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Aviation fuels are essential for flight transportation. The increasing demand for such fuels threatens the present efforts to mitigate global warming. Changing to renewable energy sources and hydrogen to drive airplanes is not ready and will take a few decades. Therefore, alternative fuels such as sustainable aviation fuels (SAFs, also so-called bio-jet fuels) could play an excellent role in mitigating greenhouse emissions. SAFs encompass blends of bio and synthetic fuels. Some SAF pathways have already been certified (such as oil-to-jet, alcohol-to-jet, gas-to-jet, and sugar-to-jet), and some are on the way to being certified. This review starts by providing a detailed overview of the current status of aviation fuels, including their growth, types, and emission trends. After that, it comprehensively delves into a thorough discussion of SAFs, covering various aspects such as their types, combustion properties, production technologies and pathways, cost evolution, and life cycle assessments. The paper discusses the SAFs' future prospects while providing practical recommendations based on the analysis. It was shown that the oil-to-fuel (HEFA) pathway is more mature with less carbon emissions. SAFs face challenges, including high costs, limited production scale, feedstock availability, energy-intensive production methods, land-use competition, potential indirect environmental impacts, certification standards, infrastructure, and public acceptance. Much research is needed to reduce SAF costs substantially less than conventional aviation fuels. [ABSTRACT FROM AUTHOR]

Roadside data collecting and communication applications might all benefit from power produced by energy harvesting from highways. According to the energy source they tap, roadside energy harvesters may be roughly divided into three categories: solar radiation, pavement heat, and mechanical energy from moving automobiles. In addition to environmental issues like the heat island impact on cities, asphalt pavements exposed to sun radiation may reach high temperatures that result in structural damage from hardening or rutting resulting from heat cycles. Asphalt solar collectors (ASCs) are one of the types of active systems that are doubly effective since they alleviate the difficulties that were described before and. Furthermore, ASCs can capture energy that can be utilized in a variety of different applications. To provide a complete picture of recent scientific developments, this review covers numerical, experimental, and numerical and experimental research on ASCs. Specifically, the setup, design parameters, advancement, challenges, and mathematical modeling of ASCs are systematically discussed. Accordingly, a number of suggestions for further research projects have been made in light of the associated results. [ABSTRACT FROM AUTHOR]

The present paper focuses on a review recalling the main contributions of studies that involve nanofluids on automotive industry. The novelty of the paper consists on the concise synthesis presented, that highlights new tested nanofluids in several applications in automotive. The review includes critics on the efficiency, the impact on material and the environmental issues when nanofluids are used as fuel. Three main sections are presented, which deploy the use of nanofluids as coolant in a car radiator, addition in the fuel or engine oil and finally the last section reviews the assessment of the wear effects of nanofluids on materials used in a car coolant system and in the car engine. The current review emphasized some major findings and critics: (1) The contradictory conclusions denoted about the effect of volume concentration on pumping power loss and the Nusselt number in a car radiator system. (2) Remarkable discrepancies in the determination of the optimal nanoparticles volume concentration and the precise heat transfer enhancement. (3) The viscosity of a nanolubricant needs a deep analysis to determine the optimal value that ensures the best lubricant film between components in a car engine. (4) Some mechanical problems should be analyzed when using nanofluids in fuel. [ABSTRACT FROM AUTHOR]

This study deals with mixed convection of Al 2 O 3 –Cu–water hybrid nanofluid in a wavy channel having a circular cylinder. A two-dimensional system of partial differential equations has been discretized by employing Galerkin finite element method. Numerical simulations are carried out for different ranges of the governing parameters such as Reynolds number ( 10 ≤ Re ≤ 200 ), nanoparticle volume fraction ( 0.01 ≤ ϕ ≤ 0.05 ) and wave amplitude ( 0.05 ≤ A ≤ 0.25 ). It is inferred that Reynolds number is a key factor in this study. As it rises, the fluid behavior switches from slower to faster mode. Average Nusselt number rises at lower wavy wall and with lift coefficient ( C L ). The highest average Nusselt number is achieved at A = 0.05 , which is promoting the heat transfer by roughly 200 % . Furthermore, an enhancement in the nanoparticle volume fraction leads to the decrease in the local Nusselt number on upper wavy wall. The flow philosophy is presented in the form of isotherm contours, streamline contours and some appropriate plots. [ABSTRACT FROM AUTHOR]

The present study aims at estimating the values of an electrochemical model parameter of a proton exchange membrane fuel cell (PEMFC). A variant of the particle swarm optimization (PSO) algorithm is adopted. This variant introduces a constriction coefficient to better regulate the convergence of the numerical code. Parameters' identification of the PEMFC stack model is performed by specifying a range for each. Validity of the adopted approach is confirmed by confronting simulation results with experimental data in terms of current–voltage polarization curves. It should be noted that the optimal value of the objective function is largely affected by the lower and upper values of the parameters. Comparison of present results with other optimization methods shows a noticeable improvement in PEMFC stack performance when using particle swarm optimization algorithm with constriction coefficient (PSO-χ). This confirms that this version of PSO algorithm is very suitable for the optimization and parameter estimation of PEMFC stack modeling. [ABSTRACT FROM AUTHOR]

