M.K. Abdullah

Combustion in porous media and its applications – A comprehensive survey

The rapid advances in technology and improved living standard of the society necessitate abundant use of fossil fuels which poses two major challenges to any nation. One is fast depletion of fossil fuel resources; the other is environmental pollution. The porous medium combustion (PMC) has proved to be one of the technically and economically feasible options to tackle the aforesaid problems to a remarkable extent. PMC has interesting advantages compared with free flame combustion due to the higher burning rates, the increased power dynamic range, the extension of the lean flammability limits, and the low emissions of pollutants. This article provides a comprehensive picture of the global scenario of research and developments in PMC and its applications that enable a researcher to decide the direction of further investigation. The works published so far in this area are reviewed, classified according to their objectives and presented in an organized manner with general conclusions. A separate section is devoted for the numerical modeling of PMC.

Effect of piezoelectric fan height on flow and heat transfer for electronics cooling applications

Piezoelectric fan is used to remove the heat from the microelectronic devices, owing to their low power consumption, minimal noise emission and small in size. In the present study, a piezoelectric fan has been investigated to analyze the performance. The paper also discusses the capability of piezoelectric fan to cool the microelectronic device and its performance. The simulation and experimental investigations have been made for two different positions of piezoelectric fan i.e. vertical and horizontal positions. The Fluent 6.2.3 software which is a computational fluid dynamics (CFD) code has been used in the simulation to predict the heat transfer coefficient and the flow fields. In the experimental set-up, two heaters in line arrangement have been used in the set-up. The flow measurements have been carried out by using the particle image velocimetry (PIV) system at different piezoelectric fan height. The heat transfer coefficients have been plotted and compared with the experimental values. The simulation results obtained are found in satisfactory agreement with the experimental results.

Effect of Wing Deformation on the Aerodynamic Performance of Flapping Wings: Fluid-Structure Interaction Approach

Wing stiffness is very crucial in augmenting aerodynamic forces in flapping wing flyers. In this work, the effect of wing deformation was studied using three-dimensional numerical analysis (two-way fluid structure interaction), coupling the flow solver (FLUENT) and the structural (ABAQUS) solver via the MpCCI platform. Three different degrees of bending stiffness corresponding to rigid, flexible, and highly flexible case wings were investigated. Moreover, the wings were tested for both low Reynolds number (R=9,000) and high Reynolds number (R=40,000), at a flapping frequency of 9 Hz corresponding to an angle of attack (AoA) ranging from α=0 to 50°. The results of mean aerodynamic lift and drag coefficients showed good agreement between numerical and experimental findings. Also, the time-averaged lift-to-drag ratio reveals that the highly flexible wing exhibited the best overall aerodynamic performance when compared to the rigid and flexible wing.

Natural convection of discrete heating in a cavity filled by porous media for different aspect ratio

Numerical analysis is presented for buoyancy-induced natural convection from discrete heating inside a rectangular enclosure filled with porous media. The study has been made for Rayleigh number range of 10 - 1000 and aspect ratio of AH= 10, 4, 2 and 1. The two vertical walls are heated discretely on the right wall and cooled isothermally on the left wall respectively. The remaining two walls are adiabatic. The distribution of stream function was observed and temperature distributions are presented and analyzed. In addition, the present results are compared with previous researchers and show in good agreement.

Numerical Investigation on the Effect of Squeegee Angle during Stencil Printing Process

The high requirement of smaller size, lighter weight, and high performance Printed Circuit Board (PCB) in electronic packaging has contributed to the wide application of stencil printing for soldering process. However, during stencil printing stage contributes major concern compared to other stages in Surface Mount Technology (SMT). Unsuitable process parameters can cause the soldering defects that can lead to product failure in further processes in the production line. An investigation has been conducted to predict the real-time observation of solder paste Sn96.5Ag3.0Cu0.5 (SAC305) filling process into stencil apertures as well as print quality in stencil printing by using Computational Fluid Dynamics (CFD) approach. A 3-Dimensional stencil printing model was developed and simulated in ANSYS Fluent 17 of different angles. It is found that squeegee angle 60° to 80° has potential to obtain the good print quality of solder paste.

Numerical investigation of heat transfer in Plastic Leaded Chip Carrier (PLCC) packages in in-line arrangement

Plastic Leaded Chip Carrier (PLCC) package has been emerged a promising option to tackle the thermal management issue of micro-electronic devices. In the present study, three dimensional numerical analysis of heat and fluid flow through PLCC packages oriented in-line and mounted horizontally on a printed circuit board, is carried out using a commercial CFD code, FLUENTTM. The simulation is performed for three configurations such as 4PLCC, 8PLCC and 12PLCC under natural, mixed and forced convection modes with different inlet velocities and chip powers. The contours of average junction temperatures are obtained for each package under different conditions. It is observed that the junction temperature of the packages decreases with increase in inlet velocity and increases with chip power. Moreover, the increase in package density significantly contributed to rise in temperature of chips. Thus the present simulation demonstrates that the chip density (the number of packages mounted on a given area), chip power and the coolant inlet velocity are strongly interconnected; hence their appropriate choice would be crucial. Keywords: PLCC package, Thermal management, Numerical simulation, Average junction temperature