Applied Mechanics and Materials Vols. 592-594

Abstract: A two-dimensional model is presented in this article to study the transient radiative transfer phenomena involved in a participating medium subjected to short pulse collimation. The model assumes the medium bounded by diffusely emitting and reflecting boundaries, one of the boundaries is irradiated with a short pulse collimated beam. The finite volume method is applied to solve the transient radiative transfer equation governing the physical phenomena. The fully implicit scheme is used to discretize the transient term. In the proposed approach, intensity can directly be evaluated by solving the governing transient radiative transfer equation. The effects of scattering albedo and emissivity on the transmitted and reflected flux are studied. The performance of two different spatial schemes: STEP and CLAM are also been tested. It is seen that the CLAM scheme gives results to a greater accuracy and hence, correctly predict the speed of photon whereas STEP scheme over predicts the same.

Abstract: This paper deals with the modeling and analysis of drying of biomass in gasification. Biomass is a potential alternative for fossil fuels like coal, oil etc., to sustainably meet the increasing energy needs of the world. The different methods of conversion of biomass are anaerobic and thermo chemical conversion. Since, thermo chemical conversion is a reliable one we opted to choose it. The paper deals more with the analysis of the biomass drying and heat transfer towards the inlet air for combustion. The proposed work increases the efficiency of the drying chamber by increasing the temperature of the inlet air and also it analyses on increasing the effectiveness of the heat exchanger by changing the input values by simulation. Simulation is the initiation of the real world process or system overtime. It is also used with the scientific modeling of human system to gain insight. Here simulation is carried out using MATLAB. It is user friendly and adds real time values in coding.The results are plotted in the graph shows the comparative performance before and after preheating.

Abstract: The present paper reports results of simulation studies on combined conduction – convection – radiation from two dimensional electronic board equipped with three discrete non identical heat sources. The three non identical heat sources are located across the board. The heat generated in the three heat sources is conducted across the board subsequently getting dissipated by convection and radiation. Air, a radiatively transparent medium, is considered to be the cooling agent. The governing partial differential equations for temperature distribution in the entire computational domain are obtained by appropriate energy balance between the heat generated, convected and radiated. The non linear partial differential equations deduced as above are discretized using finite difference method. The resulting algebraic equations are solved using Gauss - Seidel iterative method. A computer code in C⁺⁺ is written to solve the problem. A thorough energy balance test and grid study has been performed to freeze on appropriate grid size. The effect of thermal conductivity, surface emissivity and convection heat transfer coefficient on local temperature distribution and maximum temperature distribution of the electronic board are demonstrated exhaustively. Keywords: Surface Radiation, Conduction, Convection, Electronic Board, identical Heat sources.

Abstract: Now a day’s different types of solar flat plate collectors are in use. Out of which only few type of collectors proved their performance by producing better results of expected level. In this paper a new set of collectors are combined as mean to improve performance of series SFPC collectors available in market now a days. In such new combination a collector with reduced overall loss coefficient was used to improve the efficiency of the existing system. New collector with zig-zag flow pattern gives a slight change in flow path. Thus the objective of this experimental analysis is to improve efficiency with new set of series FPC by comparing with existing series FPC. Experimental results obtained give better and higher results suggested by theoretical analysis.

Abstract: Crankshaft is one of the most important components of an IC engine. Crankshaft should be checked carefully to ensure that its design is fully optimized. The main objective of this paper is to perform the static analysis on four cylinder engine crankshaft to find out its static strength and the maximum stress zone and analyzing the different methods for the optimization of crankshaft in terms of weight, stress and cost reduction. A three dimensional model of four cylinder engine crankshaft is prepared corresponding to actual conditions in Catia V5 software, static analysis is performed using Ansys under extreme operating conditions and the improvement methods for the optimum design are analyzed in terms of geometric improvement, appropriate material selection and methods used for manufacturing of crankshaft.

