AUT Journal of Mechanical Engineering
https://ajme.aut.ac.ir/
AUT Journal of Mechanical Engineeringendaily1Sat, 01 Jun 2024 00:00:00 +0330Sat, 01 Jun 2024 00:00:00 +0330Simultaneous Effects of a Vortex Generator and Magnetic Field on Ferrofluid Convective Heat Transfer in a 3D Channel: First and Second Law Analyses
https://ajme.aut.ac.ir/article_5498.html
This paper presents a comprehensive approach to enhance heat transfer rates in a 3D channel using Ferrofluids. The study investigates the individual and combined impacts of rectangular winglet vortex generators and magnetic fields on flow characteristics, heat transfer enhancement, and entropy generation. Numerical solutions are derived for the governing partial differential equations using the finite volume technique and the SIMPLE algorithm. The investigation assesses the influence of key parameters, including the type of rectangular winglet vortex generator (simple, concave, and convex), Reynolds number, and magnetic field strength. Optimal operational conditions are identified based on thermodynamics' first and second laws. This study has been conducted in three steps. Firstly, the effect of the vortex generator at different Reynolds numbers is investigated. Subsequently, the impact of applying a magnetic field (via a current-carrying wire) at different intensities is studied. Finally, the application of vortex generators and magnetic fields has been investigated simultaneously. The results showed that using the concave vortex generator in the absence of a magnetic field increased the heat transfer by 50% and pressure drop by 60%. Applying a magnetic field in the channel without vortex generators has increased heat transfer and pressure drop by 70% and 118%, respectively. The simultaneous application of magnetic field and vortex generator has also increased the heat transfer and pressure drop by 200% and 269%, respectively.Experimental study of thermal gradient effect on reverse osmosis process
https://ajme.aut.ac.ir/article_5488.html
In the present work, an experimental study of the thermal gradient effect on the reverse osmosis process is performed to evaluate pure water penetration and water production under the effect of the temperature gradients and the salt concentration. The experimental study uses a novel experimental setup designed and built for the present work. The DOW Filmtec RO membrane, SW30HR, was used in the experimental setup. The results showed that, this process is dependent on salt concentration and temperature gradient between permeate-water and saline-water side. It is observed that in 10.8oC temperature difference between the permeate-water and the saline-water part for 1 gr/lit salt concentration at saline-water part, the Process time is 20 min, water flux is 0.142kg/(m^2 s) and salt concentration in saline-water part varies from 1.04 gr/lit to 1.22 gr/lit. In addition, for 1.5oC temperature difference between permeate-water part and the saline-water part for 1 gr/lit salt concentration at saline-water part, the Process time is 35 min, water flux is 0.043kg/(m^2 s) and salt concentration in saline-water part varies from 1.004 gr/lit to 1.059gr/lit. It can be concluded, while temperature gradient increases, the Process time decreases, and pure water penetration from saline-water to permeate-water part also increases. As a result, the salt concentration and electrical conductivity can increase in the saline-water part.Optimum design of a viscoelastic vibration absorber for counter-rotating systems
https://ajme.aut.ac.ir/article_5489.html
The small distance between two rotating shafts can disturb them, cause interference in their performance and affect the system's efficiency. Application of the counter-rotating double shafts has some specific benefits. For example, these shafts can be used under the water to neutralize the driving torque effect, prevent from the submarine's self- propulsion, and increase the submarine's power to move forward and maneuver. The aim of this study is designing an optimum viscoelastic vibration absorber for Counter-Rotating Double Shaft to deal with the vibration. In order to overcome vibrations, Viscoelastic cylinders are modeled as distributed spring and damper which are considered between the two shafts and their vibration equations are obtained. Optimal position and distributed stiffness and damping coefficients are determined using particle swarm optimization algorithm. The objective function to be minimized is defined as relative distance between shafts which is controlled by Equivalent stiffness and damping coefficients of considered viscoelastic vibration absorber. The present results show that applied viscoelastic polymer with the nearest features to the optimum values can drastically decrease the relative distance between shafts and absorb the vibration of rotating shafts.Numerical Simulation of the Bubble Dynamics Inside an Enclosure Containing Blood under the Influence of Pressure Oscillations
https://ajme.aut.ac.ir/article_5493.html
This study investigates the evolution of bubble shape within a square area filled with blood. The accuracy of the numerical solution is validated using Laplace's problem and the free rising of the bubble. The analysis is conducted in two dimensions and in a transient manner. The effects of ultrasound waves are applied as a function of pressure on the boundaries of the solution domain. Results show that by applying a linearly increasing of pressure on the computational domain boundaries causes a reduction in bubble radius. Furthermore, it is observed that by assuming the air inside the bubble behaves as an ideal gas, leads to more pronounced changes in bubble radius compared to constant density assumptions. Oscillatory pressure distributions on the external boundaries result in corresponding oscillations in bubble radius. These fluctuations in bubble size could be utilized to exert tension on the walls of blood clots, ultimately aiding in their dissolution. The most intensive bubble size fluctuations occur in the frequency of 1 (MHz). Additionally, the disproportionate changes in bubble radius with pressure variations are attributed to the hysteresis phenomenonExperimental investigation of fin heat transfer characteristics in different condition
https://ajme.aut.ac.ir/article_5491.html
The application of heat sinks as an extended surface has a significant role in the cooling of many industrial equipment. In this study, the effect of the parameters of heat transfer of the fins such as the effect of practical geometry, wall heat flux, coolant velocity and its impact angle with the fin is experimentally investigated. The geometry includes rectangular and triangular shapes, the applied heat flux range is about 4.6-18.5 (kw/m2), the coolant velocity is between 1-2 (m/s), and the angle between the fin position and cooling flow direction were chosen in 0&ordm;, 45&deg; and 90&ordm;. Also, the air as a primary cooling flow is considered, while aluminum as a practical and high conductivity metal was chosen for fin structure material. Finally, it is found that the convective heat transfer rate on the triangular fin is higher than the rectangular type, while the dissipation heat rate from the wall by using the rectangular fin is more than the other. In addition, the pressure drop was estimated by comparing the cooling flow velocity related to each fin in different positions. Also, the comparison between the efficiency of rectangular and triangular fins shows that the efficiency of rectangular fins is more than triangular and also it is found that the effect of impact angle on the efficiency of rectangular and triangular fins can be negligible.