-chain (C5–C12) and long-chain (C14–C20) compounds in the bio-oil obtained by co-HTL represented 72% and 28%, respectively. In addition, the ratio of aromatic compounds in the bio-oil of RH was reduced by 9.3% as a result of co-HTL. In conclusion, results suggested 50% ethanol as a co-solvent, 300 °C and 45 min as optimum conditions for co-HTL of EN:RH (1:1 w/w). The present study demonstrated an efficient route for co-HTL of 3rd generation feedstocks with 2nd generation feedstocks which will have a significant impact on large-scale applications.

This work is a small effort in the production of an eco-friendly natural based antibacterial and anti-inflammatory finished cotton fabrics using the ethanolic extracts (Ex) of the sea grass Halophila stipulacea (H. stipulacea) and marine macroalgae [Colbomenia sinuosa (C. sinuosa) and Ulva fasciata (U. fasciata)]. The extracts were phytochemically screened for their constituents. These extracts were used to finish cotton fabrics by a variety of methods. Concerning this, fabrics (F) were singly treated with ethanolic extracts (ExF) of these marine organisms by the dip technique and the extract encapsulated with sodium alginate or meypro gum. The encapsulated fabric (EnF) was further finished individually with citric acid (CA), (EnF/CA) and mono-tert-butyl ether of glycerol (MTBG) binder (EnF/Bin) by the pad-dry-cure technique. The fabrics so-finished were evaluated for their antibacterial and anti-inflammatory activities without washing (control) and after different washing cycles. The results obtained showed that, both EnF/CA and EnF/Bin inhibit the bacterial growth by about 90% after 10 washing cycles for both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The anti-inflammatory activity, the potency% reached to 88.3% for the fabric encapsulated with microcapsules of sodium alginate/H. stipulacea sea grass and the EnF/CA.

Abstract This study focuses on improving the efficiency of the microwave (MW) pretreatment of waste activated sludge (WAS) through deflocculation mediated by sodium tripolyphosphate (STPP), a cationic binding agent. Deflocculated sludge was subjected to MW pretreatment to assess its impact on biomass disintegration. At the optimised energy for MW pretreatment (14,000 kJ/kg TS), the chemical oxygen demand (COD) solubilisation was 28% and 21% and the reduction in suspended solids (SS) was 38% and 26%, respectively, for deflocculated (treated with a cationic binding agent followed by microwaves) and flocculated (treated by microwaves alone) sludge samples. The formation of volatile fatty acids in the deflocculated sludge medium (840 mg/L) was comparatively higher than that in the flocculated sludge (420 mg/L) and the control (62 mg/L). This study indicates that deflocculated sludge is more amenable to hydrolysis. The results of a test of biochemical methane potential also confirmed the greater amenability of deflocculated sludge for anaerobic degradation.

Abstract Geological storage of Carbon Dioxide (CO2) can safely and permanently store a huge amount of anthropogenic greenhouse gases. However, the possible leakage of mobile gases through the cap rock that confines them within the reservoir is a cause of safety concerns. Residual and solubility trapping of the injected gas in the pores of the rock can reduce the amount of mobile gas lying below the cap rock. These trapping mechanisms will only begin at the end of several decades of gas injection, which implies that there is an imminent risk of discharge of large amount of gas in the event of a leak. This paper presents a method to fast-track and enhance residual and solubility trapping process while gas injection is in progress, such that only a fraction of the injected gas will migrate and be trapped beneath the cap rock after injection ceases. The method involves cyclic injection of gas and water (containing small amount of foaming agent). Foams are known to have gas trapping characteristics during flow in porous medium. A series of laboratory experiments was conducted on representative rock samples at different reservoir conditions. The results show a sequential and cumulative growth in trapped gas during cyclic injection of gas and foam based on in-situ and real time measurements of gas saturation in the samples using electrical resistivity tool. The amount of trapped (residual) gas depends on the type of gas (N2 or CO2), water salinity, concentration of the foaming agent, and temperature. The highest residual gas saturations (50%–70% of reservoir pore volume) occurred at a temperature and water salinity typical of a deep saline aquifer (45 °C and 58,000 ppm water). At a high water salinity of 242,000 ppm, the residual gas saturation was significantly lower (27%–30%). Similarly, at a high temperature of 90 °C, the residual gas saturation reduced to 27%. Residual gas could not be sustained when CO2 is injected compared to N2 because of the low interfacial tension between CO2 and water, which reduces the foam quantity and strength. The importance of foam stabilizing agents (e.g. polymers and nanoparticles) in addressing the observed shortcomings in CO2 foam and for foam injection in high salinity - high temperature reservoirs is discussed. A field scale application of this method is also highlighted.