Zeyad Al-Suhaibani

Understanding particles flow behavior is of paramount importance in designing obstructed flow particle heating receivers (OF-PHR), and one of the important metrics is opacity of the particle curtain. In this work, the opacity is defined geometrically, i.e., ratio of area covered by the particles to the total area of the curtain. Particle curtain opacity of an OF-PHR having a single row obstruction was measured. The obstructions tested were perforated plates with two different holes-arrangements, i.e., parallel and staggered. Plate thickness, hole diameter, and pitch were measured to be 1.38, 2.84, and 4.29 mm, respectively, with angles of 60° between three adjacent holes. Two different fall distances (release point) above the obstruction were tested: 30 mm and 60 mm. The tilt angle and mass flow rate used were fixed, i.e., 0° and 1.91 kg/(s∙m), respectively. The opacity was measured across a region for every 20 mm below the obstruction (0-20, 20-40, 40-60, and 60-80 mm); the opacity encompassing the whole region (0-80 mm; overall opacity) was also measured. It was found that the fall distance affects the opacity a little, i.e., doubling the distance from 30 to 60 mm only increased the opacity by 14.4% (relative change) at most. Parallel and staggered hole arrangement resulted in very close values of particle curtain opacity. Finally, it is concluded that to ensure opacity values to remain equal or greater than 85% throughout PHRs with multiple rows downstream, spacing between the perforate plate should be no greater than 40 mm.

Concentrated solar power (CSP) systems offer a promising pathway to reduce fossil fuel dependence, particularly in regions with abundant sunlight. This study evaluates the economic, environmental, and fuel-saving benefits of a CSP system using locally sourced sand as a heat transfer medium. The system integrates a sand–air heat exchanger, a microturbine (100 kWe), and a 300 kW thermal battery. Tested during peak solar hours, the turbine achieved 39.5% thermal efficiency using heliostats to concentrate solar energy and heat sand particles, transferring thermal energy to drive the turbine. Operational data show a 20% reduction in fuel consumption and carbon dioxide emissions, resulting in significant financial reductions and environmental benefits. The thermal battery enables continued operation during cloudy periods or nighttime by storing excess heat, further enhancing fuel efficiency and emission reductions. Reaching technology readiness level 7 in 2018, the prototype demonstrates viability for regions with high direct normal irradiation, such as Saudi Arabia. Key performance factors include heliostat quality, heat exchanger efficiency, and sand thermal properties. Despite challenges like heliostat degradation since 2009, the system shows scalability potential. Solar contribution could reach 80% with an optimized design, amplifying economic and environmental gains. The study highlights the promise of sand-based CSP systems in reducing fossil fuel reliance and supporting global sustainability goals. Future improvements should focus on enhancing heliostat reflectivity, refining heat exchanger design, and selecting sand with better thermal stability. These advancements could pave the way for cost-effective, renewable energy solutions in desert regions rich in solar and sand resources.

The bonded composite repair technique has been widely used to extend the life of cracked structures, such as aircraft and wind turbine structures. After repair, the growth of the crack is significantly slowed until the patch begins to lose its effectiveness. To maintain a low rate of crack growth, the patch repair needs to be replaced once a critical level of adhesion damage (separation) is reached. The objective of this research is to determine the cohesive zone model (CZM) parameters for simulating mode I damage initiation and propagation in different thicknesses of Araldite®2015 structural adhesive. First, mode I load–displacement curves were obtained experimentally using double cantilever beam (DCB) tests. Next, the corresponding fracture toughnesses (GIc) were calculated using the compliance-based beam method (CBBM), which does not require measuring the crack length during testing. Finally, finite element analysis (FEA) was used to predict the progression of adhesion damage using three different softening laws: triangular, trapezoidal, and exponential. The study found that mode I fracture energy is the same for adhesive thickness between 0.20 and 0.30 mm, but then increases by 27% when the adhesive thickness becomes 0.35 mm. Numerically, the results showed good agreement across all softening shapes, with the trapezoidal law being considered the most computationally efficient.

