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This research examines the hybrid nanofluid alumina-copper/water flow over a permeable sheet, considering slip, magnetohydrodynamics, and heat source. To analyze the system, the model is transformed into nonlinear ordinary differential equations (ODEs) via the similarity transformation. Numerical solutions are attained through the implementation of the bvp4c function in MATLAB. The study analyzes velocity and temperature profiles, local skin friction, and Nusselt number for various parameters. Moreover, the impact of magnetohydrodynamics on the system is explored. Increasing the magnetic parameter leads to an enlargement of the boundary layer thickness and an elevation in the skin friction coefficient. Overall, this study sheds light on the complex behavior of hybrid nanofluid flows and provides valuable insights into the effects of slip, magnetohydrodynamics, and heat source on the model while also presenting a validated model showcasing the compelling enhancement of heat transfer through the incorporation of copper into alumina nanofluid.

The foremost objective of this study is to reflect the behaviour of hybrid nanofluid towards a permeable porous medium, with consideration of second-order velocity slip and heat absorption impacts on the fluid flow. Two distinct fluids of copper (Cu) and aluminium oxide (Al2O3) are reviewed in this study to work out as a hybrid nanofluid flow. The equations of boundary layer flow in the form of partial differential equations are reduced to a system of ODEs by conducting a similarity transformation technique, and the findings that obtained from this study are presented in the respective tables and figures. The effects of involving parameters such as suction, porous medium permeability, heat absorption and second order velocity slip are perceived, as well as our intention in observing the impact of traditional nanofluid and hybrid nanofluid on the fluid flow. Our findings revealed that the hybrid Cu-Al2O3/water nanofluid performs well on the fluid flow behaviour against the mono Al2O3/water nanofluid. Moreover, the participating parameters of porous medium permeability, suction and nanoparticle volume fraction are said to improve the boundary layer thickness, while second-order velocity slip parameter is deemed to decay the fluid flow.

Studies of hybrid nanofluids flowing over various physical geometries and conditions are popular among researchers to understand the behavior of these fluids. Thenceforth, the numerical solutions for hybrid Ag-CuO/H2O nanofluid flow over a stretching sheet with suction, magnetic field, double stratification, and multiple slips effects are analyzed in the present study. Governing equations and boundary conditions are introduced to describe the flow problem. Then, similarity variables are applied to transform the equations into non-linear ordinary differential equations and boundary conditions. The numerical computation for the problem is done in Matlab (bvp4c solver), and the results are presented in tables and graphs. It is found that the rise in solutal slip and stratification parameters reduces the Sherwood number. Meanwhile, the increase in thermal slip and stratification parameters lowers the Nusselt number. The skin friction coefficient is observed to increase with the augmentation of the hydrodynamic slip parameter.

This paper investigates the influence of suction on the flow, heat and mass transfer characteristics over a permeable shrinking sheet immersed in a doubly stratified micropolar fluid. The model which consists of partial differential equations is converted into a set of nonlinear equations using similarity transformations and then solved using the bvp4c solver. Numerical results obtained are presented graphically for the distributions of velocity, angular velocity, temperature and concentration profiles within the boundary layer for various values of the magnetic parameter and wall mass suction parameter. It is visualized that the enhancement of suction parameter will increase the skin friction, heat transfer rate (local Nusselt number) and Sherwood number. It is also found that as the magnetic parameter increase, there is an increment in the skin friction while opposite results are obtained for the local Nusselt number and Sherwood number.

This study investigates the multi-objective optimization of reaction parameters with response surface methodology (RSM) with central composite design (CCD) for the deoxygenation of waste cooking oil (WCO) over low cost-modified local carbonate mineral catalyst (NiO-Malaysian dolomite) into green fuel in the range of gasoline, kerosene and diesel. RSM was performed to study the effect of four operating parameters: temperature (390–430 °C), time (30–120 min), catalyst loading (1–10 wt%) and nitrogen flow rate (50–300 cm3/min). The results indicate that for maximum WCO conversion, deoxygenated oil and product yield, the optimum parameters of the deoxygenation reaction were at 410 °C, 60 min, 5.50 wt% of catalyst loading, and 175 cm3/min of N2. The green fuel properties testing (density, kinematic viscosity, flash point, cloud point, pour point, sulfur, carbon residue, cetane index, oxidation stability, acid value, iodine value and calorific value) and GC–MS analysis show that the product oil meets almost all the requirements of green diesel fuel and hydrocarbon biofuel standards for fuel application while the quadratic model proposed agreed with the experimental data (95% confidence) which indicates that the RSM can adequately predict the reaction products.

Magnetic nanofluids (MNFs) have been the focus of extensive research nowadays owing to their potential usefulness as a transfer medium. This study is concerned with the boundary layer flow and heat transfer of MNF past a rotating vertical cone with the embedment of the porosity regime and mixed convection. The buoyancy opposing flow on the combined free and forced convection is being emphasized in this study to evaluate the behavior of the fluid within this region and predict the point of the boundary layer transition. The initial formulation of the model is simplified appropriately by employing the suitable similarity transformation. The package of bvp4c MATLAB is employed to execute the numerical solutions. Analysis of stability is also reported. Due to the mixed convection parameter, the opposing flow contributes towards two different alternative solutions, but the second solution is not stable. A higher local Nusselt number are achieved by increasing the concentration of magnetic nanofluid up to 2% and enlarging the mixed convection parameter under the influence of the porosity regime in the vertical rotating cone. It has been established in this study that the addition of cobalt ferrite as the magnetic nanoparticles (MNPs) is proven to have the ability in enhancing the thermal performance of the fluid.

