Search Results (11)

Nanomaterials have attracted attention for application in photocatalytic hydrogen production because of their beneficial properties such as high specific surface area, attractive morphology, and high light absorption. Furthermore, hydrogen is a clean and green source of energy that may help to resolve the existing energy crisis and increasing environmental pollution caused by the consumption of fossil fuels. Among various hydrogen production methods, photocatalytic water splitting is most significant because it utilizes solar light, a freely available energy source throughout the world, activated via semiconductor nanomaterial catalysts. Various types of photocatalysts are developed for this purpose, including carbon-based and transition-metal-based photocatalysts, and each has its advantages and disadvantages. The present review highlights the basic principle of water splitting and various techniques such as the thermochemical process, electrocatalytic process, and direct solar water splitting to enhance hydrogen production. Moreover, modification strategies such as band gap engineering, semiconductor alloys, and multiphoton photocatalysts have been reviewed. Furthermore, the Z- and S-schemes of heterojunction photocatalysts for water splitting were also reviewed. Ultimately, the strategies for developing efficient, practical, highly efficient, and novel visible-light-harvesting photocatalysts will be discussed, in addition to the challenges that are involved. This review can provide researchers with a reference for the current state of affairs, and may motivate them to develop new materials for hydrogen generation. Full article

Three-dimensional computational analysis has been performed to investigate the melting time of the phase change material (PCM) in a sinusoidal pipe inserted into another pipe. The other pipe is filled with PCM and the system is heated from the inner sinusoidal pipe at different temperatures. The main aim of the study is to control the melting time. The finite volume method (FVM) is used to solve time-dependent governing equations. Four different cases are chosen for the sinusoidal wall to see the effects of geometry on melting. After the analysis, it is observed that melting time can be controlled via an adjustment of the geometrical parameter, namely a passive technique, without spending extra energy. Full article

This review is about non-Newtonian nanofluid applications for convection in cavities under a magnetic field. Convection in cavities is an important topic in thermal energy system, and diverse applications exist in processes such as drying, chemical processing, electronic cooling, air conditioning, removal of contaminates, power generation and many others. Some problems occur in symmetrical phenomena, while they can be applicable to applied mathematics, physics and thermal engineering systems. First, brief information about nanofluids and non-Newtonian fluids is given. Then, non-Newtonian nanofluids and aspects of rheology of non-Newtonian fluids are presented. The thermal conductivity/viscosity of nanofluids and hybrid nanofluids are discussed. Applications of non-Newtonian nanofluids with magnetohydrodynamic effects are given. Different applications of various vented cavities are discussed under combined effects of using nanofluid and magnetic field for Newtonian and non-Newtonian nanofluids. The gap in the present literature and future trends are discussed. The results summarized here will be beneficial for efficient design and thermal optimization of vented cavity systems used in diverse energy system applications. Full article

This study aims to design and optimize a backup renewable energy station and possibility of the grid-connected hybrid photovoltaic (PV) power system for firms in 2nd Jeddah industrial city workshops. Wind and solar energy potentials were examined, and data from a variety of sources were obtained as part of the study process. It is important to utilize the application hybrid optimization model for electric renewables (HOMER) to evaluate relevant data as well as the suggested hybrid power system’s economic feasibility. The system’s payback is solely based on monthly grid bill savings and increased profits due to the absence of a power shortage. The most cost-effective system design is measured in terms of the original cost, ongoing cost, cost per unit, and total system net present value. As a result, fulfilling the load demand with 220 kW wind turbines and 500 kW solar PV is both cost-effective and efficient. The simulation results for the second scenario with a wind turbine show that a combination of a 500 kW PV, 300 kWh battery capacity, 22 kW wind turbine, and 315 kW converter is the most feasible solution for this case study, with SAR 4,433,658 net present cost (NPC) and SAR 0.1741 LCOE. Full article

Air conditioning (AC) is considered an important requirement for hot environments, but it is facing one of the most demanding obstacles as concerns the use of electrical energy resources. In 2019, electricity consumption in the residential sector in Gulf Cooperation Council states reached approximately 43% of the total national consumption, and about two-thirds of the electrical energy consumed in residential buildings (RBs) was used for AC. Therefore, as these indicators show, there is a need to focus on studying AC. One of the most important reasons for the high consumption of electrical energy in RBs is the big difference between indoor and outdoor temperatures. In this paper, a heat exchanger was designed and tested experimentally to reduce this temperature difference by using a domestic ground water tank (GWT) as a sink/source (water-cooled condensers instead of air-cooling). The results have shown that the water tank made the surrounding temperature around the external coil of the AC more suitable for cooling/heating. The proposed system resulted in a reduction in energy consumption by 28% of the electrical energy needed in the conventional system and an increase in COP by 39%. This means that this system is more efficient and therefore more sustainable. Full article

