Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

Department of Thermal and Energy Engineering

Many cook stove programs implemented in South Asia and Africa were aimed at reducing fuel wood consumption and pollutants through the use of improved cook stoves. The research work presented in this paper is focused on evaluation of improved cook stoves with respect to thermal efficiency and emission levels. Since the type of biomass fuel varies in different geographical regions, the improved cook stoves must be compatible to use different types of fuel. The present research work is aimed at evaluating three types of forced draft cook stove with two types of biomass fuels. Water boiling tests were conducted to evaluate the stove performance with respect to efficiency and fuel flexibility. The findings of the study are used to evaluate the stove's performance with respect to fuel flexibility, efficiency and user acceptance. The performance results of three types of forced draft stoves tested with fuel wood and coconut shell are presented in this research paper. © 2012 Elsevier Ltd.

World University root node

School of Mechanical Engineering

Vellore Campus

Biomass and Bioenergy

Performance evaluation of three types of forced draft cook stoves using fuel wood and coconut shell

Pt doped TiO2 nanoparticles with different concentrations of Pt were prepared by sol-gel method. X-ray diffraction (XRD) study reveals that the samples have a homogeneous anatase phase tetragonal system and the lattice parameter analysis indicates that Pt ions substitute into the lattice of TiO2. The addition of dopant increases the growth of TiO2 grains, agglomerates them and shifts the absorption band of TiO2 from ultraviolet to visible region. The incorporation of Pt in TiO2 is also confirmed by fluorescence quenching and the fluorescence lifetime decreases as the volume fraction of Pt dopant increases. Open aperture Z-scan measurements done at 532 nm using 7 ns laser pulses show nonlinear absorption which arises from an effective two photon absorption process. The nonlinear optical properties are characterized by using fluence dependent transmittance measurements in order to reveal the optical limiting effects. It is found that the optical limiting performances of nanoparticles were greatly enhanced with increased concentration of Pt. © 2013 Elsevier Ltd. All rights reserved.

Physics

School of Advanced Sciences

Chennai Campus

Materials Research Bulletin

Investigation on the structural and nonlinear optical properties of Pt doped TiO2 nanoparticles

This paper presents the numerical investigation of double-diffusive mixed convective flow in an impermeable enclosed cavity. The uniform temperature and concentration is imposed along the vertical walls and the horizontal walls are considered as insulation. The flow behavior is analyzed when the top wall moves left side at a constant velocity (Uo) and the other walls kept remains stationary. Transport equations are solved using finite volume technique. The pressure and velocity terms are coupled by SIMPLE algorithm. The third order deferred Quadratic Upwind Interpolation for Convection Kinematics (QUICK) scheme and second order central difference scheme are applied at the inner and boarder nodal points, respectively. The present numerical simulation is compared with the reported literature and found that are in good agreement. The heat and mass transfer results are presented in the form of iso-temperature and concentration. The Lewis number (Le) and aspect ratio are varied over a wide range to analyse non-dimensional horizontal (U) and vertical velocities (V), stream line contours, temperature and concentration gradients. The present analysis is carried out at constant Prandtl (Pr=0.7), Richardson (Ri=1.0), Darcy (Da=1.0) and Reynolds (Re=100) numbers. Results show that the fluid flow and heat transfer increase with the increase in Lewis Number and low aspect ratio. The local and average Nusselt and Sherwood numbers are also presented for the different Aspect ratio and Lewis number.

WSEAS Transactions on Heat and Mass Transfer

The numerical simulation of double-diffusive laminar mixed convection flow in a lid-driven porous cavity

In recent years, many researches are being carried out on the integration of solar thermal systems with solar photovoltaic modules in many countries for heat generation along with electricity generation. The electrical energy generated by the solar PV modules is utilized for the operation of fan. The hybrid solar photovoltaic - Thermal (PV/T) technology provides an opportunity to enhance the electrical and thermal performances. This paper deals with analysis of various parameters which affect the electrical and thermal performances of different types of hybrid solar photovoltaic - Thermal (PV/T) air heating systems. These systems deliver more useful energy per unit area of the heater than that of individual solar PV and solar thermal systems and can be used for preheating the air for many applications such as drying of agricultural products, space heating and industrial process heating. The performance comparisons among the various models reveal that the model III in which the air flows above and below the absorber plate is most suitable for converting the solar energy into high quality electrical energy and low quality heat energy.

Department of Automotive Engineering

Advanced Materials Research

A Review of Mathematical Models for Performance Analysis of Hybrid Solar Photovoltaic - Thermal (PV/T) Air Heating Systems

This study deals with the estimation of monthly average daily global solar radiation incident on a horizontal surface at a location using meteorological data for different cities of Andhra Pradesh state. The regression equations of two types of models are developed for various locations of the state having varied climatic regions using measured meteorological parameters obtained from different measuring stations. Parameters such as the latitude and height of the location, maximum and minimum temperature and relative humidity are considered to develop linear and quadratic regression equations to estimate the monthly average daily global radiation. The estimated values are compared with measured data and with other theoretical models in terms of mean percent errors calculated using recognised statistical criteria of MBE, MABE, MPE and RMSE. The proposed quadratic model performs better than the proposed linear models and shows good agreement with the long-term pyranometer data of various locations with a deviation of less than 10%. In comparison with other theoretical models presented so far, the suggested models are expected to perform with a higher degree of accuracy. © 2013 Taylor & Francis.

