Semarak Journal of Thermal-Fluid Engineering

Analysis of Airflow Characteristics of Different Models of Unmanned Aerial Vehicles

Muhammad Zharif Mohd Noor — 2024-09-30

Unmanned aerial vehicles or drones have become popular in civil as well as military operations in recent years. Such developments call for new UAV designs that are able to perform a variety of missions. A UAV is an aircraft that operates independently or is operated remotely without occupant on board. This feature makes the system safer and cheaper than manned systems as indicated in the following sub-sections. In this paper, the authors pay attention to the assessment of aerodynamic characteristics of two different UAV models through CFD analysis. In the simulations, factors like the drag coefficient, lift, and velocity vectors were examined to enhance the UAV characteristics. In the flow pattern of Model 1, the airflow was strongly bounded to the UAV surface and hence high velocity zones and strong wing lift were observed. However, Model 2 had flow separation at the wing trailing edge; this increases drag and can lead to aerodynamic problems. The results of the simulation show that Model 1 had a higher lift and drag force of 15.162505 N and 16.392923 N respectively while Model 2 had almost no effect on the lift and drag forces. These differences can be explained by differences in the shape of the wings and the approach used in their design. Further, this research analyzed the effects of the wing loading on the UAV performance in the stall speed, climb rate, takeoff distance, and efficiency. These results indicate that CFD has a significant function in identifying the aerodynamics that offer understanding of UAVs with better performance. This research benefits the field of UAV and enhances the performance in both military and civil fields.

Temperature Distribution in a Cooled Room

Siti Khadijah Azhar — 2024-09-30

A 3-dimensional numerical study was conducted to compare the computational and experimental results of airflow characteristics and temperature fields in the activity areas of Kolej Kediaman Tun Dr. Ismail (KKTDI) and Kolej Kediaman Tun Fatimah (KKTF), focusing solely on their indoor environmental conditions. Two methods were employed: experimental measurements and computational simulation using the Computational Fluid Dynamics (CFD) approaches. The validation process involved comparing the proposed simulation with previous experimental results, focusing on velocity and temperature results. The average relative error of the velocity was 12.59%, which was considered acceptable because it was less than 20%. This error was observed only at the KKTF, as no velocity was recorded at the KKTDI (0 m/s at all lines). The temperature simulation consistently showed 18°C across all lines. The experimental results for the KKTF ranged from 16.4°C to 17.8°C, whereas the KKTDI temperatures ranged from 27.8°C to 28.9°C. Comparing the simulation and experimental results, the KKTF results were similar, with differences ranging from 0.2°C to 1.6°C across the curves. However, the KKTDI exhibited significant differences, ranging from 9.2°C to 10.9°C across lines. This study successfully demonstrated the accuracy of the airflow characteristics and temperature field data obtained in the two active halls. The results provide valuable insights into the indoor environmental conditions of the KKTDI and KKTF, highlighting the importance of proper ventilation system design and equipment placement in managing heat accumulation. The results contribute to a better understanding of indoor environmental dynamics and can inform the future design and optimisation of similar spaces.

Computational Analysis of Shell Components in a Single Shell-and-Tube Heat Exchanger

Chee Wai Leon — 2024-09-30

This study investigates the optimisation parameters of a single-segment baffle, one-pass shell-and-tube counterflow heat exchanger, which is commonly used in industry. The objective was to minimise the pressure drop while optimising the heat transfer efficiency by using suitable tube arrangements, baffle cuts, and baffle inclination angles. The overall heat transfer coefficient and total heat transfer rate were calculated using the logarithmic mean temperature difference (LMTD) method. ANSYS FLUENT v19.2 and SOLIDWORKS 2018 were used to simulate incompressible liquid water model under steady-state conditions. The tested parameters included tube arrangements at 20°, 45°, 60°, and 90°; baffle cuts at 25% and 36%; and baffle inclination angles at 0°, 20°, and 30°. The results indicated that the combination of a 90° tube arrangement, a 25% baffle cut, and a 20° baffle inclination provided optimal performance based on the experimental setup. The results of this research provide insights into enhancing the efficiency of shell-and-tube heat exchangers, thereby addressing issues related to the complexity of the shell-side geometry.

Flow Characteristics Effect on Different Blades Number of Radial Fan

Kian Wui Chan — 2024-09-30

Radial fans are mainly used in industrial applications where working efficiency is of paramount importance. In order to examine the mass flow rate at the outlet for various configurations, three radial fan models with 12, 16, and 20 blades were modeled using ANSYS Fluent. The mass flow rate at the outlet of the 12-blade radial fan was determined to be 0.15897 kg/s. The mass flow rates for the 16-blade and 20-blade radial fans were 0.22092 kg/s and 0.22309 kg/s respectively, thus showing an increase in performance. The hypothesis of this study is therefore confirmed by the fact that as the number of blades increases, the spacing between them reduces ; hence, fluid flows at greater velocities, thereby enhancing the mass-flow rates. Verification and validation were established by comparing the results with those of other studies, which revealed a reasonable percentage error in each case. Furthermore, at the blade tips of the radial fan, the high static pressure, in conjunction with the radial velocity, reduces the vibration rates.

Wear-Preventive Characteristics of a Lubricating Bio-Fluid Using a Four-Ball Method

Mohamad Mazwan Mahat — 2024-10-01

This project studies the tribological performance of blended coconut oil as an environmentally friendly lubricant using a four-ball experiment. There has been growing concern over the use of mineral oils as lubricants in environmental issues such as soil and water pollution due to their persistence and potential to leach harmful chemicals into the environment. Several studies have been conducted on using coconut oils as alternatives to industrial gear oil; however, limited research has been conducted, especially regarding the different concentrations of blended coconut oil. Therefore, the tribological characteristics of lubricants with different ratios of Industrial Gear Oil VS 220 and coconut oil (5%, 10%, 15%, 20%, 25%, and 30%) were experimentally tested. The coefficients of friction and wear-preventive characteristics were evaluated with control based on the ASTM D4172 standard. Additionally, six (6) samples were blended using the sonication technique with the help of bench-top ultrasonic cleaner (DELTA). Hence, the result clearly indicates that 30% exhibited a lower friction coefficient (0.055) than 10%, which showed the highest value at 0.09. The surface morphology of the worn surfaces was observed using an Olympus Metallurgical Microscope. Under microscopic analysis, the 30% oil concentration yielded a smaller scar diameter than the other concentrations. As a result, increasing the mixed coconut oil concentration in the blend, specifically to 30%, resulted in a noticeable improvement in tribological performance. This included a reduction in the coefficient of friction and a decrease in the scar diameter compared with the other samples, suggesting that higher concentrations of coconut oil can enhance the lubricant’s environmental friendliness and performance in industry.