Journal of Engineering Research

Numerical Thermohydraulic Analysis of Flow Boiling in Geometrical-Modified Microchannels

2025-04-08T16:44:04+00:00

One of the major issues of flow boiling in microchannels is ensuring adequate management of thermohydraulic instabilities which severely impact the system’s efficiency in terms of pressure drop and heat transfer coefficient (HTC). The current study focuses on microchannels with geometric modifications, varying inlet conditions and geometry dimensions with view on mitigating thermohydraulic instabilities and improving overall performance. The study used Computational fluid dynamics (CFD) software - ANSYS Fluent - with the Volume of Fluid (VOF) model to simulate the flow boiling in microchannels. The flow is transient and laminar in a 3-D domain with water (H₂O-liquid) as working fluid. The flow and heat transfer characteristics in baseline rectangular are compared with constricted inlet-, and expanding inlet microchannels. Pressure drop, heat transfer coefficient, Nusselt number, and frictional factor are studied and visualized across varying mass fluxes 3000 – 7000 kg/m²s (for all microchannels) and angle of divergence 0.2^o – 1^o (for the expanding inlet). The expanding inlet microchannel showed a better thermohydraulic performance, having a 63.25% increase in HTC and a 64.16% reduction in pressure drop compared to the baseline design, highlighting its potential for enhancing thermohydraulic stability. Also, the angle of divergence gave more insights to the expanding inlet microchannel with 0.2 ^o having a better performance. These findings solidify the critical role of geometric modifications in optimizing microchannel performance, with the expanding inlet design resulting as the configuration for a better heat transfer performance and pressure stability, thus giving valuable insights for advancements in microchannel design and flow boiling applications.

Numerical Prediction of Flow Recirculation Length Zone in an Artery with Double Stenosis at Low and High Reynolds Numbers

2025-04-11T19:29:56+00:00

This work presents simulation of arterial stenosis utilizing ANSYS (Fluent) Computational Fluid Dynamics (CFD) software package for better understanding of blood flow dynamics and to estimate the risk of complication. The aim of the paper is to investigate and study the effects of low and high Reynold’s number on recirculation zone length in arteries with varying levels of double stenosis. Blood flow was numerically simulated to predict the recirculation zone length and wall shear stress. An artery with double stenosis was studied and for the purpose of this investigation, stenosis levels of 15/15%, 75/75%, 15/75%, 75/15%, 15/60%, 20/60%, 45/60% 60/60%, and 75/60% in terms of proximal and distal stenosis are studied over the Reynolds number ranging from 150 to 3000. Blood was a Newtonian fluid flowing as a steady, three-dimensional, incompressible fluid. The velocity flow streamlines, and wall shear stress contours are presented. Results revealed that when varying both distal and proximal stenosis, as Reynolds number increases, recirculation zone length decreases in lower levels of stenosis between 15/60% and 45/60% while it remains relatively constant for higher levels of stenosis 60/60% and 75/60%. It was also revealed that when varying both distal and proximal stenosis, as Reynolds number increases, maximum wall shear stress increases gradually at lower levels of stenosis with almost equal values. At higher levels of stenosis, there was rapid increase in maximum wall shear stress as Reynolds number increases.

Investigation of the Properties of Sugarcane Bagasse Particle Reinforced Epoxy Matrix Biocomposites

2025-04-11T19:36:21+00:00

The stir casting technique was employed to produce sugarcane bagasse particle-reinforced epoxy matrix biocomposites. The microstructure, physical and mechanical properties of the composites were evaluated. The results obtained from the experiments revealed the presence of pores in the microstructure and distribution of reinforcing particles in the epoxy matrix. The control specimen possessed a density of 0.71 g/cm³ while specimens S4, S5 and S6 possessed the highest density of 0.93 g/cm³. Control specimen C1 demonstrated water absorption of 0.25 % while specimens S5 and S6 demonstrated the lowest water absorption of 0.19 %. Control specimen demonstrated the lowest tensile strength of 7.21 MPa whereas specimen S5 which contained 25 wt. % of bagasse particles demonstrated the highest tensile strength of 22.55 MPa. This is 213 % higher than that of the control specimen. Specimen S5 containing 25 wt. % of bagasse particles demonstrated the highest hardness value of 23.95 HV. The control specimen C1 demonstrated the highest impact energy of 4.87 J. The impact energy of the specimens decreased as weight percent (wt. %) of bagasse particles increased. The decrease in impact energy is suggested to be due to the presence of filler particles, which may represent points for localized stress concentration from which failure began.