Effect Of Inclination Angle Research Articles

Optimisation Studies on Performance Enhancement of Spray Cooling - Machine Learning Approach

The performance optimisation of spray cooling heat transfer systems has been identified as a significant step in improving process efficiency, and the application of machine learning tools is a recent development that has enhanced this. This study aims to maximise the heat transfer coefficient for spray cooling at low heat flux levels. The effects of nozzle inclination angle, water pressure, and spray height on heat transfer coefficient were studied. Taguchi L27 orthogonal array technique was used to perform the experiments. A maximum heat transfer coefficient of 181.4 kW/m2K was obtained at a nozzle inclination angle of 60o, spray height of 4 cm, and water pressure of 15 psi. Analysis of variance was performed to find the significance of each variable and its interactions. The results show that for the maximum heat transfer coefficient (181.4 kW/m2K), the optimum levels of the independent variables were A3H1P3, i.e., the highest level of nozzle inclination angle (60o), the lowest level of spray height (4 cm), and the highest level of water pressure (15 psi). The support vector machine outperformed the Random Forest algorithm and Multiple Regression analysis regarding prediction accuracy with a maximum error of 0.15% and root mean squared error of 0.01.

Optimizing Heat Transfer in Heat Pipes Using Hybrid Nanofluids With Multi‐Walled Carbon Nanotubes and Alumina

ABSTRACTThis study investigates the thermal performance of heat pipes using hybrid nanofluids composed of multi‐walled carbon nanotubes (MWCNT) and aluminum oxide (Al2O3) nanoparticles. The aim was to assess the effects of nanoparticle concentration (0.1%–0.5%), filling ratio (60%–90%), heat input (50–80 W), and inclination angle (0°–90°) on thermal resistance and heat transfer coefficient (HTC). Hybrid nanofluids were prepared using ultrasonic homogenization, and their stability was confirmed by zeta potential analysis, showing a reduction from −60 to −48 mV over 30 days. Experimental results revealed that the thermal resistance decreased with increasing filling ratio and inclination angle, reaching a minimum of 0.80 K/W at a 90° angle, 90% filling ratio, and 80 W heat input. Similarly, the overall HTC increased with these parameters, peaking at 2250 W/m2 K under the same conditions. At a 0.5% nanoparticle concentration, the HTC improved by up to 40% compared with conventional fluids. The thermal conductivity of the hybrid nanofluid also rose significantly, from 0.7 W/m K at 30°C to 1.5 W/m K at 90°C, outperforming distilled water. These findings highlight the potential of hybrid nanofluids to enhance heat pipe efficiency, particularly in high‐power applications, by optimizing nanoparticle concentration, filling ratio, and inclination angle.

Thermal Performance Investigation of Vapor Chamber Under Partial Heating and Different Heat Flux Conditions: Effects of Inclination Angle

Abstract The need for cooling technologies increases tremendously with raising demand on the powerful and compact electronics. There, it pushes the research and technology to the new investigations on varying heat transfer mechanisms and devices. While one of these devices is vapor chamber (VC), an experimental study has been carried out to investigate the heat transfer performance of a VC under partial heating, varying heat fluxes, and different inclination angles for different temperatures, in the current study. For this purpose, a VC with a dimension of 90 mm × 90 mm × 3 mm is evaluated via its resulting thermal resistance, performance, and the temperature distribution over the VC surface. There, the limited effect of inclination angle is observed on the performance, while the highest change is obtained with decreasing local heating surface area, thus increasing heat fluxes. Moreover, this trend is seen almost similar with a reasonable shift up or down according to the different temperature differences.