Using solid particulates as a heat transfer medium for concentrated solar power (CSP) systems has many advantages, positioning them as a superior option compared with conventional heat transfer media such as steam, oil, air, and molten salt. However, a critical imperative lies in the comprehensive evaluation of the properties of potential solid particulates intended for utilization under such extreme thermal conditions. This paper undertakes an exhaustive examination of both ambient and high-temperature thermophysical properties of four naturally occurring particulate materials, Riyadh white sand, Riyadh red sand, Saudi olivine sand, and US olivine sand, and one well-known engineered particulate material. The parameters under scrutiny encompass loose bulk density, tapped bulk density, real density, sintering temperature, and thermal conductivity. The results reveal that the theoretical density decreases with the increase in temperature. The bulk density of solid particulates depends strongly on the particulate size distribution, as well as on the compaction. The tapped bulk density was found to be larger than the loose density for all particulates, as expected. The sintering test proved that Riyadh white sand is sintered at the highest temperature and pressure, 1300 °C and 50 MPa, respectively. US olivine sand was solidified at 800 °C and melted at higher temperatures. This proves that US olivine sand is not suitable to be used as a thermal energy storage and heat transfer medium in high-temperature particle-based CSP systems. The experimental results of thermal diffusivity/conductivity reveal that, for all particulates, both properties decrease with the increase in temperature, and results up to 475.5 °C are reported.

New composites made of natural fiber polymers such as wasted date palm surface fiber (DPSF) and pineapple leaf fibers (PALFs) are developed in an attempt to lower the environmental impact worldwide and, at the same time, produce eco-friendly insulation materials. Composite samples of different compositions are obtained using wood adhesive as a binder. Seven samples are prepared: two for the loose natural polymers of PALF and DPSF, two for the composites bound by single materials of PALF and DPSF using wood adhesive as a binder, and three composites of both materials and the binder with different compositions. Sound absorption coefficients (SACs) are obtained for bound and hybrid composite samples for a wide range of frequencies. Flexural moment tests are determined for these composites. A thermogravimetric analysis test (TGA) and the moisture content are obtained for the natural polymers and composites. The results show that the average range of thermal conductivity coefficient is 0.042–0.06 W/(m K), 0.052–0.075 W/(m K), and 0.054–0.07 W/(m K) for the loose fiber polymers, bound composites, and hybrid composites, respectively. The bound composites of DPSF have a very good sound absorption coefficient (>0.5) for almost all frequencies greater than 300 Hz, followed by the hybrid composite ones for frequencies greater than 1000 Hz (SAC > 0.5). The loose fiber polymers of PALF are thermally stable up to 218 °C. Most bound and hybrid composites have a good flexure modulus (6.47–64.16 MPa) and flexure stress (0.43–1.67 Mpa). The loose fiber polymers and bound and hybrid composites have a low moisture content below 4%. These characteristics of the newly developed sustainable and biodegradable fiber polymers and their composites are considered promising thermal insulation and sound absorption materials in replacing synthetic and petrochemical insulation materials in buildings and other engineering applications.

Researchers from all around the world have been paying close attention to particle-based power tower technologies. On the King Saud University campus in the Kingdom of Saudi Arabia, the first integrated gas turbine–solar particle heating hybrid system has been realized. In this study, two different types of experiments were carried out to examine how susceptible prospective liner materials for thermal energy storage tanks were to erosion. An accelerated direct-impact test with high particulate temperature was the first experiment. A low-velocity mass-flow test was the second experiment, and it closely mimicked the flow circumstances in a real thermal energy storage tank. The tests were conducted on bare insulating fire bricks (IFBs) and IFBs coated with Tuffcrete 47, Matrigun 25 ACX, and Tuffcrete 60 M. The latter three lining materials were high-temperature-resilient materials made by Allied Mineral Products Inc. (AMP) (Columbus, OH, USA). The results showed that although IFBs coated with AMP materials worked well in this test, the accelerated direct-impact test significantly reduced the bulk of the bare IFB. As a result, lining substances must be added to the surface of IFBs to increase their strength and protection because they cannot be used in situations where particles directly impact their surface. On the other hand, the findings of the 60 h cold-particle mass-flow test revealed that the IFBs were not significantly eroded. Additionally, it was discovered that the degree of erosion on the samples of bare IFB was unaffected by the height of the particle bed.

Natural convection heat transfer from an inclined array of square cross-section cylinders is experimentally studied. Three cylinders of side length D = 0.02 m and 1 m length are used to form the inclined array. Three-cylinder axis inclination angles to the horizontal of 30°, 45°, and 60° are considered. The cylinders are heated using an internal heating element of constant heat flux. Surface temperatures are measured along the three surfaces of each cylinder; upper, lower, and the front side at nine points spaced evenly by 10 cm. The local circumference average temperature is obtained at each point. Four center-to-center distances to side length S/D = 1.25, 1.75, 2.25, and 2.75 are used. Local Nusselt numbers and the modified Rayleigh numbers are obtained for each cylinder at each circumference averaged temperature point. Results show that the lower cylinder heat transfer is least affected by the array compared to that of its single one followed by the middle and the upper cylinder for all S/D and the inclination angles used. The Nusselt number is degraded from that of the single cylinder at a small S/D and that degradation decreases as the S/D increases for all angles. It is observed that the Nusselt number enhances at the small cylinder axis tilt angle of 30°, followed by 45°, and 60°, especially at high modified Rayleigh numbers. New novel general empirical correlations for Nusselt numbers are obtained for each S/D using the cylinder axis tilt angle, the modified Rayleigh numbers, and the cylinder number in the array as parameters. A new general correlation is obtained for the array using the modified Rayleigh number, S/D, the cylinder axis tilt angle, and the cylinder sequential order number as parameters. These new correlations will help any engineering applications using such a configuration of the array.

