Impact Of Geometric Parameters Research Articles

Optimizing Heat Transfer in Vertical Helical Coils: A Comprehensive CFD Investigation into the Impact of Geometric Parameters on Inner Heat Transfer Coefficient

Optimizing Heat Transfer in Vertical Helical Coils: A Comprehensive CFD Investigation into the Impact of Geometric Parameters on Inner Heat Transfer Coefficient

A broadband hybrid energy harvester with displacement amplification decoupling structure for ultra-low vibration energy harvesting

Abnormal vibration of electrical equipment requires a large number of distributed sensors to monitor. However, there are issues that require maintenance and power supply. This work proposes a working mode for harvesting the low-grade vibration energy of electrical equipment, which can replace vibration sensors and achieve self-powered monitoring of equipment vibration. Additionally, we present a novel energy harvesting module that solves the issue of converting random vibration into linear vibration. The introduction of laminated hinges achieves large displacement output under small amplitude vibration and energy harvesting from random low amplitude vibration within a bandwidth of 2–23 Hz. The impact of geometric parameters on the proposed system is evaluated through parameter analysis. Experimental findings reveal that the device can achieve a maximum power output of 17.84 mW at an ultra-low 0.05 g acceleration., resulting in a peak power density of approximately 44.87 W/m3. Compared to traditional methods, peak power has increased by 266.2 %. Wireless vibration online monitoring systems for visualizing vibration status are created by combining the equipment with repeaters and phones. This research introduces a unique strategy for remote online vibration monitoring that may be used in distributed sensor systems to identify malfunctioning machinery.

Pool Boiling of Ethanol on Copper Surfaces with Rectangular Microchannels

In this paper, pool boiling of ethanol at atmospheric pressure was analyzed. The enhanced surfaces were made of copper, on which grooves with a depth ranging from 0.2 to 0.5 mm were milled in parallel. The widths of the microchannels and the distances between them were 0.2 mm, 0.3 mm and 0.4 mm, respectively. The highest heat transfer coefficient, 90.3 kW/m2K, was obtained for the surface with a microchannel depth of 0.5 mm and a width of 0.2 mm. The maximum heat flux was 1035 kW/m2. For the analyzed surfaces, the maximum heat flux increase of two and a half times was obtained, while the heat transfer coefficient increased three-fold in relation to the smooth surface. In the given range of heat flux 21.2–1035 kW/m2, the impact of geometric parameters on the heat transfer process was presented. The diameters of the departing bubbles were determined experimentally with the use of a high-speed camera. A simplified model was proposed to determine the diameter of the departure bubble for the studied surfaces.

Cyclic behavior of channel-encased braces incorporating round HSS

Bracings made with cold-formed round hollow structural shapes (HSS) are commonly utilized in ductile concentrically braced frames (CBFs) in seismic regions for their efficiency in terms of high load-bearing capacity and ease of construction. Bracings are expected to sustain a ductility demand that ranges between 10 and 20 without fracture when ductile CBFs subject to severe earthquake ground motions. However, the experimental findings accentuate that ductile braces, even those with round HSS that possess impractically small diameter-to-wall thickness ratios (D/t), are prone to premature fracture. Thus, developing a simple and cost-effective performance-enhancing system for existing conventional CBFs incorporating round HSS could be imperative to mitigate the potential seismic risk. For this purpose, an existing round HSS is encased in two channels to form a buckling-controlling mechanism that is expected to improve the seismic hysteretic behavior, consequently, the energy dissipation capacity of ductile braces. Experimental and parametric numerical studies have been conducted to comprehend the level of improvement in the cyclic behavior and the impact of geometric parameters (i.e., slenderness and D/t ratios). The overarching results indicate that channel-encased bracing improves the seismic hysteretic behavior, yielding a stable and symmetric cyclic response. In addition, the results suggest that the optimal design parameters, including gap amplitude and encasing thickness, play a critical role in achieving desired ductility level.

Terahertz absorber with switchable functionality from ultra-broadband to broadband

In this paper, we present a terahertz absorber with switchable absorption modes by utilizing patterned graphene‑vanadium dioxide. Through thermal tuning of vanadium dioxide and electrical control of graphene, our device demonstrates two distinct absorption modes that can be switched between. By maintaining the Fermi energy of graphene at 1 eV, the device achieved an ultra-broadband absorption with a bandwidth of 4.62 THz, spanning from 3.58 to 8.20 THz, when the conductivity of vanadium dioxide reached 200,000 S/m. Once the conductivity dropped to 200 S/m, we observed a narrower bandwidth of 0.95 THz (ranging from 6.58 to 7.53 THz) for the broadband absorption. At this stage, manipulating the Fermi energy of graphene allows for control over the amplitude and frequency shift of the broadband mode. Additionally, the device benefits from a remarkable degree of symmetry, which guarantees its insensitivity to changes in polarization angle. The impact of geometric parameters on the robustness of absorption characteristics is also discussed. The device may have potential applications in broadband mirror and electromagnetic shielding and so on.