Vegetation monitoring in mining area using canopy reflectance and landsat8 oli image

The aim of this study is to find out the vegetation monitoring in mining areas which is of great significance in grasping the ecological environment status of mining areas. As the first target of spectral reflection, the vegetation canopy directly affects the results of spectral reception. Leaf Angle Distribution (LAD) is a key canopy structural parameter, which directly determines the amount of solar radiation intercepted by the canopy. Taking the relationship between the effect of leaf inclination angle on vegetation canopy reflectance and NDVI as an entry point, the study monitored and analyzed the vegetation in Dexing mining area, China, from 2013 to 2018 by NDVI, based on which the Copper Stress Vegetation Index (CSVI), which is applicable to the narrow wavelength band of remote sensing imagery, was evaluated whether it could be applied to the wide wavelength band. The results show that the NDVI value of the horizontal distribution is significantly higher than that of other leaf inclination distributions, and the NDVI in the direction of the horizontal distribution is 0.82, while the NDVI in the direction of the hi-straight distribution is 0.75; the NDVI of the mining area decreases gradually with the increase of the area of the mining area, and the correlation coefficients of the two groups of CSVI based on the wide and narrow bands are not large, which is not suitable for the vegetation monitoring by using the Landsat8 OLI imagery. Wide band is less applicable for vegetation monitoring. Bangladesh J. Bot. 53(3): 835-847, 2024 (September) Special

Cracking evolution and failure mechanism of brittle rocks containing pre-existing flaws under compression-dominating stresses: Insight from numerical approach

Comprehending the cracking evolution and failure mechanism of flawed rocks under compression-dominating stresses is essential to evaluating the stability of rock engineering. In this work, a newly developed geometry-constraint-based non-ordinary state-based peridynamic (GC-NOSBPD) theory that can eliminate the numerical oscillation is applied to predict the development of new cracks of flawed rocks under compression-dominating stresses. The failure of bonds between particles is judged by the bond-associated stress-based fracture criteria. The cracking evolution trajectories of semi-disc and disc specimens containing flaws are traced. The effects of flaw inclination angle on the cracking trajectories are analyzed. The cracking evolution paths of rock-like specimens with two flaws under uniaxial and biaxial compression are molded. The effects of confining stress on the growth of new cracks are investigated. The confining stress restrains the propagation of tensile cracks, but it is easy to promote the growth of shear cracks. The concentration and transfer effects of stress can plainly revel the failure mechanism of flawed rocks. The present numerical method is reasonable to predict the tensile and shear failure modes of flawed specimens under compression-dominating stresses.

Effect of small inclination angle on heat transfer performance of Ω-grooved bending heat pipe

Grooved bending heat pipe may operate at small inclination angle caused by practical installation errors. Previous researches mainly focused on large inclination angles of straight heat pipes, but fewer experiments were conducted at small inclination angle of bending heat pipe where liquid accumulation and gravity effect on liquid-vapor transport varies along the pipe. This paper experimentally studied the effect of small inclination angle (±3°) on heat transfer of aluminum-ammonia Ω-grooved bending heat pipe with total length of 650mm, vapor chamber diameter of 4mm and grooved wick diameter of 1.24mm. The results showed that small inclination angle significantly affect the heat transfer performance of bending heat pipe with heat transfer limit changed by 9 times form 20W to 180W and thermal resistance changed by 8 times from 0.04 K/W to 0.32 K/W. Effect of negative and positive angles in bending heat pipe is complex than that in straight heat pipe. Positive condensation end inclination enhances heat transfer due to gravity-driven liquid reflux. Negative condensation end inclination inhibits heat transfer due to anti-gravity reflux and liquid accumulation suppressing gas condensation. Positive evaporation end inclination weakens heat transfer due to anti-gravity reflux. Negative evaporation end inclination also weakens heat transfer due to thick liquid film, increasing thermal resistance and potentially blocking vapor channels. Attributed to coupling effect of liquid accumulation at bending section and capillary force dominant at tiny incline, maximum heat transfer limit of 180 W is achieved at both end inclination of -0.5°.

The field-enriched finite element method with gravity effects for simulating the cracking behaviors of large-scale engineering rock masses

The field-enriched finite element method uses a scalar field defined as a field variable to describe cracks and characterize their impact on the displacement field and stress field of the solution model. It is capable of avoiding remeshing and employing level set functions to describe cracks when simulating the propagation of cracks. In this work, a field-enriched finite element model with gravity effects is proposed to simulate the large-scale failure process of engineering rock masses, and several numerical cases of geotechnical engineering are successfully analyzed. First, by introducing the unified tensile fracture criterion into the numerical model, the large-scale failure process of the intact slope is simulated. Second, the sliding process of rock slopes containing en echelon joints is numerically investigated. Third, the cracking process of the concrete dam is analyzed. Finally, the effects of joint and bedding plane inclination angles on the stability of tunnel chamber in transversely isotropic rock mass are studied. The numerical results indicate that the numerical method proposed in this work can accurately solve the large-scale failure process of rock masses.

