Search Results (7)

Earth-Air Heat Exchangers (EAHEs) provide a compelling solution for improving building energy efficiency by harnessing the stable subterranean temperature to pre-treat ventilation air. This comprehensive review delves into the foundational principles of EAHE operation, meticulously examining heat and mass transfer phenomena at the ground-air interface. This study meticulously investigates the impact of key factors, including soil characteristics, climatic conditions, and crucial system design parameters, on overall system performance. Beyond independent applications, this review explores the integration of EAHEs with a diverse array of renewable energy technologies, such as air-source heat pumps, photovoltaic thermal (PVT) panels, wind turbines, fogging systems, water spray channels, solar chimneys, and photovoltaic systems. This exploration aims to clarify the potential of hybrid systems in achieving enhanced energy efficiency, minimizing environmental impact, and improving the overall robustness of the system. Full article

Problem statement: The study offers theoretical formulations for high-viscosity particulate flows in inclined reservoirs, taking into account the presence of homogeneous spheroidal particles of various types to produce discrete two-phase suspensions. Purpose: The primary objective of this analytical and comparative study is to identify the most dependable nanoparticles among hafnium and crystal metals that are suspended in an Eyring–Powell fluid through an inclined channel while being subjected to external magnetic and gravitational forces. Solution methodology: The flow dynamics of multiphase flows are formulated utilizing the stress tensor of the base fluid. The regular perturbation method (RPM) is employed to attain a more closed-form solution. The perturbation method is frequently employed in engineering problems to obtain an approximated solution, even when demonstrating the convergence of the solution is challenging. The rough solution is also validated through a thorough parametric analysis that shows the role of relevant parameters that contribute to the multiphase flow. Results: A concise parametric study is carried out against some of the most pertinent parameters and reveals that additional particles have promising effects on the momentum of each multiphase flow, whereas Eyring–Powell multiphase suspensions lessen in momentum due to strong internal viscous forces. The velocity of fluid and particle phases diminish with Hartmann number M and Froude number Fr. The second-order material constant B and concentration of nanoparticles C boost the motion of the fluid. The velocities of the particulate phase are quicker than the fluid phase. The hafnium particle is more reliable than crystal particles. Solution benchmark: Numerical and graphical findings have also been compared with the existing literature for the limiting case and found to be fully in agreement. Applications: This study’s findings provide a wider understanding of subterranean flows, specifically within the petroleum sector, with a focus on multiphase flows. Originality: The current study represents the authors’ original work and has not been previously submitted or published elsewhere. Full article

The Western Balkan’s Vjetrenica Cave in southern Bosnia and Herzegovina is renowned for high richness of subterranean species. However, the data on its fauna have been published only in monographs printed in a small number of copies, making them hardly accessible to the wider scientific community. To overcome this issue, we compiled the data from published monographs with the data from our own recent field surveys. Further, as they are connected via water channels or small crevices in bedrock, we defined the Vjetrenica Cave System as a system comprising Vjetrenica and Bjelušica Caves and Lukavac Spring. Altogether, 93 troglobiotic, i.e., obligate subterranean aquatic (48) and terrestrial (45), taxa were reported for the system, verifying the Vjetrenica Cave System as the second richest locality in subterranean biodiversity in the world. The global uniqueness of the system is also reflected in the fact that as many as 40 troglobiotic species were described from the system. Finally, we reviewed the factors endangering this unique subterranean community and questioned whether it will withstand human-induced changes and pressures due to infrastructural development in southern Bosnia and Herzegovina. Full article

In numerous subterranean projects, the impact of groundwater on the safety of the engineering undertaking is of paramount significance. Fractures, functioning as the primary channels for seepage within subterranean rock masses, necessitate the complex and challenging task of accurately characterizing seepage patterns and quantitatively investigating the effect of fissure parameters on fluid dynamics within the rock masses. This article presents a stochastic fissure model incorporated within a finite element framework, which captures the probabilistic distribution of fissures found in nature. It provides a comprehensive analysis of the distribution of pore water pressure and Darcy velocity fields. It unveils the permeation patterns of fissured rock masses and establishes a series of fissure models, quantitatively investigating the correlations between matrix permeability, water pressure, fissure density, fissure length, the length power law, fissure angle, the dispersion coefficient, fissure aperture, and the aperture power law, as well as their influence on the equivalent permeability of the rock mass. The findings reveal that in a discrete fissured rock mass, the greater the matrix permeability, the higher the equivalent permeability, and vice versa. Under water pressures of less than 10 MPa, gravity significantly impacts equivalent permeability, and permeability linearly increases with a rise in fissure density. Longer fractures result in higher permeability, and fractures parallel to the direction of water pressure contribute most significantly to the speed of seepage. Moreover, permeability markedly increases with an increase in aperture. This study provides a comprehensive analysis of the impact of matrix permeability and fissure parameters on equivalent permeability and calculates the permeability of each model. We also propose a set of predictive formulas based on fissure geometric parameters to anticipate the permeability of rock masses. Full article