International Journal of Ambient Energy

New correlations for estimation of monthly average daily solar radiation on a horizontal surface using meteorological data

Solar Parabolic Trough collectors are commonly used to harness the solar power for power generating applications involving high temperatures. In the given paper study we have made use of the SolTrace software which uses the Monte Carlo algorithm for finding out the radiation received on the absorber tube of the collector. The computational study was performed taking into account the solar radiation received at Vellore city in India (12.92oN, 79.13oE) as on 16th February 2013. Further a 3D model of the absorber tube used in the parabolic trough collector was created and meshed with the help of the Ansys Gambit software. The absorber tube which we considered for our study is made up of Stainless Steel AISI 302 material. The meshed model so created was then exported to the Ansys Fluent 6.3 software and simulations were performed for different mass flow rates of the fluid. The fluid which we used in the computational analysis study is Therminol 55. The temperature differences for different mass flow rates of the liquid passing through the absorber tube were found out and based on the temperature rise contours plots so obtained, we have plotted the surface heat transfer coefficient for the absorber tube. We also found out the static temperature contour plot for the fluid flowing through the given absorber tube taking into account the heat flux acting on the absorber tube due to the hourly and daily average solar radiation.

VIT Unitversity

Applied Mechanics and Materials

Computational Study on Estimating the Surface Heat Transfer Coefficient of Absorber Tube in Solar Parabolic Trough Collector

Solar thermal energy is currently used for low temperature heating applications using flat plate collectors. The absorbed solar energy is transferred to the working fluid flowing in the pipe. The performance of the system is influenced by heat transfer from tube to working fluid, with minimum convective losses, which has to be considered as one of the primary design factor. In tube and channel flows, to enhance the rate of heat transfer to the working fluid, passive augmentation techniques such as twisted tapes and swirl generators are used in the fluid flow path. In this paper, convective heat transfer analysis for a horizontal circular pipe with fluid in mixed laminar flow range is performed using experimental simulation under constant heat flux boundary condition. The variation of heat transfer coefficient and pressure drop in the pipe flow for water and water based Al2O3 nanofluids at different volume concentrations and twisted tapes are studied. The dependence of particle concentration and Reynolds number for enhancement in heat transfer and increase in the pumping power due to pressure drop is analysed in the range of parameters considered. © 2013 The Authors. Published by Elsevier Ltd.

Fulltext

Procedia Engineering

Heat Transfer Enhancement with Al2O3 Nanofluids and Twisted Tapes in a Pipe for Solar Thermal Applications

Contemporary vehicles are required to yield superior performance with low emissions, high stability, and a high fuel economy. For the same power output, the speed of the vehicle can be increased by reducing the drag force, which is resistance to the forward motion. Under-body region of the vehicle is often neglected because of its complex geometry and the presence of uneven and cleft structures which triggers separation and turbulence. As a result the flow is decelerated and the pressure gradient becomes unfavourable which increases the pressure drag. Designing the under-body more carefully, avoiding projections and covering open areas with panels reduce the turbulence and straighten the flow, thus yielding lower drag. In the present work, numerical analysis is first made on Ahmed body flow for three different slant angles and the flow process involved in drag production is observed. Simulation results in acceptable agreement with the experimental results and thus validates this work. Later the flow around a car and the under-body region is studied using Computational Fluid Dynamic (CFD) simulation techniques. Simulations are done on a sedan type car model. The geometry was rebuilt using the blueprints and physical measurements of the road version using DASSAULT System's CATIA V5R20. The geometry was exported to ANSYS for meshing in STP format and was meshed in the ANSYS workbench module. FLUENT is used for the analysis of the meshed geometry. The simulations revealed how force, pressure distribution and velocity fields varied for different configurations with and without wheels and also by the installation of diffusers. It is observed that 30% of the drag is contributed by wheels and wheel housing. By attaching diffusers it is found that the drag values are decreasing considerably along with getting more down force. © 2013 IEEE.

2013 International Conference on Energy Efficient Technologies for Sustainability

Computational drag analysis in the under-body for a sedan type car model

Compressor is one of the main parts and it is thus the first component of the refrigerator to be modeled. Compressor would consume less work when its inlet temperature is low which is understood from the T-S diagram as the constant pressure lines diverge towards right. The density decrease due to suction gas heating and mixing is a very important factor affecting mass flow rate, and can be characterized by a single parameter, the effectiveness of heat transfer driven by the difference between the temperature at the suction line and the discharge port. The present paper is to compare theoretical and experimental values and to develop an effective suction gas heat exchanger for hermetically sealed compressor. An attempt to achieve the required temperature with in less time when compared to the refrigeration unit working without heat exchanger had been done using laboratory set up with a single tube counter flow heat exchanger. The required temperature had been achieved with in 30 minutes when compared to the refrigeration unit working without heat exchanger. Though the actual COP values are much smaller compared to than Carnot COP values, it had been proved that the values obtained with heat exchanger is 10% more than the values with out Heat exchanger.

Effect of heat exchanger influencing coefficient of performance of a hermetic compressor

Valve design is one of the most important aspects of compressor design. In designing the valve system for reciprocating compressors four main features related to the valve performance are sought: Fast response, high mass flow rate, low pressure drop when opened and good backflow blockage when closed. For this reason and in order to obtain an optimum valve system, it is crucial to recognize and predict the phenomena associated with the flow through the valve. The present research is to analyze the effective flow area across the valve section of a hermetic compressor with back flow condition experimentally. Mass flow rate has been an important parameter in analyzing the effective flow area at the valve section. Experimental set up being arranged in order to compute the mass flow rate through the valve section for various valve lifts. Using continuity equation for steady one-dimensional flow, mass flow rate through the valve section is calculated analytically. Effective flow area in terms of lift is obtained experimentally taking the design parameters like flow rate, discharge coefficient, area of cross section and static pressure across the valve section. The effective flow areas are higher at 60% of the valve lift in case of back flow conditions. These experimental results were compared with the analytical values with 5% variation, well with in the accepted limits. These results would be useful in optimizing the performance of reciprocating compressors. © Medwell Journals, 2013.