Impact of geometric parameters and inlet boundary conditions on the behavior of a cyclone separator

Impact of geometric parameters and inlet boundary conditions on the behavior of a cyclone separator

Numerical Analysis of the Impact of Geometric Parameters of the Outcuts in the Wing Torsion Box Wall on the Mechanical Properties of the Structure

Numerical Analysis of the Impact of Geometric Parameters of the Outcuts in the Wing Torsion Box Wall on the Mechanical Properties of the Structure

Numerical study of the effects of geometric parameters and nanofluid properties on heat transfer and pressure drop in helical tubes

In this research the geometric parameters and nanofluid properties effects on heat transfer and pressure drop in helical tube, by using alumina-water nanofluid as cooling fluid, are numerically investigated. Friction factor and heat transfer coefficient are calculated by considering the effects of nanofluid properties, including nanoparticle diameter, nanofluid temperature, Reynolds number, and volume fraction, on the one hand, and the impact of geometric parameters, including tube diameter, coils diameter and coils pitch, on the other hand. Numerical analysis is performed in the Ansys Fluent 19.2 software using the SST k-ω turbulence model. By increasing the nanofluid volume fraction the heat transfer coefficient and pressure drop in helical coils increase, the same as the nanoparticle diameter reduction. The reduction of nanoparticle diameter causes an enhancement of heat transfer and friction factor, the best results happen in dp = 5 nm and φ = 4%, where the it was ~ 40.64% more efficient than base fluid. This amounts for φ = 3%, φ = 2% and φ = 1% are 31.80%, 18.02% and 8.83%, respectively. Finally, the performance evaluation criteria (PEC) is compared for different cases, the maximum value was happen on φ = 4% and dp = 5 nm, which it is 1.86 times higher than the base fluid. The results indicate that the thermal efficiency of the heat exchanger improve largely by using helical coils and nanofluids, rather than the base fluid, and direct tubes. In addition, increasing coil pitch and curvature ratio enhance heat transfer and reduce friction factor.

Time domain spectral element-based wave finite element method for periodic structures

In this work, a time domain spectral element-based wave finite element method is proposed to analyze periodic structures. Time domain spectral element-based formulation reduces the total degrees of freedom and also renders a diagonal mass matrix resulting in substantial reduction in computation time for the wave finite element method. The formulation is then considered to obtain the stop band characteristics for a periodic bar and a Timoshenko beam considering geometric as well as material periodicity. The impact of geometric parameters on the stop bands of 1-D structures is then investigated in detail. It is shown that the stop bands can be obtained in the frequency range of interest, and its width can be varied by tuning those geometric parameters. Also, the effect of material uncertainty is studied in detail on the stop band characteristics of periodic 1-D structures, and the same formulation is utilized for Monte Carlo simulations. Results show that randomness in density influences more the bandwidth of the stop bands than that of elastic parameters.

Mathematical Modeling and Characteristic Analysis of the Vertical Stiffness for Railway Vehicle Air Spring System

Establishing a correct and reliable vertical stiffness model has an important significance on reproducing the characteristics of an air spring system. In this paper, a dynamic vertical stiffness model is developed based on thermodynamics and fluid dynamics, and geometric parameters are identified by an approximate analytical method. Meanwhile, experimental tests are performed to verify the accuracy and reliability of the proposed model. Furthermore, the impact of geometric parameters on the vertical stiffness characteristics is discussed through a sensitivity analysis. The conclusions show that the dynamic vertical stiffness model can well characterize the dynamic characteristics of the air spring system, which provides a theoretical basis for the optimal design of air spring parameters and the study of mechanical properties.

Research on nonlinear modeling and dynamic characteristics of lateral stiffness of vehicle air spring system

This paper established a lateral stiffness coupling model to investigate the lateral characteristics of air spring system under crosswind conditions. The nonlinear super-elastic characteristics, coupling characteristics of the air spring, lateral stiffness characteristics of emergency spring, and damping force are studied. The accuracy of the lateral stiffness model is validated by comparing with experimental data. In addition, the impact of geometric parameters on the lateral stiffness characteristics is discussed by a sensitivity analysis method, as well as the effect of the lateral stiffness model on vehicle mechanical performance is analyzed. The conclusions show that the lateral stiffness model can well predict the lateral characteristics of the air spring system, and provide theoretical guidance for the parameter design of rail vehicles and vehicle ride comfort improvement.