Experimental study on the mechanical properties of red sandstone with fractures under different loading rates

In order to study the effects of crack inclination angle and loading rate on rock mechanical properties, creep characteristics, and failure characteristics. Taking homogeneous red sandstone with different fracture angles as the research object, uniaxial compression tests and uniaxial compression creep tests were conducted at different loading rates. The results showed that under the same fracture angle, the loading rate was positively correlated with the peak strength, elastic modulus, instantaneous strain, creep strain, and steady-state creep rate of the sample, while negatively correlated with the peak strain. At the same loading rate, the mechanical properties and creep properties of the sample were controlled by the crack inclination angle α. With the increase of α, the peak strength, peak strain, instantaneous strain, creep strain and steady-state creep rate decreased first and then increased, and the elastic modulus increased. On the basis of rock creep testing, it is also important to establish a creep model that conforms to the actual test situation for studying rock creep characteristics. However, many models currently used cannot accurately describe the three stages of rock creep, especially the accelerated creep stage. Therefore, based on Burgers elements, this paper introduces plastic damage bodies based on damage rates and software components based on fractional calculus, A new creep model was obtained and its rationality was verified through experimental results. The results showed that the fit between the model and experimental data was above 0.97, indicating that the model can better describe the three stages of rock creep, especially reflecting the non-linear characteristics of the accelerated creep stage.

Empirical Predictions on Wave Overtopping for Overtopping Wave Energy Converters: A Systematic Review

Over the past three decades, the development and testing of various overtopping wave energy converters (OWECs) have highlighted the importance of accurate wave run-up and overtopping predictions on those devices. This study systematically reviews the empirical formulas traditionally used for predicting overtopping across different types of breakwaters by assessing their strengths, limitations, and applicability to OWECs. This provides a foundation for future research and development in OWECs. Key findings reveal that empirical formulas for conventional breakwaters can be categorized as mild or steep slopes and vertical structures based on the angle of the slope. For the same relative crest freeboards, the dimensionless average overtopping discharge of mild slopes is larger than that of vertical structures. However, the formula features predictions within a similar range for small relative crest freeboards. The empirical formulas for predicting overtopping in fixed and floating OWECs are modified from the predictors developed for conventional breakwaters with smooth, impermeable and linear slopes. Different correction coefficients are introduced to account for the effects of limited draft, inclination angle, and low relative freeboard. The empirical models for floating OWECs, particularly the Wave Dragon model, have been refined through prototype testing to account for the unique 3D structural reflector’s influence and dynamic wave interactions.

Effect of Inclination Angle on Wall Shear Stress in Upward Two-Phase Flow in a Pipe

Effect of Inclination Angle on Wall Shear Stress in Upward Two-Phase Flow in a Pipe

Performance evaluation of self-propelled rotary tools and fixed round inserts in machining

This study evaluates the analysis of round inserts (Fixed and Self-Propelled Rotary Tools) when machining hardened steel. Self-propelled rotary Tools (SPRTs) exploit the entire perimeter of the insert rather than a specific cutting edge, minimizing insert wear and maximizing insert life. It is considered an environmentally friendly process. Tool and insert geometry have a direct effect on the surface roughness. Previous studies highlighted the significant effects of one inclination angle on surface roughness. Despite previous research that investigated only one inclination angle, in this research, the effect of both inclination angles has been investigated, and a new method for simultaneous application has been used. The optimal use of both inclination angles has significantly improved the quality of the machined surface. Therefore, an optimal holder has been designed and fabricated based on the cutting forces and component shapes, allowing inclination angle changes. The full factorial design of the experiment is adopted, and the effects of the horizontal and vertical inclination angles and feed rate in fixed tool and SPRT turning have been evaluated, each in 3 levels with a total of 54 experiments. The equivalent insert radius is defined using the inclination angles and an analytical model is developed concerning the equivalent insert radius to predict surface roughness. The proposed model accurately estimated roughness in fixed tool turning for an R-square of 0.81 and 0.76 for SPRT turning. In the best condition, the surface roughness has been measured at 0.472 μm in the fixed tool turning and 0.409 μm in SPRT turning.

