Effects of Refining Parameters on the Properties of Oil Palm Frond (OPF) Fiber for Medium Density Fibreboard (MDF)

Studies on the manufacture of medium density fiberboard (MDF) from oil palm frond (OPF) fibre were conducted to provide a sustainable and feasible source of lignocellulosic materials. The quality and properties of the fibre are very important as it dictates the final MDF properties. The properties of fibre like fibre pH, buffering capacity, and morphology can influence most of the MDF performances. Refining condition is one of the most important factors which determine the properties of the refined fibre. In this study, the effects of different refining pressures and temperatures on OPF fibre were evaluated. The refining of OPF fibre was observed at four levels of refining parameters; which were categorized as low (2 bar at 130 °C), medium (4 bar at 150 °C), high (6 bar at 170 °C), and severe (8 bar at 190 °C). The refining heating time of 5 minutes was employed. The pH, buffering capacity, morphology, and the surface of the fibres were evaluated. The refined fibres were used to manufacture fibreboard panels at a target density of 720 kg/m3 and 12% urea formaldehyde (UF) resin. The panel's physical (thickness swelling) and mechanical properties (bending and internal bonding strength) were then evaluated according to European Standard (EN 622-5, 2006). The results indicated that refining conditions affected the properties of the fibres and final boards. High steam pressure and temperature-induced pH changes in OPF fibres, leading to more acidic fibres and greater acid buffering capacity. The fibre separation was more adequate at this level and produced fibre with a smooth surface. Based on the test results for fibreboard properties, high steam pressure and temperature produced better dimensional stability of panels and bending and bonding strength. However, at the highest refining condition (severe level), the board performances began to deteriorate. The best performances of the samples were found for the panels made under refining conditions of 6 bar at 170 °C.

A Stress Mapping Immersed Boundary Method for Viscous Flows

This work introduces an immersed boundary method for two-dimensional simulation of incompressible Navier-Stokes equations. The method uses flow field mapping on the immersed boundary and performs a contour integration to calculate immersed boundary forces. This takes into account the relative location of the immersed boundary inside the background grid elements by using inverse distance weights, and also considers the curvature of the immersed boundary edges. The governing equations of the fluid mechanics are solved using a Galerkin-Least squares finite element formulation. The model is validated against a stationary and a vertically oscillating circular cylinder in a cross flow. The results of the model show acceptable accuracy when compared to experimental and numerical results.

Void and Moisture Content of Fiber Reinforced Composites

In this paper, a short review on the void and moisture content studies of fiber reinforced composites for both, synthetic and natural based fibers are presented. The review summarized the research papers in which include experimental and theoretical works that related to the void and moisture content studies. In addition to that, this review paper highlighting a few research studies conducted in literature on the effects of the void and moisture on the mechanical performances of the composite. Few common measurement methods used for the void and moisture determination are discussed here. The aims of this short review, mainly to capture the trend ranging from the recent five years back and summarize the various studies and also to compare and conclude the most common method for the determination of the void and moisture content. This paper is mainly providing a baseline in the selection of the methods for the future work of the author’s work with regard to the reduction of the presence of voids and moisture occur during the impregnation process of fiber reinforced composites, especially when using natural-based fiber.

Flow Past a Fixed and Freely Vibrating Drilling Riser System with Auxiliaries in Laminar Flow

