Engineering Headway Vol. 8

Abstract: The literature about various modifications to the vortex generators as passive techniques and some combined techniques was discussed numerically and experimentally. In general, all vortex generators have a good coefficient of thermal performance compared to a plain tube. Most vortex generators don’t consume any amount of energy to perform their function, so can be considered a good tool to enhance the thermal performance coefficient in industrial applications, but they have the disadvantage of high pressure drop. When using vortex generators in two phase flow accelerated the process of transition between phases pattern in addition to increasing heat transfer. The inserted twisted tapes have a low pressure drop and good heat transfer efficiency, resulting in a thermal performance factor of 1.6.In addition, the easier to manufacture where can be changed in size and shape in proportion to the place of use inside the tubes also having a low cost, and do not consume any amount of energy to perform its function, the hybrid methods can be used with it, such as a twisted tape with nonfluids, which had proven effective in thermal performance coefficients, but their disadvantages include the high cost and risk of dealing with these materials ,bubble injectors can also be used, despite the fact that they require energy to operate. So, the twisted tapes inserted can be considered a best tool to be used in enhancing the thermal performance coefficient in various Industrial fields.Based on the reviewed literature, it was determined that the following research is limited and could garner more attention in the future: multiple coaxial cross-twisted tapes with different perforations, and twisted tapes with variable cross-section, typical twisted tapes with regular wavy edge, hybrid methods such as nanofluids and twisted tape can be used in multiphase flow.

Abstract: A numerical simulation of the effect of rotation on mixed convection laminar flow with separation and reattachment length is studied. The channel is subjected to span-wise Rotation. The working fluid was air with the prandtl number of 0.71. The governing equations are solved with a finite element-based commercial solver, COMSOL Multiphysics. The influence of the Reynolds number and angular velocity Ω on the fluid flow and heat transfer characteristics is numerically studied. Range varies Reynolds number (100 ≤ Re ≤ 500), Richardson number (0.1 ≤ Ri ≤ 10), and angular velocity Ω (0, 10, 20, 30). The Nusselt number, pressure drop, recirculation length, and total flow rate were calculated. The calculated results span a wide parameters set, particularly from low rotational speed to high rotational speed. The Nusselt number, pressure drop, and patterns are shown. When comparing the results of the standard BFS case with the rotating BFS case in a step facing backward, the Heat Transfer Enhancement was 3% present obtained for rotation of Ω=30 at the Reynolds number Re=500.

Abstract: The enhancement of thermal stratification in solar storage tanks is a crucial aspect of advancing solar energy technology. This study presents an experimental investigation conducted on a vertical cylindrical hot solar water storage tank operating in a dynamic mode, involving simultaneous charging and discharging. The experiment aims to assess the impact of varying inlet water flow rates (4, 6, 8, 10 L/min) on thermal stratification within the tank and explores strategies to mitigate heat losses to the environment and minimize mixing effects caused by the inlet fluid flow. The experimental setup incorporates insulation and an inlet port diffuser section to optimize the distribution of inlet water during the charging and discharging states. The results reveal that the utilization of an inlet port diffuser significantly improves thermal stratification by reducing heat losses and minimizing mixing effects, as evidenced by improved Richardson numbers. Additionally, this study contributes to the development of a compact solar domestic hot water (SDHW) solution.

Abstract: Microchannels based on Micro Electromechanical Systems (MEMS) have garnered a great lot of interest over the past 40 years from the fields of microfluidics and biomedicine. In order to address the problem of heat dissipation in incredibly small integrated circuits with up to 790 W/cm² of huge heat dissipation capabilities, Tuckerman et al. [1] first proposed the microchannel heat rejection idea in 1981. These channels are typically at the microscale, with characteristic dimensions on the order of micrometers 10^-6 m or smaller as shown in Figure 1 [2]. These channels often exist at the microscale and have characteristic diameters of micrometres 10^-6 m or less. Microchannels display distinct fluidic behaviour as a result of their small size. Because the flow is normally laminar and the Reynolds number is low, the flow pattern is predictable. Capillary forces and other surface forces become comparatively more important. As a result, fluid behaviour in microchannels is greatly influenced by surface wetting characteristics and channel surface roughness.