Numerical study and experimental validation of a porous biochar supported form stable composite for thermal energy storage

This study numerically investigates the performance of the melting process for a biochar-based phase change material latent heat energy storage system. The melting processes of a composite made from softwood biochar combined with paraffin RT28, were compared numerically using the equilibrium porous medium model in ANSYS Fluent. The set up was validated through results from previous literature and experimental work. The enhancement in melting was compared to the pure PCM melting scenario and the effects of different paraffins, boundary conditions and inclination angle were investigated for real world application. Softwood biochar composites significantly surpass the performance of paraffin alone, reducing the melting time by 79 %. Different paraffins within the softwood composite produced different melting times, ranging from 2565 s to 4790 s. In terms of inclination angle adjusting to 90° produced steadier heating and reduced the melting time by 63 % in the composite. These findings offer insights into optimising latent heat thermal energy storage systems for improved performance and reduced energy wastage, highlighting the potential of biochar composites in sustainable energy solutions.

Numerical study on the effects of tube inclination angle and heat conductive cover plate on freeze plug performance in molten salt reactors

The freeze plug is an important passive safety system used in the molten salt reactors (MSRs). However, although the inclination angle is one of the fundamental design parameters, its influence on the freeze plug performance has not been explored systematically. Multidimensional numerical simulations were hence carried out to analyze the effects of tube inclination on the solidification and melting processes of salt encountered in the freeze plugs of the MSRs in this work. The effects of placing a high thermal conductivity cover plate on the outer wall of the freeze plug were also investigated. In the solidification process, the tube inclination had a significant impact on the equilibrium shape of the frozen salt. A decrease in the inclination angle from the horizontal resulted in a reduction in the plug volume, and closing of the freeze plug became more difficult when the inclination angle was small and the tube diameter was large. In the melting process, natural convection induced in the liquid salt was intensified with a decrease in the inclination angle. This accelerated the melting of solid salt to shorten the opening time significantly. Optimizing the tube inclination angle was hence shown to be of great importance to improve the safety of MSRs. When a copper plate was placed on the freeze plug outer wall to facilitate the heat transfer to the frozen salt, its influence on the solidification process was not noticeable, while melting was accelerated and the opening time was reduced by about 20%.

Pullout behavior of polyethylene fiber from cement matrix: Effect of embedment length, matrix strength, and inclination angle

Engineered cementitious composites reinforced with polyethylene fibers (PE-ECC) exhibit the potential for high strength and toughness. To optimize the performance and tailor the properties of PE-ECC, this study focuses on analyzing the pullout behavior of polyethylene (PE) fibers from matrices through single fiber pullout tests and scanning electron microscopy analysis. One fiber type was used throughout the experiment, while three embedment lengths and three inclination angles were considered to investigate the pullout behavior from high-strength matrices. Furthermore, the pullout response from matrices with middle and low strength was examined, considering two embedment lengths. The results indicate that fibers with shorter embedment lengths exhibit lower pullout loads but higher energy absorption capacities. High matrix strength enhances adhesion and friction at the fiber-matrix interface, resulting in plumper pullout load versus slip curves. Owing to snubbing and matrix spalling effects, as the inclination angle increases, both the peak load and slip at the peak load of the inclined fibers exhibit an exponential increasing trend. Additionally, following the peak load, the pullout load of inclined fibers decreases more gradually than that of aligned fibers, and the energy absorption capacity of inclined fibers is significantly improved. Ultimately, general equations are derived for the calculation of pullout work and equivalent bond strength.