In this paper, certain areas of the Kingdom of Saudi Arabia (KSA) are assessed in order to map potential geothermal energy zones. To evaluate high-resolution aerial magnetic data, spectral depth analysis using a modified centroid approach was used. The calculated geothermal parameters were gridded in order to delineate the regions characterised by a shallow Curie point depth (CPD) and a high geothermal gradient (GG) as well as a high heat flow (HF). The CPD, GG and HF calculated from the analysed data varied in the ranges of 6.0–15.0 km, 40.0–100.0 °C/km and 90.0–270.0 mW/m², respectively. The obtained results show the concurrence of the positions of shallow CPD (<8.0 km), high GG (>83.5 °C/km) and high HF (>211.0 mW/m²). The geothermal systems that are oriented in the E–W direction are related to the Red Sea tectonics, the tectonic opening of the Red Sea/Gulf of the Suez Rift, hot subterranean anomalies and high enthalpy from radioactive granites. Likewise, the geologic structures (fractures and faults) related to the Red Sea tectonics serve as channels for the movement of hydrothermal fluids and the deposition of associated minerals. All in all, another geophysical study involving deep boreholes, and seismic, magnetotelluric, electromagnetic and geochemical data should be conducted to evaluate and estimate precisely the economic reserves of geothermal resources. Full article

The aflaj systems represent unique irrigation technologies that have been implemented in the Sultanate of Oman. This innovative system, referred to as “falaj” in the singular form, is composed of a sophisticated network of underground tunnels and open-air channels designed to access shallow subterranean water tables, thereby providing water for residential and agricultural use. The aflaj systems have played a significant role in supporting sustainable water resource management in arid and semiarid regions, making a notable contribution to the socioeconomic development of the country. The alteration of land use and land cover (LULC) in arid and semiarid regions can have significant consequences for hydrological systems, affecting the ability of local ecosystems to manage fresh surface and groundwater resources. These changes are often caused by both natural and anthropogenic factors. To investigate the impact of LULC changes on aflaj systems in the northern part of Oman, we utilized satellite imagery, aflaj data, and spatial analytical and image processing techniques within the framework of geographic information systems (GIS) and remote sensing. In the first part of the study, we quantified the changes in LULC and their impact on aflaj systems in seven cities in Oman due to urban expansion. In the second part, we evaluated the effect of LULC on groundwater for four major aflaj between 1985 and 2021. The study area was divided into four primary LULC classifications: vegetation, bodies of water, metropolitan areas, and bare soil. The classification maps demonstrated a high overall accuracy of 90% to 95%, indicating satisfactory performance. Our results revealed a significant reduction in vegetation areas between 1985 and 2021, primarily shifting from bare soil (BS) to urban areas (UAs) and from vegetation cover (VC) to BS, due to the reduction of groundwater resources. Over the four study periods (1985–1990, 1990–2000, 2000–2013, and 2013–2021), the percentages of the total area of Falaj Al-Muyasser, Falaj Daris, Falaj Al-Maliki, and Falaj Al-Khatmeen that transformed from agricultural lands to UAs were 40%, 39%, 32%, and 8%, respectively. Our study highlights the need for appropriate land management and planning to ensure the most effective solutions are utilized to meet social and economic sustainability requirements. In conclusion, our study presents a comprehensive analysis of LULC changes and their impact on aflaj systems over a 36-year period, providing new insights into the potential effects of LULC changes on groundwater resources and offering a basis for informed decision making on land management in arid and semiarid areas. Full article

The pre-Columbian World Heritage site of Tiwanaku (AD 600–1100) located in highland altiplano Bolivia is shown to have a unique urban water supply system with many advanced hydraulic and hydrological features. By use of Computational Fluid Dynamics (CFD) modeling of the city water system, new revelations as to the complexity of the water system are brought forward. The water system consists of a perimeter drainage channel surrounding the ceremonial center of the city. A network of surface canals and subterranean channels connected to the perimeter drainage channel are supplied by multiple canals from a rainfall collection reservoir. The perimeter drainage channel provides rapid draining of rainy season rainfall runoff together with aquifer drainage of intercepted rainfall; water collected in the perimeter drainage channel is then directed to the Tiwanaku River then on to Lake Titicaca. During the dry season aquifer drainage continues into the perimeter drainage channel; additional water is directed into the drainage channel from a recently discovered, reservoir connected M channel. Two subterranean channels beneath the ceremonial center were supplied by M channel water delivered into the perimeter drainage channel that served to remove waste from the ceremonial center structures conveyed to the nearby Tiwanaku River. From control of the water supply to/from the perimeter drainage channel during wet and dry seasonal changes, stabilization of the deep groundwater level was achieved—this resulted in the stabilization of monumental ceremonial structure’s foundations, a continuous water supply to inner city agricultural zones, water pools for urban use and health benefits for the city population through moisture level reduction in city ceremonial and secular urban housing structures. Full article