Applied Mechanics and Materials Vols. 592-594

Abstract: In-Situ Combustion (ISC) thermal Enhanced Oil Recovery (EOR) methods are aimed at increasing the oil recoveries of heavy oil reserves that are expected to play an instrumental role in near future in meeting the world’s energy demand. The complex multiphase heat and reactive mass transport necessitate a clear understanding of thermal and kinetic models used in modeling of ISC process. A finite difference based numerical analysis is carried out on heat loss and selective productions of light oil components during ISC, which showed a significant effect on peak temperature, thermal front propagation and the corresponding production rates dictating the performance of ISC process.

Abstract: The performance of an Earth-Air Heat Exchanger (EAHE) system to be operated in climatic and soil conditions prevailing in the Indian district of Nagpur is modeled numerically. To do so, a CFD model is developed in ANSYS Fluent 12.1. The validation of the CFD model is carried out using data obtained from published literature and good agreement is established between the simulation results and published experimental data. An earth pipe of length 60 m and internal diameter 0.1 m is chosen for validating the model and this validated model is used to further investigate for three different lengths of the pipe - 40 m, 35 m and 30 m. The 3-dimensional flow field through the earth air heat exchanger is studied numerically by solving the appropriate governing equations namely: continuity, momentum and energy equations and a finite volume CFD code is employed for solving the same. An air inlet velocity of 2 m/s is maintained and the inlet temperature was varied between 308.1 K and 315 K for each chosen length. The decrease in temperature and flow distribution along the pipe length is plotted.

Abstract: Modern internal combustion (IC) engines employ a variety of injection techniques for preparing a combustible mixture of fuel and air. In a fuel injection-based system, the vaporization of the atomized hydrocarbon fuel droplets has significant influence on engine performance and emissions. The entropy generation associated with droplet vaporization is particularly important as it is directly related to the destruction of exergy i.e. the potential to produce useful work. Since a fuel spray could involve millions of droplets, solving the entire set of governing equations for individual droplets in a spatiotemporally discretized domain is impractical. The present work explores the utility of a simple phenomenological model in predicting the entropy generation history. The results indicate that this model ensures computational efficiency without much sacrifice in accuracy.

Abstract: Refrigeration plays an important role in developing countries, primarily for the preservation of food, medicine, and for air conditioning. Conventional refrigeration systems are using Freon as refrigerant. As they are the main cause for depletion of ozone layer, extensive research work is going on alternate refrigeration systems. Vortex tube is a non conventional cooling device, having no moving parts which will produce cold air and hot air from the source of compressed air without affecting the environment.

Abstract: The objective of the present study is to investigate the performance of solar collector with serpentine shape of heat pipe and water-ethanol as a working fluid. Serpentine shape is easy of manufacturing and also to reduce cost of manufacturing. In this work, heat pipe is made from copper tube having ID 10mm and OD 12mm.The tube is bent in serpentine manner and filled with Water-ethanol as a working fluid with 70% filling ratio. The length of evaporator, adiabatic and condenser section was 480mm, 50mm and 65mm respectively. The test is conducted for coolant flow rate 4.5 kg/hr different angle of collector 20°, 31.5°, 40°, 50°, 60°. Result shows that water-ethanol collector gives better performance than collector with water as a working fluid. Maximum efficiency is observed at 31.5° inclination.

Abstract: An experimental investigation was conducted to study the heat transfer and pressure drop characteristics of an array of divergent straight minichannels (DSM) and was compared with straight minichannels (SM). The experiment was conducted in hydro dynamically developed and thermally developing laminar and turbulent regimes. The minichannel heat sink array consisted of 15 rectangular channels machined on a 30x30mm² and 11mm thick Aluminium substrate. Each minichannel was of 0.9mm width, 1.8mm pitch and a depth of 1.3 mm at entrance and 3.3 mm at exit for increasing the cross sectional area. DI water and 0.5% and 0.8% volume concentrations of Al₂O₃/water nanofluid were used as working fluids. The Reynolds number was varied from 1000 to 3500; and the heat flux was maintained as 45kW/m². It was observed that the heat transfer performance of the DSM channel was higher than that of the SM channel.

Abstract: This study aims to investigate the influence of inclination angle and concentration of nanoparticles on the improvement in heat pipe thermal efficiency. Spherical shaped, 40 nm size CuO nanoparticles are used in this study and its physical and thermal chracteristics are investigated. The results are compared with a heat pipe using DI water at horizontal position.The thermal efficiency is improved by increasing the tilt angle and mass of particles dispersed in DI water. The improvement in thermal efficiency obtained are 20.59, 35.92 and 32.57% respectively for 0.5, 1.0 and 1.5 wt% of CuO nanofluids and 60° inclination angle.

Abstract: Flow mal-distribution is defined as the non-uniform fluid flow distribution among the parallel channels having a common header. Flow mal-distribution is present in every header channel assembly. This mal-distribution has a significant effect on the performance of the heat exchanger by increasing the pressure drop and affecting the heat transfer characteristics. However, in designing a heat exchanger, a uniform flow distribution in each channel is assumed. The present work attempts to reduce the flow mal-distribution in a cross flow heat exchanger. A numerical analysis is done using a commercial code ANSYS FLUENT 3D and the results are validated experimentally. A parametric study is done by changing the size of the channels within the heat exchanger so as to reduce the flow mal-distribution. The effect of varying channel size on flow mal-distribution and pressure drop across the heat exchanger is studied and a geometry with reduced flow mal-distribution is found.

Abstract: The effects of Oxygen Enriched Combustion Technology in a single cylinder DI Diesel engine based on performance tests and analysis using Data Acquisition System has been studied in this thesis. This experiment involves the use of zeolite 13X molecular sieves to adsorb nitrogen from air. Pressure Swing Adsorption method is used for controlling the adsorbing and regeneration cycles of Zeolite 13X. It is a compact apparatus which is safe and feasible to fit in CI engine driven automobile. Increasing the oxygen content in the air leads to faster burn rates and increases the combustibility at the same stoichiometry. The Specific power output increases as the thermal efficiency of the engine increases due to the above stated factors. The power produced increases with oxygen enrichment.

Abstract: The tube to tubesheet joint in a heat exchanger is one of the most critical joint and it has to meet stringent requirements as it provides the main barrier between the tube side and shell side fluids of heat exchanger. This paper discusses the various kinds of tube to tubesheet joint in heat exchanger, joint configuration adopted in PFBR IHX, structural analysis of IHX, axial load distribution in tube rows and experimental verification in order to evaluate allowable strength of tube to tubesheet joint. In IHX, tubes in outer rows are under tension and maximum stresses are below the allowable stresses in the tubes. Detailed experimental investigations result shows that the rolled and welded joint is stronger than the basic strength of the tube material. However, the allowable tensile strength of the joint under mechanical loading considered is 0.95 times the allowable value for tubes as per ASME.