Investigation on selective laser-melted AlSi10Mg micro-struts: influence of processing parameters on dimensional accuracy, molten pool morphology and microhardness

PurposeThis study aims to address the limited understanding of the complex correlations among strut size, structural orientation and process parameters in selective laser melting (SLM)-fabricated lattice structures. By investigating the effects of crucial process parameters, strut diameter and angle on the microstructure and mechanical performance of AlSi10Mg struts, the research seeks to enhance the surface morphologies, microstructures and mechanical properties of AM lattice structures, enabling their application in various engineering fields, including medical science and space technologies.Design/methodology/approachThis comprehensive study investigates SLM-fabricated AlSi10Mg strut structures, examining the effects of process parameters, strut diameter and angle on densification behavior and microstructural characteristics. By analyzing microstructure, geometrical properties, melt pool morphology and mechanical properties using optical microscopy, scanning electron microscope, energy dispersive X-ray spectroscopy and microhardness tests, the research addresses existing gaps in knowledge on fine lattice strut elements and their impact on surface morphology and microstructure.FindingsThe study revealed that laser energy, power density and strut inclination angle significantly impact the microstructure, geometrical properties and mechanical performance of SLM-produced AlSi10Mg struts. Findings insight enable the optimization of SLM process parameters to produce lattice structures with enhanced surface morphologies, microstructures and mechanical properties, paving the way for applications in medical science and space technologies.Originality/valueThis study uniquely investigates the effects of processing parameters, strut diameter and inclination angle on SLM-fabricated AlSi10Mg struts, focusing on fine lattice strut elements with diameters as small as 200 µm. Unlike existing literature, it delves into the complex correlations among strut size, structural orientation and process parameters to understand their impact on microstructure, geometrical imperfections and mechanical properties. The study provides novel insights that contribute to the optimization of SLM process parameters, moving beyond the typically recommended guidelines from powder or machine suppliers.

Research on the Brazilian splitting characteristics and failure mechanism of jointed composite disks

The stress state of composite rock joints has a significant impact on the overall stability of the rock mass. Studying the composite mechanism disk specimens with different matrix strengths and inclination angles under Brazilian splitting state is of great significance for improving the safety of surrounding rock. This research conducted Brazilian tests on different types of jointed composite disk specimens at different inclination angles and explored the effects of inclination angle and material strength on the mechanical properties and deformation characteristics of specimens. Clarified the failure mechanism of joint specimen. The experimental results indicate that the disk specimens under different inclination angles exhibit three typical failure modes. As the inclination angle increases, failure mode changes from Disk matrix failure (DM failure) to Disk matrix and structural failure (DMS failure), and ultimately to Disk structural failure (DS failure). Failure load, input energy, and strain energy of the specimen continue to decrease as the inclination angle increases and the matrix strength decreases. The decrease in matrix material significantly weakens the strength of the specimen, but this effect continues to decrease with the increase of inclination angle. DIC results show that as the inclination angle increases, the position of cracks exists from the loading end to the joint surface. Through theoretical analysis, it is found that as the inclination angle increases, the stress state at the center of the specimens changes from compression-shear state to shear state, and finally to tension state, corresponding to three failure modes: DM failure, DMS failure, and DS failure, respectively.

Investigating the thermodynamic optimization of naturally convective flow in a corrugated enclosure: The influence of gap spacing and orientation of split baffles

The natural convection in cavities is frequently used in fluid mechanics and heat transfer engineering, such as heat exchangers, electronics, solar collectors, and growing crystals. However, the physics of natural convection flow and heat transfer in cavities with split baffles is least understood. The fundamental aim of this research is to investigate the impact of heated split baffles positioned at various locations on steady-state free convection within a sinusoidal corrugated star cavity. In this model configuration, the outer wavy enclosure is maintained at a constant temperature of Tc, while the inner split baffles are heated at a constant temperature of Th. The finite element method is employed to discretize and solve the governing equations describing the fluid flow and heat transfer within the enclosure. This numerical approach aimed to analyze the effects of baffle inclination angles, baffle spacing, Rayleigh number on the fluid dynamics and convective thermal transport characteristics. The variation in velocity and temperature profile is illustrated through the streamlines and isotherm contours. Moreover, the numerical result is displayed in term Nuavg of the heat transfer, which are analyzed for inside space of baffles and angles of the baffle (θ=00,450,900). The key finding demonstrates that increasing the Rayleigh numbers and the different positions (up, central, down) of inner vertical split baffles enhances the magnitude of the velocity by 88.1%, 85.9 and 89.6% respectively. Furthermore, for the inner rectangular split baffle angles of 0°,45°, and 90°, and within the Rayleigh number range of 104 to 106, the Nuavg exhibits significant variations, with maximum increases of 71.9% , 46.7% and a subsequent decrease of 45.9%.