Abstract: Missiles fly at supersonic and hypersonic speeds. Airframe forms the aerodynamic shape of the missile and houses several components essential for mission with suitable structural supports. The missile airframe is subjected to high rate of heating caused by kinetic heating due to very high vehicle speed. Heat transfer analysis of the missile airframe structure is required to be performed for wall temperature predictions to select the material of missile construction with suitable wall thickness and also to check design adequacy for ensuring the safe operation in the severe thermal environment experienced during flight. This paper describes the methodology of evaluation of heat flux distribution over missile wall, prediction of missile wall temperature distribution considering airframe as heat sink and validation of the methodology against flight data. Heat flux has been estimated using classical engineering methods for both stagnation as well as off-stagnation regions including the effect of angle of attack, rarified flow, thermal radiation and solar heating. Transient three dimensional heat transfer analysis with convective and radiative boundary conditions has been carried out for predicting the missile wall temperature profiles. Parametric study has been carried out, considering various parameters such as material of construction, thickness and time duration. The prediction methodology has been validated and a close match is observed between the predictions and flight data.

Abstract: This paper proposes a simplified theoretical model of Pulsating Heat Pipe (PHP) employed in a vapour compression refrigeration system. The model developed is mainly based on well known physical equations and partially based on empirical correlation. The present theoretical investigation of PHP is focused to explore its suitability as a heat exchanger in the condenser of vapour compression refrigeration system. A parametric analysis is carried out to design the vapour compression refrigeration system with PHP as the condenser. The performance of the system is evaluated for different PHP diameters, working fluids, evaporator and condenser temperatures and evaporator and condenser lengths. The effect of super heating and sub cooling the refrigerant are also studied. The results showed an increase in performance of the system at higher evaporator and lower condenser temperatures. The best results are obtained with R-12 as the working fluid. Also there is an increase in the COP of the system due to decrease in pressure drop in the condenser.

Abstract: Missile airframe experiences large variations in wall temperature along the circumference due to high angle of attack, especially at hypersonic speeds, which leads to large thermal stresses and bending loads. Such a situation with large wall temperature variations occurs due to high angle of attack during flight. Thermal design of the airframe involves the estimation of local flow parameters and heat flux distribution. Kinetic heating analysis has been carried out for the prediction of heat load distribution on missile airframe considering hypersonic flow with high angle of attack for a particular flight trajectory. Out of a set of possible flight trajectories, a trajectory producing minimum circumferential variation in wall temperature, as concluded through kinetic heating analysis, is finalized. Transient three dimensional heat transfer analysis of the airframe is carried out for prediction of wall temperature distribution for proper selection of material of construction of airframe so that it retains its strength at elevated temperatures. Parametric study has been carried out considering various combinations of airframe wall thickness in presence of external thermal protection coating and internal insulation for the finalized trajectory. Based on the present analysis, airframe configuration having axially variable wall thickness corresponding to the selected flight trajectory is finalized. The validation of the methodology adopted for the analysis has been carried out with respect to airframe temperature data acquired during flight.

Abstract: Latest trend in increasing the performance characteristics of precision machines is reducing error in machines. Today research is focused on Machine tool accuracy. The effect of thermal error contributes to major part of 70% of volumetric error. The present study aims to establish a new compensation method for CNC Turning centre. Selection of proper temperature variables is a great task in thermal error compensation. In this paper 3 thermal process variables namely spindle speed; temperature and time are used to create thermal error models. Using ANSYS simulation experiments are created.

Abstract: Increasing energy consumption, high cost and exhaustible nature of fossil fuels and their impacts on environment have increased interest in production of hydrogen from thermochemical cycles by harvesting energy from renewable energy sources in the present scenario. By using thermochemical cycles the large quantity of hydrogen production is possible. The main thermochemical cycles out of all reference cycles are Cu-Cl, Zn-ZnO, S-I, Ca-Br and Fe-Cl.