In this work, the comparative study on the performance of K2O/SiO2 and calcined dolomite catalysts was conducted via deoxygenation of waste cooking oil (WCO). KSi catalyst has the potential as a deoxygenation catalyst due to mesoporous structure catalyst with high base properties which enhance oxygen removal. The result found that K2O/SiO2 catalyst could be used in the deoxygenation of WCO generating a high yield of pyrolysis oil as compared to thermal deoxygenation and calcined dolomite catalyst. Besides that, the reusability and regeneration of the K2O/SiO2 catalyst were evaluated in the deoxygenation reaction using WCO as a feedstock. Five consecutive runs of reusability test and three successive cycles with two regenerations were performed. The reusability and followed by regeneration tests were conducted at conditions: 30 min of reaction time, 390 ± 5 °C reaction temperature and 150 cm3/min of N2 flow rate. The liquid products obtained from each cycle were analyzed by GC–MS. The deoxygenation of WCO using K2O/SiO2 catalyst rendered higher selectivity towards diesel products (C13-C24). The K2O/SiO2 catalyst presented a good performance in reusability and regenerability test with only ∼19.3–22.4% dropped in pyrolysis oil yield after 5 consecutive runs and only ∼11.20–13.23% drop in diesel yield after regeneration. The results showed that K2O/SiO2 catalyst has tremendous stability in the deoxygenation of WCO into green diesel and could be the alternative deoxygenation base catalyst for the deoxygenation process.

Co-pyrolysis is one of the best new technologies to utilise excess of plastic waste where the products are generated in the form of oil, gas and char. A selective catalyst is needed to improve the quality of the co-pyrolysis product, in which, oil with low of oxygenated compounds content and high yield of oil are favoured. In this work, Malaysian dolomite was modified by doping with transition metals (Ni/Fe/Ca) at 10 wt% loading using the precipitation method and then compared with a modified commercial catalyst named NiO/ZSM-5 zeolite. Co-pyrolysis was conducted using empty fruit bunch (EFB) and high-density polyethylene (HDPE) at 500 °C operating temperature, 10 cm3/min N2 flow rate, 10 wt% catalyst loading, 1:3 HDPE:EFB ratio and 75 g of feedstock with 60 min of operating time in a stainless-steel fluidised bed reactor. The catalysts were characterised using different analysis methods such as XRD, BET and SEM. The highest gas yield of 68% was obtained by increasing the content of calcium oxide (CaO) in dolomite (in dolomite (CaO/CMD900). For the Fe-doped dolomite (Fe3O4/CMD900), the highest oil yield (10.34 wt%) and a high content oxygenated compounds were obtained. For the Ni-doped dolomite (NiO/CMD900), the oil with the highest hydrocarbon yield (85.32 %) and low oxygenated compound (14.68 %) was obtained. This study confirms that modified dolomite can increase the yield and quality of bio-oil.

Structural, thermal and optical properties of lead-tellurite oxide glasses consisting TeO2 – PbO – Bi2O3 – Er2O3, synthesized by high temperature melt-quenching-thermal annealing method were investigated in this study. The role of rare-earth element, erbium ion as dopant into the host glass has affected physically, thermally and optically of the glasses. The amorphous nature of the glasses was confirmed by XRD (x-ray diffraction). Thermal exo-endothermic event profiles clarify its glass transformation temperature Tg, crystallization temperature Tx, and melting temperature Tm are exist. Both UV-Vis-NIR optical absorption and Raman spectroscopy have revealed optical energy gap changes due to the structural deformation by the erbium ions. Related obtained glass parameters such as polarizability, refractive indices and metallization criterion were also explained further in this study.

Mixed convection is commonly used in electronic cooling processes and nuclear reactor technology. As a result, this study aims to demonstrate the mathematical formulation of fluid flow, heat and mass transfer under the controlling physical parameters such as mixed convection, buoyancy ratio, suction, magnetic field, and rotation angle of the sheet. The variation in the wall shrinking velocity, temperature and concentration is expressed as an exponential function. Since controlling equations are partial differential equations, similarity transformations convert these partial differential equations to ordinary differential equations. Finally, these ordinary differential equations are considered as a non-linear and non-dimensional boundary value problem. The final solution of these ordinary differential equations is obtained numerically by applying the Matlab bvp4c programme. Stability analysis which determines the most stable numerical solution between duel solutions is also made using the Matlab bvp4c programme. Comparing the obtained computational results to previously published data shows a good agreement. All numerical results are graphically illustrated and explained, including the velocity, temperature and concentration profiles, skin friction coefficient, local Nusselt number, and local Sherwood number. Tables 2, Figs 7, Refs 41.