G.A. Quadir

Radiation and viscous dissipation effect on square porous annulus

The present study is carried out to investigate the effect of radiation and viscous dissipation in a square porous annulus subjected to outside hot Th and inside cold Tc temperature. The square annulus has a hollow section of dimension D×D at the interior of annulus. The flow is assumed to obey Darcy law. The governing equations are non-dimensionalised and solved with the help of finite element method. Results are discussed with respect to viscous dissipation parameter, radiation parameter and size of the hollow section of annulus.

Heat transfer in porous medium embedded with vertical plate: Non-equilibrium approach - Part A

Heat transfer in a porous medium embedded with vertical flat plate is investigated by using thermal non-equilibrium model. Darcy model is employed to simulate the flow inside porous medium. It is assumed that the heat transfer takes place by natural convection and radiation. The vertical plate is maintained at isothermal temperature. The governing partial differential equations are converted into non-dimensional form and solved numerically using finite element method. Results are presented in terms of isotherms and streamlines for various parameters such as heat transfer coefficient parameter, thermal conductivity ratio, and radiation parameter

Heat and mass transfer in porous cavity: Assisting flow

In this paper, investigation of heat and mass transfer in a porous cavity is carried out. The governing partial differential equations are non-dimensionalised and solved using finite element method. The left vertical surface of the cavity is maintained at constant temperature and concentration which are higher than the ambient temperature and concentration applied at right vertical surface. The top and bottom walls of the cavity are adiabatic. Heat transfer is assumed to take place by natural convection and radiation. The investigation is carried out for assisting flow when buoyancy and gravity force act in same direction.

Heat transfer in a conical porous cylinder with partial heating

The current work simulates the heat transfer across a porous medium fixed in an annular conical cylinder. The geometry is such that the lower part is conical annulus supporting a regular annular cylinder. The porous medium is fixed between inner and outer radius of conical annular cylinder. The inner radius until conical section is heated with constant temperature Th whereas the outer radius is cooled to isothermal temperature Tc such that Th>Tc . The heat transfer phenomenon in this case can be described by two coupled partial differential equations which are solved using finite element method by using 3-node triangular elements. The heat transfer characteristics in this case are quite different from other geometries being discussed in the literature. It is observed that the fluid flow is stronger in the conical section as compared to the cylindrical part of porous geometry. A very few isothermal lines penetrate into the cylindrical porous region as compared to that of conical section.

Thermal management of multi‐chip module and printed circuit board using FEM and genetic algorithms

Purpose – To determine the optimal chip/component placement for multi‐chip module (MCM) and printed circuit board (PCB) under thermal constraint.Design/methodology/approach – The placement of power dissipating chips/component is carried out using genetic algorithms (GA) in order to achieve uniform thermal distribution on MCM and PCB. The thermal distribution on the MCM and PCB are predicted using 2D‐finite element method (FEM) analysis. Different number of chip/component and FEM meshing size is used to investigate the placement of chips/components.Findings – The optimal placement of chip/component using GA is compared well to other placement techniques. The coarse meshing for FEM employed here is found adequate to carry out optimal placement of components by GA.Research limitations/implications – The analysis is valid for constant properties of MCM or PCB and steady state conditions. The chip/component size is limited to a single standard size.Practical implications – The method is very useful for practic...

Temperature cycling analysis for ball grid array package using finite element analysis

Purpose – The purpose of this paper is to discuss the capability of finite element analysis (FEA) in performing the virtual thermal cycling reliability test to evaluate the reliability of solder joints in a ball grid array (BGA) package.Design/methodology/approach – Thermal cycling test has been used to evaluate the reliability or fatigue life of the solder joints in BGA package using commercially available FEA software, ANSYS™. The effect of different temperature cycling condition is studied by applying different value of dwell time and ramp rate. Two types of analyses are used namely, the physics‐based analysis and the statistical‐based analysis. Two screening design methods namely, central composite design (CCD) and Box‐Behnken Matrix Design method are used to isolate the most important factors amongst six selected design variables. The optimization process is carried out using response surface methodology (RSM).Findings – It is observed that changes in ramp rate produce significant effect in solder fa...

Numerical investigation on the thermohydraulic performance of a shell-and-double concentric tube heat exchanger using nanofluid under the turbulent flow regime

ABSTRACT The heat transfer characteristics of water-based Al2O3 nanofluid flowing through the annulus-side of a shell-and-double concentric tube heat exchanger (SDCTHEX) are investigated numerically. The temperature-dependent thermophysical properties of the nanofluid and pure water were used. The heat exchanger is analyzed considering conjugate heat transfer from hot oil flowing in the shell and the inner tube to the nanofluid flowing in the annulus formed between the concentric tubes. The overall performance is assessed based on the thermohydraulic performance. The overall thermohydraulic performance of the SDCTHEX, expressed in terms of the ratio of the overall heat transfer rate to the overall pressure drop with the nanofluid flowing in the annulus, is lower than that obtained with water when compared at constant hot fluid mass flow rates and at different inner tube diameters.

Flow analysis for flip chip underfilling process using characteristic based split method

In this paper, an effort has made to analyze and numerically simulate the fluid flow in chip cavity using characteristic based split (CBS) method. Simulation methodology includes a solver for the fluid flow equations coupled with technique to keep track of the flow front. Solver uses general convection-diffusion equations and solves flow equations using CBS method in conjunction with finite element method (FEM). The fluid front tracking is carried out using volume of fluid (VOF) technique. The velocity field obtained from CBS scheme is used in pseudo-concentration approach to track the advancement of fluid front. A particular value of the pseudo-concentration variable is chosen to represent the free fluid surface demarcating the mold compound and air regions which can be tracked for each time step. Simulation has been carried out for a particular geometry of a flip-chip package. The results obtained are in good agreement with literature and experimental data

Numerical Simulation for the Aerodynamics of Vertical Axis Wind Turbine with Two Different Rotors Having Movable Vanes

Wind energy has seen a rapid growth worldwide. Wind turbines are typical devices that convert the kinetic energy of wind into electricity. Researches in the past have proved that Vertical Axis Wind Turbines (VAWTs) are more suitable for urban areas than Horizontal Axis Wind Turbines (HAWTs). In the present design of the VAWT, the power prodused depends on the drag force generated by the individual blades and interactions between them in a rotating configuration. Numerical simulation for the aerodynamics of VAWT with tow different rotors (Three and Foure blades ) having movable vanes are curred out. The For numerical simulation, commercially available computational fluid dynamic (CFD) softwares GAMBIT and FLUENT are used. In this work the Shear Stress Transport (SST) k-ω turbulence model was used which is better than the other turbulence models available as suggested by some researchers. The predicted results show agreement with those reported in the literature for VAWT having different blades designs.

Modeling for the Aerodynamics Analysis of the Four Blades Movable Vanes Type Vertical Axis Wind Turbine (VVAWT)

The power generated by a Vertical Axis Wind Turbine (VAWT) depends on the drag force generated by the individual blades and interactions between them in a rotating configuration. The present Analysis is on attempt to predict numerically the coefficient of drag and other aerodynamic parameters for a four blade Vane type Vertical Axis Wind Turbine (VVAWT) with different blades and vanes position. For numerical investigation, commercial available computational fluid dynamics CFD software GAMBIT and FLUENT are used. In this numerical analysis the Shear Stress Transport (SST) k-ω turbulence model is used which is better than the other turbulence models available as suggested by some researchers. The computed results show good agreement with published experimental results.