Abstract: Scientists from a variety of fields have joined forces to study a world so small that it cannot be seen with the naked eye, not even under a light microscope. That is the domain of nanotechnology, the universe of atoms and nanostructures. Anything between 1 and 100 nm in size is generally considered to be within the purview of nanotechnology, despite the occasional disagreement among experts regarding precisely what is included in the nanoscale. That is not the atomic scale and the microscale is still larger. This paper will define nanotechnology and discuss its potential future applications. The application of nanoparticles in one of the mechanical engineering field's most significant uses will also be reviewed. The Vapor Compression Refrigeration System (VCRS) uses nanobased refrigerants to deliver a better, faster cooling process with less power consumption. resulting in the provision of a healthier environment and a more effective system.

Abstract: A four-pass cross-flow heat exchanger was developed and manufactured in this practical study for two types of tubes: smooth and triangular finned tubes. The length of the tube is 250 mm, for a smooth tube the inner and outer diameter (19, 21 mm), and (19, 21 and 24 mm) the inner, outer diameter and the fin root for the finned tube respectively. Water is used as a hot fluid inside the tubes and air is used as a cold fluid outside the tubes. Inlet hot fluid temperatures were 50, 60, 70, and 80 °C, with three air speeds (1, 2, and 3 m/s), and volumetric flow rate (2, 3, 4, and 5 l / min) held steady at 25 ° C. The finned tube outperformed the smooth tube in terms of heat transfer rate, heat transfer coefficient, total heat transfer coefficient, and effectiveness, according to the findings.

Abstract: A conical disc arranged in different stacks parallel, or series works as a compression spring used in different machine applications. This work focusing on presenting a comparison between theoretical calculation with experimental performance of single spring and their stacked. This comparison with cold stamping manufactured based on spring force and spring rate constant related with deflection. The spring design is chosen according to Belleville spring standard depending on sheet thickness of the selected material Carbon steel C55S-1/1204. Results experimental force for a single spring started high to about (0.2 mm) deflection, then reduced less than theoretical results, with a deviation (32.5 %). The parallel stacked of springs show, the force increased with increasing numbers of discs in spring stack, without clearly affecting deflection of stack in theoretical, but the experimental have (13.5%) variation for two springs and (14.6%) for three discs. While, the series stacked, show the spring deflection increased with increasing numbers of springs in the stack, without clearly affecting the spring force, with a variation of (38.5%) for two spring and (10%) for three discs. Finally, the spring rate increased with increasing deflection till reaching flatness, where the theoretical calculations show higher than the measured experimentally in about (31.5%).

Abstract: In this research, a main matrix has been derived from the stress components in the inclined plane with an angle θ that calculates the normal stresses and shear stress in the inclined plane to be used in calculating the main stresses and the maximum shear stress in one step, this is done using the principal stress angle which is calculated from known stress compounds. As well as calculating the maximum shear stress after using the correction factor. The inverse of this derived matrix can be used to calculate the stress compounds through the known principal stresses and this applies to the components of the principal strain and strain, and the maximum shear strain. All this is done through MATLAB simulation Keywords: Normal Stresses and Strains, Shear, Principal Stresses, max. Shear Stress

Abstract: This research presented a numerical assessment for a a selected theoretical design of single and stacked Belleville spring taken into consideration the strength behaviour. Theoretical and numerical analysis focused on two main factors which are the spring force and the variation of the stress at a specific locations across the spring section related to the deflection. This research chose the spring design dimensions according to the Belleville spring standard. The numerical simulation are done by employing ANSYS APDL 2018 software based on the same design and selected material properties. The comparison between the finding shows a good match with deviation less about, where the variation for a single spring being less than 10.9%, and the deviations being about 11.8% and 12.8% for two and three parallelly stacked discs. On the other hand, the divergence was approximately 12.4% and 12.2% for two and three discs stacked in series. The stress distribution results across the spring section shows at the final deflection of (1.15 mm), the maximum von Mises stress is concentrated at the upper surface of the inner hole of the spring, this stress is reduced in value when goes deeply through the thickness of the disc, till reach the minimum value at the middle section of the thickness.