Applied Mechanics and Materials Vols. 465-466

Abstract: In this paper, the effects of nozzles number on the internal flow in a counter flow Ranque-Hilsch vortex tube (RHVT) are studied. A 3D structured discretized model of a counter flow multi nozzle RHVT is developed to study the dynamic behaviour of the highly swirling, compressible turbulent flow. Simulations of the turbulent flow are performed using standard k-ε model with 2, 4, 6 and 8 number of nozzles at the computational inlet. Total temperature profiles and total energy separations are studied as a function of nozzle number and total nozzle cross section area. It is observed that cooling effect increases as the nozzle number increases irrespective of total nozzle cross section area.

Abstract: The findings of computational fluid dynamics simulation results performed on an industrial roller-kiln are presented here. The modification was emphasized on the temperature distribution during the drying process of ceramic-tiles. A computational fluid-dynamics solver was used in the modeling and simulation of the temperature distribution. Boundary conditions for the burners were setup with different temperature outputs for the burners, indicated as initial settings and modified burner configuration settings. The simulation results were shown in contour-plots, demonstrating consistent heat circulation throughout the drying chamber near the burner regions. The comparison of initial and secondary simulation results also demonstrated consistent temperature distribution near the ceramic-tiles region within the drying chamber. This consistency in heat transfer has proven that similar temperature can be achieved with less gas, despite the change in burner-temperature configuration.

Abstract: In this experiment, the cold mass fraction, cold temperature difference and isentropic efficiency of Ranque-Hilsch Vortex Tube were investigated and measured. Three different inlet pressures (absolute) (296633 Pa, 394699.5 Pa and 492766 Pa) and 2 type of orifice diameter (4 mm and 5 mm) were used. 5 mm orifice gives higher value of cold mass fraction (μ_c = 0.7067) compare to 4 mm orifice (μ_c = 0.3264). It is also no significant effect in cold mass fraction by changing three difference inlet pressures. 4 mm orifice has higher cold temperature difference (ΔT_c = 18°C) compare to 5 mm orifice (ΔT_c = 8°C) at highest inlet pressure (492766 Pa) that were used. 4 mm orifice has higher isentropic efficiency (η_isen=0.17545) compare to 5 mm orifice (η_isen=0.0834). For both orifices, the highest isentropic efficiency was obtained when the lowest inlet pressure (296633 Pa) were applied.

Abstract: The most important problem that faces spraying application process in the field is spray losses as result to spray drift to non target areas by action of air flow. Spray drift from conventional TeeJet even flat nozzle TPE and Drift Guard Even flat nozzle DGE (pre orifice nozzle) for banding application was investigated and compared under wind tunnel conditions. This paper examined effect nozzle heights 50 and 60 cm on spray drift. To determine the effect of wind speed on spray drift, wind tunnel was used to product three cross wind speeds 1, 2 and 3m/s. According to the results from this study, nozzle type affected significantly the spray drift. Increasing wind speeds had a high significant effect on increasing the spray drift. Nozzle height affected significantly the spray drift, the closer the nozzle is to the ground, the more the likelihood of spray drift is minimized. This study supports the use of nozzle type DGE as a means for minimizing spray drift.

Abstract: Turning diffuser is an engineering device that is widely used in the industry to reduce the flow velocity as well as change the direction of the flow. Having a curvature shape causes its performance to decrease in terms of pressure recovery (C_p) and flow uniformity (σ_u). Therefore, this study presents the work done in designing baffles to be installed in the turning diffuser with ratio of AR=2.16 to improve the flow uniformity and pressure recovery. It also aims to investigate the mechanism of flow structure and pressure recovery in turning diffusers by means of turning baffles. The results with varying inflow Reynolds number (Re_in) between 5.786E+04 1.775E+05 have been experimentally tested and compared with previous study. Particle image velocimetry (PIV) was used to determine the flow uniformity. On the other hand, a digital manometer provided the average static pressure of the inlet and outlet of turning diffuser. The best produced pressure recovery of C_p=0.526 were recorded when the system were operated at the highest Reynolds number tested Re_in=1.775E+05. This result shows an improvement up to 54.625% deviation from previous study with C_p=0.239. The flow uniformity also shows an improvement of 47.127% deviation from previous study at the same Re_in with σ_u=3.235 as compared to previous study σ_u=6.12.