Study on mechanical behavior of inclined cemented tailings composite backfill (CTCB) under uniaxial compression

The goaf volume in the vacancy method of hard rock mines is significantly larger than the filling capacity, forming layered and inclined planes during the large-scale filling process. This results in unclear mechanical impact mechanisms on the backfill. To investigate the effect of interface inclination angle on the mechanical behavior of backfill, a set of cemented tailings composite backfill (CTCB) samples with interface inclination angles of 15°, 30°, and 45° are prepared. Uniaxial compression tests and digital image correlation techniques are used to investigate the influence of various interface inclination angles on the strength, deformation behavior, and failure mode of the CTCB. The results show that: (1) The uniaxial compressive strength (UCS) of the CTCB weakens with increasing interface inclination angle but consistently shows exponential growth with curing age (CA) regardless of the interface inclination angle. (2) The interface inclination angle controls the behavior and classification characteristics of the stress-strain curve of CTCB samples, and the increase of interface inclination angle weakens the elastic modulus. (3) The interface inclination angle significantly influences the failure mode and classification characteristics of the samples compared to CA and tailing-to-cement ratio (TCR), with shear slip failure induced by the former and axial splitting failure induced by the latter. The research provides a theoretical basis for understanding the mechanical behavior and stability control of inclined CTCB in underground mining.

Influence of design parameters on natural convection heat transfer in additively manufactured body centered cubic lattice structures

The natural convection heat transfer mechanism of the body centered cubic (BCC) lattice structure needs to be clarified for its application in passive cooling thermal management. The BCC lattice heat sinks with various design parameters, such as strut diameter and unit cell length, were fabricated using the laser powder bed fusion process. Subsequently, the thermal performance was experimentally determined for variations in design parameters. The thermal performance tended to be maximized when the relative density of the lattice heat sink constituted approximately 10 %. The numerical analysis was performed to figure out the heat transfer mechanism and investigate the effects of inclination angles. According to numerical results, a lattice heat sink with a smaller strut diameter at the given unit cell length entrains more air than one with a larger strut diameter. However, decreasing strut diameter led to a negative impact on conduction and radiation heat transfer due to the reduction in solid region and surface area. Depending on the inclination angle, thermal performance of a lattice heat sink proportionally decreases. The main cause of performance degradation was the hindrance of plume motion by the base of the heat sink.

Experimental investigation on the effects of complex pressure gradients on the film cooling effectiveness of a serpentine nozzle

Serpentine nozzles more easily deform and damage due to high-temperature airflow because of their multi-bend channel configuration. Therefore, film cooling technologies should be applied to serpentine nozzles. Complex pressure gradients in serpentine nozzles lead to different film cooling characteristics from combustion chambers, turbine blades, and other exhaust systems. This study experimentally investigated the effects of complex pressure gradients and film hole inclination angles on a serpentine nozzle’s film cooling effectiveness (FCE) using pressure-sensitive paint (PSP). The flow mechanisms were obtained via numerical simulations. The experimental nozzle design needs to consider the needs of PSP observations and the normal flow of serpentine nozzles. However, the complex structure of serpentine nozzles makes those increasingly difficult. The studied pressure gradients include the pressure gradient mutation (PGM), strong adverse pressure gradient (SAPG), weak adverse pressure gradient (WAPG), and favorable pressure gradient (FPG). The results show that complex pressure gradients change the coolant coverage and adhesion and may induce a recirculation zone in the SAPG region. This affects the development of the vortex construction and leads to different FCE distributions. The FCE under the effects of the PGM is the largest, followed by the SAPG, WAPG, and FPG. A larger inclination angle weakens the coolant adhesion but may enhance its downstream and lateral flow treads. This is coupled with the effects of complex pressure gradients, where larger inclination angles bring better film cooling effects in some cases. After accounting for the four blowing ratios, the area-averaged FCEs under the effects of the SAPG, WAPG, and FPG are 28.9 %, 42.8 %, and 52.3 % lower than that under the PGM, respectively. The area-averaged FCEs under the conditions α = 45° and 60° are 6.6 % and 10 % lower than that under α = 30°.