This paper presents a modelling of nanofluid flow using Caputo fractional derivatives through conservative equations of mass and momentum, and provides an exact solution on un-steady convective flow over a vertical plate with the mass diffusion effect, in association with an energy equation. H₂O is the base liquid with clay nanoparticles floating in it in a uniform way. Boussinessq’s approach is used in the momentum equation for pressure gradient. The non-dimensional fluid temperature, species concentration and fluid transport are derived together with Jacob Fourier sine and Laplace transform techniques in terms of exponential decay function, and the inverse is computed further in terms of the Mittag-Leffler function. The impact of various physical quantities is interpreted with the fractional order of the Caputo derivatives. The obtained temperature, transport and species concentration profiles show behaviors for 0 < $\mathsf{\alpha }$ < 1, where $\mathsf{\alpha }$ is the fractional parameter. The rate of heat and mass transfer coefficients for the significance of physical quantities of interest are also obtained and presented through graphs. The impact of the nanoparticle volume fraction on the flow field is observed. At larger values of the fractional parameter, the velocity, temperature, and concentration distributions grow more quickly. In addition to that, it is found the concentration profiles behave in the opposite way for the volume fraction of nanofluids. Full article

Photocatalysts lead vitally to water purifications and decarbonise environment each by wastewater treatment and hydrogen (H₂) production as a renewable energy source from water-photolysis. This work deals with the photocatalytic degradation of ciprofloxacin (CIP) and H₂ production by novel silver-nanoparticle (AgNPs) based ternary-nanocomposites of thiolated reduce-graphene oxide graphitic carbon nitride (AgNPs-S-rGO_2%@g-C₃N₄) material. Herein, the optimised balanced ratio of thiolated reduce-graphene oxide in prepared ternary-nanocomposites played matchlessly to enhance activity by increasing the charge carriers’ movements via slowing down charge-recombination ratios. Reduced graphene oxide (rGO), >2 wt.% or <2 wt.%, rendered H₂ production by light-shielding effect. As a result, CIP degradation was enhanced to 95.90% by AgNPs-S-rGO_2%@g-C₃N₄ under the optimised pH(6) and catalyst dosage(25 mg/L) irradiating beneath visible-light (450 nm, 150 watts) for 70 min. The chemical and morphological analysis of AgNPs-S-rGO_2%@g-C₃N₄ surface also supported the possible role of thiolation for this enhancement, assisted by surface plasmon resonance of AgNPs having size < 10 nm. Therefore, AgNPs-S-rGO_2%@g-C₃N₄ has 3772.5 μmolg⁻¹ h⁻¹ H₂ production, which is 6.43-fold higher than g-C₃N₄ having cyclic stability of 96% even after four consecutive cycles. The proposed mechanism for AgNPs-S-rGO_2%@g-C₃N₄ revealed that the photo-excited electrons in the conduction-band of g-C₃N₄ react with the adhered water moieties to generate H₂. Full article

The current article presents the entropy formation and heat transfer of the steady Prandtl-Eyring nanofluids (P-ENF). Heat transfer and flow of P-ENF are analyzed when nanofluid is passed to the hot and slippery surface. The study also investigates the effects of radiative heat flux, variable thermal conductivity, the material’s porosity, and the morphologies of nano-solid particles. Flow equations are defined utilizing partial differential equations (PDEs). Necessary transformations are employed to convert the formulae into ordinary differential equations. The implicit finite difference method (I-FDM) is used to find approximate solutions to ordinary differential equations. Two types of nano-solid particles, aluminium oxide (Al₂O₃) and copper (Cu), are examined using engine oil (EO) as working fluid. Graphical plots are used to depict the crucial outcomes regarding drag force, entropy measurement, temperature, Nusselt number, and flow. According to the study, there is a solid and aggressive increase in the heat transfer rate of P-ENF Cu-EO than Al₂O₃-EO. An increment in the size of nanoparticles resulted in enhancing the entropy of the model. The Prandtl-Eyring parameter and modified radiative flow show the same impact on the radiative field. Full article

