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%.
Chemical Engineering
Z. Aouissi; F. Chabane; M. S. Teguia; N. Belghar; N. Moummi; A. Brima
Abstract
This numerical and experimental work aims to improve the heat transfer inside a solar thermal collector. By incorporating rectangular baffles in the middle of the distributed air passing channel at different angles of inclination (ß= 90°, ß= 180°, ß= 180° and ß= 90°). ...
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This numerical and experimental work aims to improve the heat transfer inside a solar thermal collector. By incorporating rectangular baffles in the middle of the distributed air passing channel at different angles of inclination (ß= 90°, ß= 180°, ß= 180° and ß= 90°). That is called the model H. These experiments were carried out in the Biskra region of Algeria in good natural conditions with an average solar radiation approximately constant I= 869 W/m2 varying from 11:30 to 14:00. After the completion of the experimental investigation, a computational fluid dynamics (CFD) model was created that matches this experimental model with the same experimental boundary conditions. In the numerical study, ANSYS Fluent 18.1 was used to conduct simulations and compare the results of the thermal and hydraulic performance of the collector. It was concluded that the effectiveness of the CFD model, meaning that the theoretical and numerical data were very close to each other for all mass flow rates. As the mass flow increased the heat transfer process increased, while the absorber plate temperature inside the collector for experimental and numerical studies decreased. Addition of baffles increased heat transfer, due to the creation of turbulent flow that leads to crack the dead thermal layers near the absorber plate, which leads to an increase in heat transfer from the absorber plate to the air.