Pineapple leaf fiber (PALF), striped sunflower seed fiber (SFSF), and watermelon seed (WMS) are considered natural waste polymer materials, which are biodegradable and sustainable. This study presents new novel thermal insulation and sound absorption materials using such waste as raw materials. PALF, SFSF, and WMS were used as loose, bound, and hybrid samples with different compositions to develop promising thermal insulation and sound-absorbing materials. Eleven sample boards were prepared: three were loose, three were bound, and five were hybrid between PALF with either SFSF or WMS. Wood adhesive was used as a binder for both the bound and hybrid sample boards. Laboratory scale sample boards of size 30 cm × 30 cm with variable thicknesses were prepared. The results show that the average thermal conductivity coefficient for the loose samples at the temperature range 20–80 °C is 0.04694 W/(m.K), 0.05611 W/(m.K), and 0.05976 W/m.K for PALF, SFSF, and WMS, respectively. Those for bound sample boards are 0.06344 W/(m.K), 0.07113 W/(m.K), and 0.08344 W/m.K for PALF, SFSF, and WMS, respectively. The hybrid ones between PALF and SFSF have 0.05921 W/m.K and 0.06845 W/(m.K) for two different compositions. The other hybrid between PALF and WMS has 0.06577 W/(m.K) and 0.07007 for two different compassions. The sound absorption coefficient for most of the bound and hybrid boards is above 0.5 and reaches higher values at some different frequencies. The thermogravimetric analysis for both SFSF and WMS shows that they are thermally stable up to 261 °C and 270 °C, respectively. The three-point bending moment test was also performed to test the mechanical properties of the bound and hybrid sample boards. It should be mentioned that using such waste materials as new sources of thermal insulation and sound absorption materials in buildings and other applications would lead the world to utilize the waste until zero agrowaste is reached, which will lower the environmental impact.

In the present research, AISI P20 mold steel was processed using the milling process. The machining parameters considered in the present work were speed, depth of cut (DoC), and feed (F). The experiments were designed according to an L₂₇ orthogonal array; therefore, a total of 27 experiments were conducted with different settings of machining parameters. The response parameters investigated in the present work were material removal rate (MRR), surface roughness (Ra, Rt, and Rz), power consumption (PC), and temperature (Temp). The machine learning (ML) approach was implemented for the prediction of response parameters, and the corresponding error percentage was investigated between experimental values and predicted values (using the ML approach). The technique for order of preference by similarity to ideal solution (TOPSIS) approach was used to normalize all response parameters and convert them into a single performance index (Pi). An analysis of variance (ANOVA) was conducted using the design of experiments, and the optimized setting of machining parameters was investigated. The optimized settings suggested by the integrated ML–TOPSIS approach were as follows: speed, 150 m/min; DoC, 1 mm; F, 0.06 mm/tooth. The confirmation results using these parameters suggested a close agreement and confirmed the suitability of the proposed approach in the parametric evaluation of a milling machine while processing P20 mold steel. It was found that the maximum percentage error between the predicted and experimental values using the proposed approach was 3.43%.

The present research used the stir-casting method to develop an Al-based composite. The developed composite exhibited challenges while being processed on conventional machining. Thus, a non-traditional machining process was opted to process the composite. The machining variables selected for the current research were the pulse off time (Toff), pulse on time (Ton), servo voltage (SV), current (I), and tool electrode. Three tool electrodes (SS-304, copper, and brass) were used to process the developed composite (Al/SiC/Gr). The experimental plan was designed using response surface methodology (RSM). The output responses recorded for the analysis were the material removal rate (MRR) and tool wear rate (TWR). The obtained data was optimized using complex proportional assessment (COPRAS) and machine learning methods. The optimized settings predicted by the RSM–COPRAS method were Ton: 60 µs; Toff: 60 µs; SV: 7 V; I: 12 A; and tool: brass. The maximum MRR and TWR at the suggested settings were 1.11 g/s and 0.0114 g/s, respectively. A morphological investigation of the machined surface and tool surface was conducted with scanning electron microscopy. The morphological examination of the surface (machined) presented the presence of cracks, lumps, etc.