PTSCs (parabolic trough solar collectors) are widely employed in solar-thermal applications to attain high temperatures. The purpose of this study is to determine how much entropy is created when Powell-Eyring nanofluid (P-ENF) flows across porous media on a horizontal plane under thermal jump circumstances. The flow in PTSC was generated by nonlinear surface stretching, thermal radiation, and Cattaneo-Christov heat flux, which was utilized to compute heat flux in the thermal boundary layer. Using a similarity transformation approach, partial differential equations were converted into ordinary differential equations with boundary constraints. Then, the boundary restrictions and partial differential equations were merged to form a single set of nonlinear ordinary differential equations. To obtain approximate solutions to ordinary differential equations, the Keller-Box approach is utilized. Nanofluids derived from silver- and copper-based engine oil (EO) has been employed as working fluids. The researchers observed that changing the permeability parameter reduced the Nusselt number while increasing the skin frictional coefficient. Total entropy variation was also calculated using the Brinkman number for flow rates with Reynolds number and viscosity changes. The key result is that thermal efficiency is inversely proportional to particular entropy production. For example, using Cu-EO nanofluid instead of Ag-EO nanofluid increased the heat transport rate efficiency to 15–36%. Full article

Nanofluids have better surface stability, thermal absorption, and distribution capacities are produced as heat transfer fluids. In current nanofluid-transport studies, together with the heat transfer mechanisms, entropy reduction in thermo- and non-Newtonian nanofluid models with changing thermophysical characteristics is heavily addressed. The entropy production is examined as thermodynamically stable first-grade viscoelastic nanofluid (FGVNF) flow over a flat penetrable, porous barrier. The uniform porous horizontal stretching of the surface in a Darcy type of pore media results in a fluid motion disturbance. In addition, this study also includes the effects of thermal radiation, viscous dissipation, and slip conditions at the border. Under boundary layer flow and Rosseland approximations, the governing mathematical equations defining the physical features of the FGVNF flow and heat transfer models are summarized. The governing nonlinear partial differential equation is transformed by similarity variables to achieve solutions in nonlinear ordinary differential equations. Approximative solutions for reduced ordinary differential equations are obtained by the Keller Box Scheme. Two distinct types of nanofluids, Copper-Engine Oil (Cu-EO) and Zirconium Dioxide-Engine Oil (ZrO₂-EO), are considered in this research. The graphs are produced to examine the effects of the different physical factors for the speed, temperature, and entropy distributions. The significant findings of this study are that the critical characteristics of (boundary layer) BL collectively promote temperature variation, including slip speed, diverse thermal conductivity, and non-Newtonian first-grade viscoelastic nanofluid, the concentration of nanoparticles as well as thermal radiation, and a high porous media. The other noteworthy observation of this study demonstrates that the (Cu-EO) FGVNF is a better conductor than (ZrO₂-EO) FGVNF transmission. The entropy of the system grows the Deborah number and volume fraction parameter. Full article

Twenty percent of the world’s energy is consumed by the construction sector, including commercial and residential buildings, where 13% is consumed by the residential sector only. Half of the total energy consumed by buildings in Saudi Arabia is specifically attributed to the hot summer season, which, unlike in many other countries in the Middle East, continues for more than 5 months annually. The use of a phase change material (PCM), as an insulator in building materials, can be a solution to provide a comfortable indoor temperature and reduce energy consumption. This study examined two different melting ranges for PCMs RT35 and RT35HC inserted into hollow clay bricks to investigate their thermal behavior and heat storage capacity and compare them with polystyrene foam. To perform this experiment, four chambers were constructed using cement plastering. The data were collected at Jeddah, Saudi Arabia, from mid-November 2020 to the end of February 2021. When the highest temperature was reached during the experiment, PCM RT35 provided a better cooling effect by 13% compared to 24% and 28.56% for PCM RT35HC and foam, respectively, compared to hollow bricks alone. However, when the lowest temperature was reached during the experiment, PCM RT35HC performed better than the other chambers in saving energy and keeping the chamber warm, which was 9.5% for the reference chamber, 7.0% for the foam chamber, and 2.8% for PCM RT35. The maximum energy saving of PCM RT35 was around 1920 kJ, which is around 0.533 kWh, for one wall only, and for PCM RT35HC, it was 2880 kJ, or 0.8 kWh, which can reduce energy consumption of the HVAC system by 97 kWh/m² and 146 kWh/m² per year, respectively. Full article