Influence of the pressure relief door area and aspect ratio on discharge and force characteristics

Purpose The purpose of this paper is to analyze the effects of the PRD geometric parameters, including the area and aspect ratio, on the discharge and force characteristics of pressure relief process under various plenum compartment pressures and Mach numbers. Design/methodology/approach Under various plenum compartment pressures and Mach numbers, the effect of the area and aspect ratio on the discharge and force characteristics of the PRD are numerically investigated via a three-dimensional steady Reynolds-averaged Navier–Stokes equations solver based on structured grid technology. Findings When the aspect ratio remains constant, the discharge coefficient CD, thrust coefficient CT and moment coefficient CM are not affected by the PRD. When the area is constant, the aspect ratio dramatically impacts the discharge and force characteristics because the aspect ratio increases, the discharge coefficient CD of the PRD decreases, and the thrust coefficient CT and the moment coefficient CM both increase. When the aspect ratio is 2, the discharge coefficient CD decreases by 14.7 per cent, the thrust coefficient CT increases by 10-15 per cent, and the moment coefficient CM increases by 10-23 per cent compared with when the aspect ratio is 1. Practical implications This study provides detailed data and conclusions for nacelle PRD researchers and actual engineering applications. Originality/value On the basis of considering the influence of operating conditions on the discharge and force characteristics of the nacelle PRD, the impact of geometric parameters, including the area and aspect ratio on the discharge and force characteristics is comprehensively considered.

CFD and experimental investigation into a non‐intrusive method for measuring cooling air mass flow rate through a synchronous generator

This study presents a detailed methodology for non-intrusive measurement of cooling air mass flow rate that enables an overall machine evaluation. This approach enables the simultaneous measurement of air mass flow with shaft torque at differing operating points while minimising the change in air flow introduced by the measurement system. The impact of geometric parameters in the designed system is investigated using a detailed 180° computational fluid dynamics (CFD) model. Special attention was paid to minimising their influence on pressure drop, the mass flow rate through the machine, and measurement uncertainty. Based on the results of this investigation, the system was designed and manufactured, and the experimentally measured data was used to validate the CFD predictions. For the as optimal identified configuration, the flow rate is predicted to decrease by 2.2% relative to unrestricted operation. The achieved measurement uncertainty is ± 2.6% at synchronous speed.

Studies on effusion cooling: Impact of geometric parameters on cooling effectiveness and coolant consumption

This study is focused on the impact of certain important geometric parameters on cooling effectiveness and coolant consumption for effusion cooling of aircraft combustor liner. The three dimensional turbulent flow field in a domain representing the combustor with several rows of effusion coolant injection is considered for the analysis. The geometric parameters considered are: angle of injection of the coolant, axial and transverse pitch of the injection holes, hole spacing and hole diameter. Also, based on the analysis of the temperature field within the chamber, a novel concept of ‘variable hole diameter’ has been introduced to reduce coolant consumption. A symmetric 3D computational model including the combustion chamber, coolant chamber and the effusion plate was used for the study. Conjugate heat transfer was modeled between the effusion-cooled wall and the two chambers. A detailed mass flow rate analysis has been performed for the various cases in order to study the impact of parameters on coolant consumption. The proposed approach of using an effusion plate with variable hole diameters is found to be effective in reducing the net coolant consumption significantly while maintaining a given level of cooling effectiveness.

Influence predictions of geometric parameters on face gear strength

Strength research is always one of the study focuses of face gear drives. However, a strength calculation solution, in which bending stresses, contact stresses, and bulk temperatures are included, combined with gear design standards for face gear drives, is still not constructed due to complex face gear teeth. Thus, in this study, an equivalent face gear tooth is proposed by assessment of geometric characteristics of face gear teeth and tooth contact analysis, and a strength calculation solution of face gear drives, which is based on ISO 6336 standard associated with the proposed equivalent face gear teeth, is constructed. The fidelity of the proposed strength calculation solution of face gear drives is verified by comparing its results with the benchmark of results by finite element methods. Furthermore, the impact of geometric parameters on the strength of face gear drives is investigated, and some design suggestions are extracted. These contributions would benefit the improvement of engineering applications of face gear drives.

Impact of Geometric Parameters, Charge, and Lipophilicity on Bioactivity of Armed Quinoxaline, Benzothiaole, and Benzothiazine: Pom Analyses of Antibacterial and Antifungal Activity

A series of four different armed heterocyclic candidates; 1-(2-methyl-2,3-dihydro-1,3-benzothiazol-2-yl)acetone (2), 1-(3-methyl-4H-1,4-benzothiazin-2-yl)ethanone (3), 2-[(2-aminophenyl)dithio]aniline (4), and 3-hydroxy-3-methyl-4-(3-methyl-2-quinoxalinyl)-2-butanone (5) have been prepared and their microbial activities were evaluated. A correlation of the structure and activities relationships of these compounds with respect to molecular modeling, Lipinski Rule of Five, drug likeness, toxicity profiles, and other physico-chemical properties of drugs are described and verified experimentally.

Design, fabrication and characterization of a perfect absorber using simple cut-wire metamaterials

Using an irreducible design we experimentally and numerically study a perfect metamaterial absorber, providing excellent absorption at microwave frequencies. The impact of geometric parameters on the absorption is also investigated. The experimental and the simulated results are in good agreement. Finally, we propose a polarization-insensitive absorber for the improvement.