Drilling risers used in oil and gas operations are subjected to external loads such as wave and current. One of the phenomena that arise from the external loads is the Vortex-Induced Vibration (VIV), which affects the performance of the riser due to excessive vibration from the vortex shedding. A significant factor influencing the VIV is the design of the drilling riser and its auxiliary lines. Until now, the optimum geometrical size and gap between the auxiliary and the main riser are still very scarcely studied. In this paper, the main objective is to study the effects of the gap ratio (G/D) on the vortex shedding phenomenon on a fixed and freely vibrating riser. The riser system was modelled with a main drilling riser and six auxiliary lines with a constant diameter ratio (d/D) of 0.45 and gap ratio (G/D) = 0 to 2.0 in the laminar flow regime with Reynold Number, Re = 200. The simulations were conducted for Single Degree of Freedom (SDOF) using Computational Fluid Dynamics (CFD) software, Altair AcuSolve. It was found that the freely vibrating riser experienced higher lift and drag forces as compared to the fixed riser due to the synchronization (lock-in) of the shedding vibration and the natural frequencies. The lock-in phenomenon is normally observed on the drilling riser at different current directions. The forces are reduced when G/D is higher. The vortex shedding was significantly reduced for auxiliaries between 0.3 to 1.4. It is confirmed that by modifying the interaction of the vortices in the wake region with auxiliary lines, the hydrodynamic forces will be decreased. Finally, this fundamental study could potentially be used in the designing stage of an optimum drilling riser system by considering significant governing factors.

Dual Solutions in Mixed Convection Flow Along Non-Isothermal Inclined Cylinder Containing Gyrotactic Microorganism

The purpose of this research is to present dual solution for combined free and forced convection flow towards a non-isothermal permeable inclined cylinder containing gyrotactic microorganism. Though several researches were done on dual solutions for mixed convection and also along the vertical cylinder for the numerous engineering applications but very few works have done on dual solutions for mixed convection with gyrotactic microorganisms. Two steps are performed here to carry out numerical calculations. Firstly, the governing partial differential equations are simplified into set of coupled non-linear ordinary differential equations using similarity transformations and then solved numerically using bvp4c function from MATLAB. Dual solutions are observed for heat, mass and density of motile microorganism transfer rate and also for velocity, temperature, concentration, and microorganism profile beyond a critical point. The research is reached to excellent argument by comparison in few cases between the results obtained from MATLAB and Maple algorithm. The heat, mass and motile microorganism transfer rate decreases from free to mixed convection regime and then increases to forced convection regime with the influence of different flow control parameters. The results also indicate that dual solutions for different flow profiles exist only in free convection dominated regime.

Effect of Different Types of Stenosis on Generalized Power Law Model of Blood Flow in a Bifurcated Artery

This study is focus on generalized power law model of blood flow in a stenosed bifurcated artery under the effect of different types of stenosis. Stenosis can cause the narrowing of the artery that may reduce the flow of blood supply to the heart, and this may lead to the heart attacks. The geometry of the bifurcated artery with different classification of stenosis locations is considered in order to shows four possible morphologies formation of plaque from healthy artery to disease artery. The bifurcated artery is modelled as a two-dimensional rigid wall since the wall of a disease artery is reported to be less flexibility. Few assumptions are considered such as blood are incompressible, laminar, steady and characterized as the generalized power-law model. Simulation results are obtained using COMSOL Multiphysics 5.2, which is a software that based on the finite element method to solve this problem. Results concerning the effect of different locations of stenosis on generalized power law model of the blood flow characteristic such as streamlines pattern are discussed.

Effect of Mesh Type on Numerical Computation of Aerodynamic Coefficients of NACA 0012 Airfoil

Mesh type and quality play a significant role in the accuracy and stability of the numerical computation. A computational method for two-dimensional subsonic flow over NACA 0012 airfoil at angles of attack from 0o to 10o and operating Reynolds number of 6×106 is presented with structured and unstructured meshes. Steady-state governing equations of continuity and momentum conservation are solved and combined with k-v shear stress transport (SST-omega) turbulence model to obtain the flow. The effect of structured and unstructured mesh types on lift and drag coefficients are illustrated. Calculations are done for constant velocity and a range of angles of attack using Ansys Fluent CFD software. The results are validated through a comparison of the predictions and experimental measurements for the selected airfoil. The calculations showed that the structured mesh results are closer to experimental data for this airfoil and under studied operating conditions.