An experimental and numerical investigation of a small linear Fresnel for water heating application has been carried out in Blida, Algeria. The numerical simulation with a 1D modeling in transient mode was performed by using the finite difference method. The thermal evaluation is based on the energy assessments characterized by the differential equations of pure water with a flow mass rate equal to 0.015 kg s−1 and copper absorber tube temperature. Moreover, the Fluent code has been developed in order to conduct the CFD modeling at the absorber tube of the solar collector. SolTrace software has been used to determine the optical behavior of the linear reflector. The average optical efficiency of the device is about 42.97%, but the average value of the experimental thermal efficiency reached 29.21% for 22/01/2015 and 29.20% for 19/02/2015. The average value of pure water temperature for 22/01/2015 is 67.28 °C, while its value for 19/02/2015 is 70.99 °C. This solar experimental setup will reduce the consumption of liquefied natural gas by 88.9 m3, which will reduce the CO2 emission by 187.93 kg. In addition, its manufacturing cost will be recovered 16 years from the date of use of this heater. [ABSTRACT FROM AUTHOR]

The electro-thermo-convection in a square cavity with incorporated hot solid body is numerically investigated. The finite volume method associated with Patankar's "blocked-off-regions" technique is applied. A potential difference is applied between the hot obstacle and the horizontal walls in order to eliminate the so-called dead zone created at the bottom of the cavity. The flow movement is induced not only by thermal buoyancy forces but also by the electric Coulomb force. Calculations are made for several injection levels (1 ≤ C ≤ 10), various obstacle shape factors (1 ≤ l/w ≤ 9), different number of electric Rayleigh (0 ≤ T ≤ 800), multiple thermal Rayleigh numbers (2000 ≤ Ra≤ 30,000) and 03 obstacle positions. The results show that according to the intensity of the applied electrical forces, two types of regimes are identified: a thermally dominated regime characterized by a low heat exchange at the bottom of the obstacle and conversely an electrically dominated regime with an excellent heat exchange over the entire cavity. It has been demonstrated that it is possible to improve the heat transfer up to: 43% by changing the shape factor of the obstacle; 82% by varying the injection level and 532% by applying electrical forces. [ABSTRACT FROM AUTHOR]

The present study summarizes a two-dimensional (2D) numerical simulation of a phase change material (PCM) melting/solidification processes in a square cavity. The objectives of this study are to study and compare the effect of the application of different applied thermal boundary conditions such as constant or variable thermal flux during the melting and solidification processes of a PCM. Here, the convective heat transfer is taken into account according to the Boussinesq approximation. The commercial code COMSOL Multiphysics is used, and the "Voller model" based on the enthalpy-porosity technique is applied on a fixed computational grid. Results presented in terms of solid–liquid fraction, flow structure, isotherms, and stored and released thermal energy have shown that the melting time for the applied variable heat flux is reduced compared to that of constant heat applied flux. In addition, it was found that the PCM melting time was shorter than the solidification time. Therefore, the use of variable (sinusoidal) heat flux conditions can be useful in engineering applications such as thermal energy storage applications (PCM life cycle test, solar energy where a variable heat flow is involved due to the change of day). [ABSTRACT FROM AUTHOR]

The laminar two-dimensional mixed convection in a trapezoidal enclosure with a rotating inner circular cylinder and a sinusoidal bottom wall is studied numerically. The fluid inside the enclosure is a CuO–water nanofluid layer in the top space of it, while the bottom space includes a CuO–water nanofluid saturated with a porous medium. Both the right and left sidewalls are assumed adiabatic, while the bottom and the top walls of the enclosure are maintained, respectively, at the hot and cold temperatures. The dimensionless governing equations are expressed for velocity and temperature formulation and modeled by using COMSOL code based on the Galerkin finite element method. Parametric studies on the effects of various significant parameters such as Rayleigh number, Darcy number, the inner cylinder radius, the porous layer thickness, the angular rotational velocity, the solid volume fraction and the number of undulations on the flow and thermal fields together with the heat transfer rate have been performed. The highest value of the stream function for (Ra = 103 and Ra = 105) is seen at (R = 0.2 and S = 0.2). The same thing is observed, when the bottom wall is considered wavy. For (Ra = 103 and N = 0) and (0.5 ≤ S ≤ 0.8), it can be seen that as the inner cylinder radius increases from (R = 0.1) to (R = 0.3), the stream function values increase continuously. It is found that the average Nusselt number increases as the Rayleigh and Darcy numbers, the solid volume fraction, inner cylinder radius and the angular rotational velocity of the cylinder increase, while it decreases as the porous layer thickness and the number of undulations increase. Comparisons with previously published numerical works are performed, and good agreements between the results are observed. [ABSTRACT FROM AUTHOR]

