Some Studies on life of Track Pin Rubber Bushes .

Track pin an important component in the tracks of heavy armoured vehicles is made of steel surrounded by rubber bush. This construction enables the pin to transmit the torsional loads. As the failure of track pin makes the vehicle immobilised, it is important to ensure a specified life for these pins. As the pin is made of rubber and steel, the theoretical studies become difficult. An attempt has been made to find out the parameters that influence the life of track pins. A finite element method is used to estimate the stresses in the rubber. The temperature rise due to the torsional loads, computed using the energy equation is found to be 64.86 °c for 1800 s at a speed of 30 km/hr. close to that obtained from actual field measurements

Computational methods in Flipchip assembly.

Flip chip technology, in the book edited by Lau (Lau, 1995) is defined as placing a chip to the substrate by flipping over the chip so that the I/O area of the chip is facing the substrate. By flipping over the chip, the interconnection between the chip and the substrate are achieved by conductive "bumps" placed directly in between the die surface and the substrate. Therefore, the whole chip surface can be utilized for active interconnections and at the same time, eliminates the need for wire bonding

Effects of Radiation and Cold Wall Temperature Boundary Conditions on Natural Convection in a Vertical Annular Porous Medium

This paper deals with the numerical solution for natural convection in a vertical annular porous medium for various cold wall temperature boundary conditions and radiation parameters. The heat transfer is assumed to take place by convection and radiation. The inner wall (hot wall) of the annulus is maintained at an isothermal temperature while the outer wall (cold wall) is subjected to different temperature conditions. The temperature conditions maintained at the cold wall are evaluated for uniform as well as non uniform temperatures. The fluid is assumed to obey Darcy’s law. The governing partial differential equations are non-dimensionalised and solved by finite element method. The porous medium is discretised with unstructured triangular elements. The effects of radius ratio and Rayleigh number on the Nusselt number and Sherwood number are investigated on the annulus for different temperatures at cold wall. The effects of radiation on flow patterns, temperature distribution and concentration distribution are discussed. The results reveal that the Nusselt number and Sherwood number at cold wall decrease with the increase in radius ratio, whereas they increase with the radius ratio at hot wall for different temperature boundary conditions at the cold wall. Temperature cold wall conditions have pronounced effect on the Nusselt and Sherwood number

Effect of ambient heat-in-leak and longitudinal wall conduction on a three-fluid parallel flow cruogenic heat exchanger

Papers presented to the 11th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 20-23 July 2015.A three-fluid parallel-flow cryogenic heat exchanger, involving two thermal interactions, is investigated for the effect of ambient heat-in-leak and longitudinal wall conduction, using FEM for four different flow arrangements. The three fluids are referred to as hot, cold and the intermediate fluids. Seven non-dimensional parameters inclusive of those to account for ambient heat-in-leak and longitudinal wall conduction are defined to present the results.am201

Influence of Heat Input, Working Fluid and Evacuation Level on the Performance of Pulsating Heat Pipe

An experimental study on pulsating heat pipe (PHP) is presented in this work. A closed loop PHP with a single U turn is fabricated and tested. The transient and steady state experiments are conducted and operating temperatures are measured. The experiments are carried out for different working fluids, heat input and for different evacuation levels. The derived parameters include thermal resistance and heat transfer coefficient of PHP. The results of these experiments show an intermittent motion of the working fluid at lower heat input. The temperature difference between evaporator and condenser at steady state is found lower for acetone compared to water, ethanol and methanol. Lower value of thermal resistance and higher value of heat transfer coefficient are observed in case of acetone compared to water, ethanol and methanol. Lower values of temperature difference between evaporator and condenser and thermal resistance and higher value of heat transfer coefficient are observed at atmospheric conditions of operation of PHP compared to evacuation conditions. The Power Spectral Density Analysis is also carried out on the results of these experiments using FFT technique to analyse the pulsating motion of the fluid in a PHP. In the Power Spectral Density analysis, the frequency distribution of temperature variation in PHP was observed over a wider range, signifying the periodic motion in the fluid flow of the liquid slug and vapour plug. This characteristic frequency corresponded to the characteristic time for a couple of adjacent vapour plug and liquid slug passing through a specific local wall surface in a PHP