A Numerical Prediction of Stabilized Turbulent Partially Premixed Flames Using Ammonia/Hydrogen Mixture

The objective of this work is to computationally assess the performance of a carbon free ammonia-hydrogen mixture when burnt in a gas turbine like combustor. Recently, utilizing ammonia as an alternative carbon-free fuel for future power, industry applications and achieving clean energy attracted enormous interest. Pure ammonia oxidation is facing many challenges such as high NOx emissions, high ignition energy, slow reactivity and lower laminar flame speeds. Therefore, the use of ammonia/hydrogen mixture provides flame stability and increasing flame speed. In this manuscript a numerical study for a new swirl stabilized combustor for oxidizing ammonia/hydrogen mixture. Numerical two dimensional model simulations of a turbulent flame on Reynolds Averaged Navier Stokes (RANS) including a realizable k-e turbulent scheme with the aid of chemistry mechanism were performed under various conditions. Partially premixed combustion model with flame-let concept was selected and radiation effects are also considered. Validation for the predicted results showed a reasonable agreement when validated with the experimental data. The results discuss the influence of changing inlet pressure and equivalence ratio on the stability and the characteristics of unburnt NH3 and NO emissions. Results show that for constant operating conditions such as constant equivalence ratio of 0.8 that increasing hydrogen content resulted in increasing NO emission. Also, for constant ammonia/hydrogen concentrations, NO emissions increases with equivalence ratio then reduced at rich conditions and NH3 emissions are generally low. Equivalence ratio lower than 1.2 will be preferable to reduce the amount of unburnt NH3 formation.

Experimental Investigation on Evacuated Tube Solar Collector Using Biofluid as Heat Transfer Fluid

Bio-oil extracted from waste of different plant kernel was used as heat transfer fluid in evacuated tube solar collector. Thermal performance of the biofluids to the enhancement of the evacuated tube solar collector under varying weather conditions and experimental analysis was carried-out. Thermal analysis on the storage water tank temperature, outlet and inlet heat transfer fluid temperature, and heat gains by was studied. In addition, the biofluids thermophysical properties and degradation analysis was conducted and compared with conventional base-fluids. From the results the biofluids caused enhancement of heat gain in the collector receiver by 9.5%, 6.4% and 3.2% for moringa oleifera kernel oil (MOKO), date kernel oil (DKO) and palm kernel oil (PKO), respectively. The storage water tank temperature at night fall was 53, 49, 51 and 47oC, for the MOKO, DKO, PKO and water HTFs, respectively. The biofluids were thermal stable and with no degradation. The biofluids demonstrated potentials as heat transfer fluids in thermal applications but there are needs for more investigations on their enhancement with organically synthesized nano particles to preserve there no corrosive and toxicity nature, and experimental performance on heat exchangers after several heating cycles.

Study On the Potentiality of Power Generation from Exhaust Air Energy Recovery Wind Turbine: A Review

Presently the worldwide lockdown from Covid-19 give a huge effect on different sectors across the board, notably on energy consumption. Lockdowns have fuelled the intensification of low-carbon resources in terms of electricity production, yet a drastic upswing in electricity use in residential districts during the pandemic. By exploring economic renewable energy resources, the world is trying to overcome the crisis and one of them is wind energy, where this sustainable energy system is highly demanded, thus reducing global CO2 emissions. Researchers have carried out several findings on wind energy obtained from wind turbines at various potential locations, but most of it used natural sources as a wind stream. Therefore, a revolutionary concept on extracting clean energy from manufactured wind resources with wind turbine system for power generation is introduced in recent studies. The main goal of this review paper is to emphasize the performances of power generation through Exhaust Air Energy Recovery Wind Turbine. The potentiality of wind extractions is reviewed to achieve the clear overview of this new progressive ideas and the important configurations is accentuated. Most findings indicated that this energy recovery device converts wasted energy to a more profitable form by converting it to electricity, resulting in a rapid return on investment. Moreover, the enclosing the output area of wind turbines for recovering energy enhances overall efficiency.