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This study aims to investigate the water spray uniformity and collection ratio of sprinkler in an evaporative condenser of a water chiller. Experiments of water droplet distribution are conducted with 50 water collectors during the tests. Three different combinations of nozzle opening length and width were tested with the flow rates varied at 135 LPM and 176.4 LPM. Measured results show that the cross-sectional area of nozzle opening and flow rate significantly affect the water spray uniformity. In this work, at high flow rate, the Nozzle 2 with opening of 4 cm in length and 1 cm in width has better water spray uniformity compared to the nozzle 1 with opening of 4 cm in length and 0.7 cm in width. On the other hand, at low flow rate, the Nozzle 1 provides better impacting effect with the nozzle spacing of 17 cm, yet the Nozzle 2 performed better with the nozzle spacing of 15 cm. The latter case, with the smaller nozzle spacing and bigger nozzle opening size, led to a shorter impact distance of the spraying flow from two facing nozzles. Subsequently the spattering of water droplets was more pronounced, and distributed more uniformly. Keywords: Water spray uniformity, Collection ratio of sprinkler, Evaporative condenser, Nozzle opening

In this study, microwave-assisted hydrothermal carbonization of waste coconut shell (feedstock) is reported. It is a thermo-conversion technique in which the feedstock was transformed into energy-rich carbonaceous material under mild conditions. The process was conducted in a microwave oven by heating the waste coconut shell in deionized water inside a pressurized vessel. The effects of different process conditions on the product yields, and the energy properties of the hydrochars were studied by varying the reaction temperature from 150 to 200 °C and residence time from 5 to 30 min. The results showed that there was transformation of the feedstock in the process due to the decarboxylation, dehydration, and demethanation reactions. This led to changes in the chemical and structural compositions, as well as increase in the energy properties of the prepared hydrochars. The higher heating value increased from 15.06 MJ/kg in the feedstock to 19.76 MJ/kg in the hydrochar. The energy properties of the hydrochars prepared in this study showed that microwave-assisted hydrothermal carbonization process could be a technique for converting waste coconut shell into high value-added product.

Abstract Thermal energy storage (TES) can significantly increase the overall efficiency and operational flexibility of a distributed generation system. A sensible water storage tank is an attractive option for integration in building energy systems due to its low cost and high heat capacity. As such, this paper presents a model for stratified water storage that can be used in building energy simulations and distributed generation simulations. The presented model considers a pressurized water tank with two heat exchangers supplying hot and cold water respectively, where 1-D transient heat balance equations are used to determine the temperature profiles at a given vertical location. The paper computationally investigates the effect of variable flow-rates inside the heat exchangers, the effect of transient heat source, and buoyancy inside the tank induced by location and length of the heat exchangers. The model also considers variation in thermophysical properties and heat loss to the ambient. TES simulation results compare favorably with similar 1-D water storage tank simulations, and the buoyancy model presented agrees with COMSOL 3-D simulations. The analysis shows that when the inlet hot fluid temperature is time dependent, there is a phase lag between the stored water and the hot fluid temperature. Furthermore, it was observed that an increase in flow-rate inside the hot heat exchanger increases the stored water and the cold water outlet temperature; however, the increment in temperature observes diminishing returns with increasing flow-rate of hot fluid. It was also noted that for either heat exchanger, increasing the vertical height of the heat exchanger above a certain value does not significantly increase the cold fluid outlet temperature. Results from the model simulations can assist building designers to determine the size and configurations of a thermal storage tank suited for a given distributed generation system, as well as allowing them to accurately predict the fraction of heat generated by the system that could be stored in the tank at a given time when charging, or the fraction of heating load that could be met by the tank when discharging.

Abstract Flow-through experiments in the laboratory were conducted to monitor the fate of CO2 using stable carbon isotope (δ13C) techniques in dynamic, pre-equilibrium conditions. Such conditions are typical, for instance in carbon capture storage (CCS), in the initial stages of CO2 injection, near injection well regions of the reservoir. For this purpose, a reactive percolation bench (ICARE 4) was used, injecting a CO2-saturated brine at supercritical conditions (pCO2 = 84 bar, T = 60 °C) through quartzitic limestone at an average flow rate of 2 × 10− 9 m3 s− 1. Calcium (Ca2 +) and dissolved inorganic carbon (DIC) concentration data and pH were used to aid analytical interpretations. During CO2 injection, δ13CDIC values decreased from about − 11‰ to those of the injected CO2 (− 29.3‰), indicating CO2 sourced carbon dominance over a carbonate sourced one in the system. Simultaneously DIC and Ca2 + concentrations increased from 1 mmol L− 1 to a maximum of 71 mmol L− 1 and 31 mmol L− 1, respectively. Isotope and mass balances were used to quantify the amount of DIC originating from either the injected CO2 or carbonates. At the end of the experiments, between 70 and 98% of the total DIC originated from CO2 dissolution, the remaining amount is attributed to carbonate dissolution. Furthermore, the total amount of injected CCO2 trapped as DIC ranged between 9 and 17% and between 83 and 91% was in free phase. The state of carbonate equilibrium of the host fluid, under the high pressure–temperature conditions after CO2 injection was identified, verifying pre-equilibrium conditions. Results confirm observations made in reported field data. This emphasises that the combination of CO2 monitoring, the development of a thorough understanding of carbonate equilibrium, as well as the quantification of CO2-trapping, is essential for a solid assessment of reservoir performance and safety considerations during CO2 injection. These are equally important for understanding water–rock–CO2 dynamics in natural subsurface environments.

