Chemical Engineering
N. Hedayati; A. Ramiar
Abstract
The challenge of particle deposition in microchannels has consistently posed issues in nanofluids, adversely impacting the heat transfer rate. This study investigates the novel approach of employing a magnetic field to prevent deposition and enhance the heat transfer of nanoparticles in microchannels, ...
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The challenge of particle deposition in microchannels has consistently posed issues in nanofluids, adversely impacting the heat transfer rate. This study investigates the novel approach of employing a magnetic field to prevent deposition and enhance the heat transfer of nanoparticles in microchannels, utilizing Euler-Lagrange method. The analysis involves the coupled solution of momentum and energy equations, incorporating forces such as Brownian motion, thermophoresis, drag, and volumetric force. The findings within the explored parameters indicate that temperature variations affecting particles beyond the thermal boundary layer have a comparatively minor impact compared to those within the boundary layer. This presents an opportunity for optimizing nanoparticle consumption. Additionally, the study reveals that a non-developed flow at the inlet results in lower particle deposition compared to a developed inlet. The results show that an increase in the Reynolds number from 50 to 300 leads to a 1.75% increase in the distance of particles from the wall. The study also delves into the positioning of the current-carrying wire, demonstrating that placing the wire at the microchannel entrance significantly reduces particle deposition. Furthermore, the results indicate that with an increase in electrical current up to 4 amperes, the efficiency of non-deposition reaches 100%.
Energy
P. Hedayati; A. Ramiar; N. Hedayati
Abstract
Wind energy is a prominent renewable energy source, and Vertical Axis Wind Turbines (VAWTs) offer distinct advantages, including adaptability to changing wind directions and reduced noise levels. This paper conducts a numerical investigation into the impact of flat and curved stator blades on VAWTs, ...
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Wind energy is a prominent renewable energy source, and Vertical Axis Wind Turbines (VAWTs) offer distinct advantages, including adaptability to changing wind directions and reduced noise levels. This paper conducts a numerical investigation into the impact of flat and curved stator blades on VAWTs, specifically the Savonius turbine, under 2D, viscous, turbulent, and steady flow conditions. Four stator blade configurations were examined, including no stator blades, smooth stator blades, twisted stator blades (Case A), and both blades being concave (Case B). The study reveals that curved stator blades enhance VAWT performance, with Case B exhibiting the most efficient performance. The results show pressure distribution on the turbine blades is non-uniform, with high and low-pressure zones, predominantly on the windward side. The presence of stator blades enhances pressure on all turbine blades, with Case B exhibiting the most optimal pressure distribution. Detailed observation of streamline and velocity distribution reveals improved flow lines for Case B, leading to more effective turbine blade performance. Case B consistently produces the highest turbine torque, with a maximum value of approximately 2.1 N·m achieved at Re = 15750. The torque demonstrates a positive correlation with increasing Reynolds numbers. The study further introduces a non-dimensional torque ratio analysis, where Case B attains 7.59 times higher torque than the reference case at Reynolds number 15750. The sensitivity of torque increase with respect to Reynolds number change highlights that Case B (with a slope of torque increase at around 4.5e-04) is the most responsive within the studied Reynolds number range.
Energy
N. Hedayati Goodarzi; M. Rahimi-Esbo
Abstract
Steam reformers are typically utilized in hydrogen production industry, demanding pressure vessels within methanol reformer systems operating at temperatures between 250-350°C to ensure cost-effectiveness. This characteristic makes them a superior choice for fuel cell systems. However, challenges ...
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Steam reformers are typically utilized in hydrogen production industry, demanding pressure vessels within methanol reformer systems operating at temperatures between 250-350°C to ensure cost-effectiveness. This characteristic makes them a superior choice for fuel cell systems. However, challenges arise in enhancing hydrogen gas production efficiency while minimizing carbon monoxide emissions. Computational Fluid Dynamics (CFD) has proven effective in addressing these challenges by simulating fluid behavior. This study delves into product production, reactant consumption using CFD, and investigates changes in physical parameters of methanol reformers to optimize their performance. The research involves 140 numerical simulations that examine the relationship between feeds (steam-to-carbon) and various temperatures, aiming to understand the concurrent effect of physical parameters. The results demonstrate that increasing temperature has a more significant impact on hydrogen production compared to increasing the feed ratio. This effect is particularly notable at lower fuel ratios. For example, at a feed ratio of 1, a temperature increase of 11.4°C leads to a substantial 5.4% rise in hydrogen production. However, at a higher feed ratio (1.98), the increase in hydrogen production is only 1.9% with the same temperature increase.
