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Capillary Forces in Fluid Flow in Porous Solids (Shale Formations)
Published in K.S. Birdi, Surface Chemistry and Geochemistry of Hydraulic Fracturing, 2016
Experiments have shown that the most important parameter as regards the flow of a liquid in a porous medium is the capillary pressure. This has been extensively investigated in the literature for over a century (Scheludko, 1966; Goodrich et al., 1981; Birdi, 1999; Somasundaran, 2015). It is of interest to analyze a system in which a liquid comes into contact with a solid surface. Let us consider aspects in the field of wettability. Surely, everybody has noticed that water tends to rise near the walls of a glass container. This happens because the molecules of this liquid have a strong tendency to adhere to the glass. Liquids that wet the walls make concave surfaces (e.g., water/glass); those that do not wet them make convex surfaces (e.g., mercury/glass). Inside tubes with an internal diameter smaller than 2 mm, called capillary tubes, a wettable liquid forms a concave meniscus in its upper surface and tends to go up along the tube. In contrast, a nonwettable liquid forms a convex meniscus, and its level tends to go down. The amount of liquid attracted by the capillary rises till the forces that attract it balance the weight of the fluid column. The rising or lowering of the level of the liquids into thin tubes is named capillarity (capillary force). One notices that a liquid inside a large beaker is almost flat at the surface. However, the same liquid inside a fine tube will be found to be curved (Figure 2.5). The rise in height is found to be dependent on the radius of curvature. The capillary rise is higher in the narrow tube. This behavior is very important in everyday life. For example, in the case of oil or gas recovery, the most important characteristic is the pore size of the reservoir rock (which determines the capillary force). The physical nature of this phenomenon will be the subject of this section.
A review of performance improvements in design features of liquid flat-plate solar collector
Published in International Journal of Green Energy, 2023
Yogesh Kumar, Manoj Verma, Harish Kumar Ghritlahre, Satish Kumar, Priyanka Verma, Shiena Shekhar
Bhowmik and Amin (2017) developed an FPSC prototype (with and without a solar reflector) and conducted experiments to enhance TE (Figure 14). Mirror or mercury glass-made solar reflector positioned on both sides of the collector such that it may modify its location in response to the sun’s position. Solar collectors are positioned in such a way that they should be able to gather both direct and diffuse sunlight since both types of energy are directed toward them by solar reflectors. Volume flow rate was maintained between 0.1 and 0.2 l/min. Reflector and collector surfaces were chosen to be 1.85 m2 and 1.05 m2, respectively, with 430 W/m2 and 0.9 taken for sun intensity and mirror reflectivity. At 12.30 p.m. on a day with a maximum solar intensity of 430 W/m2, the maximum output water temperature and efficiency of FPSC were measured as 50°C and 47°C and 61% and 51%, respectively. The collector efficiency is increased by around 10% when using solar reflectors.
Nitrifying bio-cord reactor: performance optimization and effects of substratum and air scouring
Published in Environmental Technology, 2019
Xin Tian, Warsama Ahmed, Robert Delatolla
The following parameters were tested in triplicate in the reactors throughout the study: -N, , , sCOD, TSS, volatile suspended solids (VSS), DO, pH and temperature. All nitrogen constituents and solids were measured in accordance with standard methods [30]. In particular, the following methods were used in this study: 4500-NH3, 4500- B, 4500-, 2540 D-TSS (TSS dried at 103–105°C) and 2540 E-Volatile Solids and VSS (fixed and volatile solids ignited at 550°C). The sCOD was analyzed using a DR 5000 spectrophotometer (HACH, Loveland, CO) after 0.45 μm filtration using a Millipore G filter. DO, pH and temperature were measured using a Multi Parameter Meter with an attached DO probe and pH probe (VWR, Canada, Ontario), and a mercury glass thermometer, respectively.