Buoyancy Driven Heat Transfer in Cavities Subjected to Thermal Boundary Conditions at Bottom Wall

Natural convection in cavities is studied numerically using a finite volume based computational procedure. The enclosure used for flow and heat transfer analysis has been bounded by adiabatic top wall, constant temperature cold vertical walls and a horizontal bottom wall. The bottom wall is subjected to uniform/sinusoidal/linearly varying temperatures. Nusselt numbers are computed for Rayleigh numbers (Ra) ranging from 103 to 107 and aspect ratios (H/L) 0.5 and 1. Air is taken as working fluid (Pr = 0.7). Results are presented in the form of stream lines, isotherm plots and average Nusselt numbers. It is observed from this study that the uniform temperature at the bottom wall gives higher Nusselt number compared to the sinusoidal and linearly varying temperature cases. The average Nusselt number increases monotonically with Rayleigh number for both aspect ratio 1 and 0.5 for bottom wall and side walls. For the case of aspect ratio 1, the average Nusselt number for a given Rayleigh number increases at the bottom wall compared to aspect ratio 0.5. However, the average Nusselt number increases as the aspect ratio decreases from 1 to 0.5 for side wall except for uniform temperature case

Computational Methods In Flip Chip Assembly.

Flip chip technology, in the book edited by Lau (Lau, 1995) is defined as placing a chip to the substrate by flipping over the chip so that the I/O area of the chip is facing the substrate. By flipping over the chip, the interconnection between the chip and the substrate are achieved by conductive "bumps" placed directly in between the die surface and the substrate. Therefore, the whole chip surface can be utilized for active interconnections and at the same time, eliminates the need for wire bonding

Effect of axial wall conduction and ambient heat-in-leak on the performance of a two-fluid counter-flow cryogenic heat exchanger, using finite element method

Papers presented to the 11th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 20-23 July 2015.A two-fluid, single-pass, counter-flow, cryogenic heat exchanger is investigated for the effect of ambient heat-in-leak to both the fluids and axial conduction in the wall separating the two fluids. In most cryogenics applications, the performance of heat exchangers deteriorates significantly due to heat-in-leak from the ambient and axial wall conduction. Here a small, counter-flow heat exchanger, of the type used in Joule-Thomson refrigerators, experiencing heat-in-leak to both hot & cold fluids, and axial wall conduction, is analyzed adopting the finite element method. Five non-dimensional parameters, including those to account for ambient heat-in-leak and axial wall conduction are defined to present the result. The effect of these parameters on the heat exchanger performance has been analyzed. The set of non-dimensional governing equations for hot fluid, cold fluid and the wall are obtained by energy balance. These governing equations are solved by FEM using Galerkin’s method.Validation is carried out by comparing the results obtained using the present methodology with those published in the literature for limited parameters. The excellent match between the two validates the solution methodology used. The effect of ambient heat-in-leak and axial wall conduction are studied for their effect on the fluid temperature profiles. Ambient heat-in-leak and axial wall conduction are found to increase the hot fluid exit temperature. The effect of axial wall conduction is found to be more concentrated towards the heat exchanger ends. Further, the effect of ambient heat-in-leak and axial wall conduction and varying non-dimensional parameters are studied for their effect on the hot fluid effectiveness and performance degradation.The authors wish to thank Dr. K.N.B. Murthy, Director, PESIT, Dr. K.S. Sridhar, Principal, PESIT and Department of Mechanical Engineering, PESIT, Bangalore, for the support and encouragement extended for this research work.am201

THERMAL PERFORMANCE PREDICTION OF PLASTICS BALL GRID ARRAY (PBGA) USING ARTIFICIAL NEURAL NETWORK

Artificial Neural Network (ANN) based on feed-forward backpropagation model is used  to predict junction temperature in PBG A package. The limited results obtained from FEM (using IDEAS software) are used to train the neural network. The effect of source power, substrate and mold compound thermal conductivity, die size, substrate thickness and air velocity on junction temperature and thermal resistance has been investigated using ANN.  The predicted junction temperature using ANN agrees closely with the prediction from FEM. ANN method takes a small fraction of the time and effort compared to that required by HEM for prediction

Finite element simulation of transient laminar flow past a circular cylinder and two cylinders in tandem

International Journal of Numerical Methods for Heat and Fluid Flow106560-580INMF