Three-dimensional numerical simulation on natural convection inside the T-shaped cavity, filled with water-based hybrid nanofluid of CNT–aluminum oxide is performed by vorticity–vector potential formalism. The variables considered are size of enclosure (0.1 < L < 0.9), volumetric percentage of nanoparticles (0 < φ < 4%), fraction of CNT composites (0 < fr < 1), and Rayleigh number (103 < Ra < 106). The heat transfer is increased with the increase in size, volumetric percentage of nanoparticles, fraction of CNT composites, and Rayleigh number. [ABSTRACT FROM AUTHOR]

A steady laminar two-dimensional magneto-hydrodynamics mixed convection flow in a square inclined cavity filled with Cu–water nanofluid is investigated numerically by using the finite difference method. The left and right vertical sidewalls of the cavity are considered adiabatic and move upward, while a partial slip flow condition is imposed on these walls. The horizontal top wall is considered cold and stationary, while a part of the stationary bottom wall is subjected to a uniform heat source and the remaining parts of it are considered adiabatic. An adiabatic obstacle is located in the center of the cavity and an external magnetic field is applied parallel to the horizontal x-axis. Parametric studies of the influence of various parameters such as Hartmann number, inclination angle of the cavity, dimensionless heat generation/absorption coefficient, obstacle aspect ratio, dimensionless length and location of the heat source, and solid volume fraction on the fluid flow and heat transfer have been performed. Comparisons with previously published numerical work are performed, and good agreements between the results are observed. It is found that the nanofluid was better than water to enhance the heat transfer when the effect of the magnetic field is weak, while the water is better than the nanofluid when its effect is strong. Moreover, the results indicated that the partial slip has a significant effect on the above-mentioned parameters. [ABSTRACT FROM AUTHOR]

In the original publication of the article, under the section 'Affiliation' number 1, the sentence that read as "Department of Industrial Engineering and Systems, College of Engineering, Princess Noura bint Abdu Rahman University, Riyadh, 84428, Saudi Arabia" should read as "Department of Industrial Engineering and Systems, College of Engineering, Princess Nourah bint Abdulrahman University, Riyadh, 84428, Saudi Arabia". [ABSTRACT FROM AUTHOR]

This review article focuses on the impact of working fluid characteristics, geometrical parameters and the operating coefficients in thermal efficiencies of direct absorption solar collectors (DASCs). Regarding working fluid parameters, the review emphasized the importance of type of base fluid, nanoparticle properties, such as material, size, concentration and shape. Geometrical parameters, including the collector area, aspect ratio, tube diameter and collector panel design, were identified as crucial design considerations for maximizing DASC efficiency. Additionally, the review highlighted the significance of various operating parameters. Solar irradiance was identified as a critical factor, emphasizing the importance of optimizing the collector's orientation and tilt angle to maximize solar exposure. The fluid flow rate within DASCs was also recognized as a key parameter influencing heat transfer and overall performance. Increasing the thermal flow measurement of nanomaterials has been predicted to improve the heat transfer, ultimately leading to improved thermal efficiency. By carefully considering and optimizing these parameters, it is possible to maximize the efficiency and effectiveness of DASCs, thereby advancing the utilization of solar energy for sustainable and renewable power generation. [ABSTRACT FROM AUTHOR]

Phase Change Materials (PCMs) have got widespread attention in thermal energy storage (TES) applications as a result of their wide operational temperature range, high energy storage density, and prolonged life cycle at a reasonable cost. They offer a practical solution to mitigate the building energy consumption, addressing interior temperature fluctuations and enhancing demand-side management through the incorporation of renewable energy and off-peak power. This study focuses on evaluating the influence of PCMs on the performance of radiant heating and cooling systems. Based on conducting a comprehensive review, this study explores the current challenges associated with PCM utilization in these systems. The analysis discloses noteworthy discoveries and potential advantages, paving the way for further investigation and wider adoption of PCMs in the construction industry. Notably, the incorporation of a 10-mm PCM resulted in a 2.4% annual reduction in heating energy consumption in comparison with the existing structures. Furthermore, utilizing a 20–50-mm PCM could yield annual heating energy savings ranging from 7.3 to 15.3%. N-eicosane emerges as the most effective PCM for floor heating, achieving an optimal floor temperature and contributing to a substantial 43% reduction in heating energy consumption. Ultimately, radiant floor systems demonstrate the potential to reduce energy consumption by up to 8% and 4% in a comparison with commercial heating and cooling systems, respectively. [ABSTRACT FROM AUTHOR]