Abstract: This paper discusses the two phase (gas/Particles) flow effect of interior ballistic performance in a 76 mm naval medium caliber gun with guided projectile, using granular seven-perforated propellant. The theoretical and numerical simulation of the two phase flow in the interior ballistic cycle is carried out by using MacCromack technique depending on the governing equations of the two phase flow. This simulation is considered to be helpful for the prediction of the interior ballistic parameters which are required for endurance of guided projectile. A good agreement between the simulation results compared to the experimental results is fulfilled. Keywords: Guided projectile, two phase flow modeling, Interior ballistic, Computational fluid dynamics.

Abstract: Numerical investigation of heat transfer enhancement in two-dimensional microchannel heat sink (MCHS) using Al₂O₃-water, CuO-water and TiO₂-water was conducted. The effect of different type of nanoparticles at particle volume concentration of 1%, 2% and 5% on the thermal performance in the MCHS was examined. The thermal performance is increased when nanofluids with high thermal conductivity and low dynamic viscosity was used. As the particle volume concentration increases, the heat transfer performance also improved. The result shows that the heat transfer performance of all the nanofluids used in this study was better than that of pure water. Overall, nanofluids with Al₂O₃-water at 5% particle volume concentration show the best cooling performance.

Abstract: Unsteady computations of laminar flow have been performed for two-dimensional configurations of micro-channel equipped with two synthetic jets. The effect of phasing has been investigated at in-phase and 180̊ out-of-phase of the synthetic jet actuators at a fixed operating frequency and oscillating amplitudes. It was shown that the 180̊ out-of-phase configuration of the synthetic jets promotes better and more continuous flow mixing within the channel during the oscillation. This was due to the discrete pattern of vortex forming which disrupts the main channel flow. The 180̊ out-of-phase jet configuration exhibits higher cooling performance compared to the in-phase jet configuration in terms of the reduction in the maximum temperature in the silicon wafer.

Abstract: Present study involves experimental and numerical work to investigate the effect of integral wake splitter towards the overall performance of cross-flow, circular tube, heat exchanger system. The experimental work was conducted to obtain local distribution of pressure coefficient around plain tube bank of staggered arrangement which was subjected to a cross-flow of air with Reynolds number of 15950. The numerical work consisted of 2-dimensional unsteady numerical simulation which was validated against the experimental data. The validated numerical approach was utilized to simulate cross-flow around similar tube bank but with integral wake splitter of length-to-diameter ratio of 0.5, 1, 1.5 and 2, at Reynolds number between 5000 to 50000. It is concluded that integral wake splitter is able to reduce pressure loss, which in turn reduces power requirement of a blower, which is intended in effort to increase the system efficiency. Splitter which acts as fin may improve the overall performance of the system by enhancing total heat removal via extended surface provided that certain value of fin efficiency is achieved.

Abstract: Energy is one of the most important sources in the world especially for developing countries. The subject study is conducted to predict the behaviour of particle due to errosion from the river through the achimedes screw runner and predict the impact of particle toward blade surface. For this reason, computational fluid dynamics (CFD) methods are used. The three-dimensional flow of fluid is numerically analyzed using the Navier-Stokes equation with standard k-ε turbulence model. The reinverse design of archimedes screw blade was refered with the previous researcher. Flow prediction with numerical results such as velocity streamlines, flow pattern and pressure contour for flow of water entering the blade are discussed. This study shows that the prediction of particle impact occurs mostly on the entering surface blade and along the leading edge of the screw runner. Any modification on the design of the screw runner blade can be analyze for further study.