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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

Contamination of surface waters with microbial pollutants from fecal sources is a significant human health issue. Identification of relative fecal inputs from the mosaic of potential sources common in rural watersheds is essential to effectively develop and deploy mitigation strategies. We conducted a cross-sectional longitudinal survey of fecal indicator bacteria (FIB) concentrations associated with extensive livestock grazing, recreation, and rural residences in three rural, mountainous watersheds in California, USA during critical summer flow conditions. Overall, we found that 86% to 87% of 77 stream sample sites across the study area were below contemporary Escherichia coli-based microbial water quality standards. FIB concentrations were lowest at recreation sites, followed closely by extensive livestock grazing sites. Elevated concentrations and exceedance of water quality standards were highest at sites associated with rural residences, and at intermittently flowing stream sites. Compared to national and state recommended E. coli-based water quality standards, antiquated rural regional policies based on fecal coliform concentrations overestimated potential fecal contamination by as much as four orders of magnitude in this landscape, hindering the identification of the most likely fecal sources and thus the efficient targeting of mitigation practices to address them.

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.

At the outlet of the Vermicelli catchment—a peri-urban area located in the campus of University of Calabria (Cosenza, Southern Italy)—a sedimentation tank is located, aiming at collecting the basin surface runoff and improve its quality. First, experimental results of the treatment effects are here presented and analyzed. In addition, a monitoring campaign was conducted in order to characterize the particles transported by surface runoff and to determine the treatment efficiency of the tank. The analysis showed the presence of a pollutant load in the surface runoff of the Vermicelli basin and provided information on its particle-size distribution (PSD). Results were considered in terms of the treatment efficiency of the sedimentation tank, showing a good overall removal efficiency value, together with a high variability of the removal sedimentation efficiency. This variability is mainly due to the different grain size of the suspended solids and the characteristics of the rainfall event.

The nutrient-rich liquid stream produced during the dewatering of digested biomass (i.e., the centrate) is commonly mixed with the influent raw wastewater at wastewater treatment facilities. This increases the nitrogen and phosphorus loading on biological processes, increases operating costs, and in some cases, results in increased nutrient concentrations in the final effluent. Forward osmosis (FO) is a membrane treatment process that was investigated at bench scale to determine its feasibility to concentrate centrate under both batch and continuous operating conditions. The continuous bench-scale system used FO as pretreatment for reverse osmosis (RO). Results demonstrated that high water flux and high nutrient rejection could be achieved. The combined FO/RO process exhibited sustainable flux over an extended time period. A mathematical model was developed in order to determine the specific energy, power, and membrane area requirements for a larger-scale centrate treatment process. Modeling results indicated that to optimize power and membrane area requirements, the system should be operated at approximately 70% water recovery.