This paper studies the effectiveness of applying value engineering to actual concrete mixtures. The study was conducted in the State of Qatar on a number of strategic construction projects with international engineering specifications for the 2022 World Cup projects. The study examined the concrete mixtures of Doha Metro project and the development of KAHRAMAA’s (Qatar Electricity and Water Company) Abu Funtas Strategic Desalination Plant, in order to generally improve the quality and productivity of ready-mixed concrete used in construction and hydraulic projects. The application of value engineering to such concrete mixtures resulted in the following: • Improving the quality of concrete mixtures and increasing the durability of buildings in which they are used; • Reducing the waste of excess materials of concrete mixture, optimizing the use of resources, and enhancing sustainability; • Reducing the use of cement, thus reducing CO2 emissions which ensures the protection of environment and public health; • Reducing actual costs of concrete mixtures and, in turn, reducing the costs of construction projects; and • Increasing the market share and competitiveness of concrete producers. This research shows that applying the methodology of value engineering to ready-mixed concrete is an effective way to save around 5% of the total cost of concrete mixtures supplied to construction and hydraulic projects, improve the quality according to the technical requirements and as per the standards and specifications for ready-mixed concrete, improve the environmental impact, and promote sustainability.

Abstract The effect of steam on the buffer material used in high-level radioactive waste (HLW) repositories has led to incessant uncertainty on the safety assessment because of the likelihood of loss in isolating potential. Hydraulic properties of compacted bentonite during vapor treatment is not fully and directly understood because of the difficulty of performing necessary tests under repository conditions. This article presents a vapor testing device conceived of and developed to monitor the evolution of swelling pressure and gas pressure during steam treatment and hydraulic conductivity after treatment under constant volume conditions. Although heat lag and thermal expansion were observed, the heating procedures were cautiously controlled and the swelling pressures were corrected, accordingly. Furthermore, the hydraulic properties of compacted bentonite during and after treatment were tested with a water-to-solid ratio of 1.3 and at different temperatures. Overall, the developed apparatus has demonstrated itself as an effective tool to better comprehend the interaction between bentonite and water vapor as regards to the temperature gradient and boundary conditions.

Agricultural plant wastes such as wheat straw, rice hulls, and sunflower-seed husks were characterized experimentally. The chemical composition of the ash formed from these wastes at various temperatures was determined by energy-dispersive X-ray microanalysis, X-ray diffraction analysis, and IR spectroscopy. The chemical composition of mineral components of the agricultural plant waste ash varies, but the prevalent components are CaO, SiO2, and K2O. Thermodynamic calculations show that SiO2 prevails in rice hull ash; K2Si2O5 and Ca3Si2O7, in wheat straw ash; and potassium compounds (K2O, K2SiO3, KCl, K2SO4), in sunflower-seed husk ash. The ash melting temperatures were determined by the method of characteristic temperatures. No clear correlation was revealed between the melting temperature and alkali metal content of the ash. The main parameters of slag formation such as base–acid ratio, slag viscosity index, and fouling coefficient were calculated. Wheat straw ash and sunflower-seed husk ash, in contrast to rice hull ash, tend to slagging and fouling of reactor walls.

The booming development and production of shale gas largely depends on extensive application of water-based hydraulic fracturing treatments and primary pressure depletion. Issues associated with this procedure include fast production rate drop, low recovery factor, high water consumption, and formation damage. It is necessary to develop new reservoir fracturing and enhanced gas recovery (EGR) technologies to reduce water usage and resource degradation, guarantee the environmental sustainability of unconventional resource developments, and boost individual well production. Building on gas storage and transport mechanisms in shales, this study investigated the feasibility of a new CO2-based reservoir treatment technology. CO2 has a higher adsorptivity than CH4, enabling it to liberate adsorbed natural gas in place. Therefore, gas production will be boosted by injecting CO2 to replace CH4. This novel reservoir treatment process will also open a large market for the beneficial utilization of CO2. In this paper, the authors discuss the theoretical principles and feasibility of using CO2 in both the stimulation stage and the secondary gas recovery stage. Following that, the authors outline a case study performed to simulate applying the CO2-EGR process in the Barnett, Eagle Ford, and Marcellus shale plays. The marginal revenue per thousand standard cubic feet (MSCF) of increased CH4 production was calculated. The profitability was found to be largely determined by the prices of natural gas and available CO2. A cost break-down analysis indicated that the CO2 procurement expense was the main component in the total cost. The proposed CO2-EGR process was mostly like to be successful in the Barnett shale.

Toxic pyrrolizidine alkaloids (PAs) are found in tea samples, which pose a threat to human health. However, the source and route of PA contamination in tea samples have remained unclear. In this work, an adsorbent method combined with UPLC-MS/MS was developed to determine 15 PAs in the weed Ageratum conyzoides L., A. conyzoides rhizospheric soil, fresh tea leaves, and dried tea samples. The average recoveries ranged from 78%-111%, with relative standard deviations of 0.33%-14.8%. Fifteen pairs of A. conyzoides and A. conyzoides rhizospheric soil samples and 60 fresh tea leaf samples were collected from the Jinzhai tea garden in Anhui Province, China, and analyzed for the 15 PAs. Not all 15 PAs were detected in fresh tea leaves, except for intermedine-N-oxide (ImNO) and senecionine (Sn). The content of ImNO (34.7 µg/kg) was greater than that of Sn (9.69 µg/kg). In addition, both ImNO and Sn were concentrated in the young leaves of the tea plant, while their content was lower in the old leaves. The results indicated that the PAs in tea were transferred through the path of PA-producing weeds-soil-fresh tea leaves in tea gardens.