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Item Bioconversion of Glycerol by Immobilized Clostridium Pasteurianum: Process Development Optimization and Intensification(2012) Khanna, SwatiAbstract not foundItem Biodegradation of polycyclic aromatic hydrocarbons in contaminated wastewater and biodiesel production using the oleaginous bacterium Rhodococcus opacus(2019) Goswami, LalitPolycyclic aromatic hydrocarbons (PAHs) represent a unique class of ubiquitous semi-volatile organic contaminants, well-known for their persistent, bioaccumulative, toxic, carcinogenic, teratogenic and mutagenic nature. In the present study, a hydrocarbonoclastic oleaginous bacterium Rhodococcus opacus, was investigated for its potential to simultaneous degrade naphthalene, anthracene, phenanthrene and fluoranthene as model PAHs, in single, multi-component and cocontaminated heavy metal system. In single-component system containing minimal salt medium with all the four PAH compound as the sole source of carbon and energy and at an initial concentration in the range 50-500 mg L-1, R. opcaus was capable of degrading 58% - 83.8% of PAHs along with the lipid accumulation in the range 72.4% (w/w, CDW) within 7 days. In the multi-contaminated system, a maximum removal of 91.6%, 82.3% and 80.7% was achieved for naphthalene, phenanthrene and fluoranthene, respectively. The individual effect of PAH concentration was found to be more significant than 2-way and 3-way interaction effects on PAHs biodegradation. The biodegradation efficiency in the mixture was mainly affected by initial concentration and aromatic complexity of the PAHs. Furthermore, effect of six different heavy metals individually has depicted the following order on PAH biodegradation and lipid accumulation: Cd > Ni > Pb > Cu > Zn > Fe. In order to enhance PAH bioavailability by R. opacus, biochar derived cheaply from biomass gasification waste was evaluated and has shown an enhancement in PAH biodegradation in the range of 79.6% to 92.3%. The valorization of biomass gasification wastewater (BGWW) for lipids accumulation by Rhodococcus opacus was further examined.Item Bioethanol production from Parthenium Hysterophorus involving cellulase from Bacillus amyloliquefaciens SS35: : Process development, optimization and intensification(2014) Singh, ShuchiAbstract not availableItem Biohydrogen production from crude glycerol: Process optimization and intensification(2018) Sarma, ShyamaliThe proposed thesis work is aimed at optimization and intensification of a biochemical process for producing hydrogen from biodiesel–derived crude glycerol. The micro–organism used for in this study is Clostridium pasteurianum, which has a higher potential for biohydrogen production. This study aims in enriching H2 producing Clostridium pasteurianum by optimizing the physio–chemical parameters for maximal H2 production by using response surface methodology. This is followed by kinetic and thermodynamic analysis of hydrogen production for both pure and crude glycerol as substrate for fermentation. Similarly statistical optimization of the media components was also considered as one of the approach to intensify H2 production. Further to maximize valuable metabolite production, extensive analysis and understanding of metabolic pathways is required so as to redirect the cellular metabolic pathways primarily towards its production. An in silico metabolic flux model has been formulated for this analysis that determines the complete intracellular fluxes of all metabolites from experimentally measured fluxes. This methodology was used for comparative analysis of mechanical shaking and ultrasound-assisted fermentation for H2 production. The flux analysis results were further corroborated by targeting the genes involved in glycerol-hydrogen pathway of C. pasteurianum which involved overexpression of Fe-only hydrogenase encoded by hydA and the enzymes involved in glycerol metabolism encoded by dhaD and dhaK. The hydrogen production efficiency was compared between the wild type and recombinant strain of C. pasteurianum using crude glycerol as the substrate.Item Butanol Production from Rice Straw : Process Development and Optimization(2012) Ranjan, AmritaAbstract not foundItem Charging infrastructure planning for electric vehicles(2020) Deb, SanchariThe ever increasing energy demand accompanied by fossil fuel depletion and environmental degradation has paved the path of transportation electrification. Electric Vehicles (EVs) are environmental friendly alternative to conventional Internal Combustion Engine (ICE) driven vehicles. For large scale deployment of EVs sustainable charging infrastructure needs to be developed. The charging station placement problem is a complex problem involving power distribution network and road network. Charging stations must be placed in the distribution network in such a way that the negative impact of placement of charging stations on the operating parameters of the distribution network is minimized. Also, the location of charging station must be optimized considering the route behavior of EV drivers and charging demand of the EVs computed based on the driving range of the EV. Hence, motivated by all the aforementioned factors this thesis aims to delve into charging infrastructure planning for EVs. The thesis proposes single-objective, multi-objective as well as robust two-stage formulation of charging station placement problem. Moreover, hybridization of Chicken Swarm Optimization and Teaching Learning Based Optimization Algorithm (CSO TLBO) is proposed for solving the charging station placement problem. The proposed formulations of charging station placement problem are validated on superimposed 33 bus distribution and 25 node road network, city of Tianjin, and highway network of Guwahati.Item Clean Development Mechanism Potential of Compression Ignition Diesel Engines Using Gaseous Fuels in Dual Fuel Mode(2011) Sahoo, Bibhuti BhusanThe climate change problem results from the concentration of greenhouse gases (GHGs) in the atmosphere. The purpose of the Clean Development Mechanism (CDM) is to promote clean development in developing countries, and is based on the idea of emission reduction DproductionD. These reductions are DproducedD and then subtracted against a hypothetical DbaselineD of emissions. The fossil gasoline and diesel petroleum fuels used in internal combustion (IC) engines are one of the contributors to the global environmental degradation for their GHG emissions. Diesel engines contribute on important part of the worldDs transportation and industrial infrastructure, especially in heavy-duty equipment such as trucks, buses, construction and farm equipments, locomotives, ships etc. In the recent times, there are issues related to their GHG emissions such as, carbon dioxide (CO2), methane (CH4), and carbon monoxide (CO). The use of alternative fuels is one of the most effective means of resolving this problem. Gaseous fuels receive more prominence in the domain of alternative fuels because of the possibilities of cleaner combustion. However, they are not suitable for compression ignition (CI) concept diesel engine when used alone due to their low cetane numbers and high auto-ignition temperatures. Hence, the CI engine of the Ddual fuelD approach plays a significant role in the efficient utilization of a wide range of gaseous fuels. During a dual fuel operation, a carbureted air-gas mixture is sucked and compressed like in a conventional diesel engine. The compressed air-gas mixture is fired by a small liquid fuel injection, pilot, which ignites spontaneously at the end of compression process. Biogas and syngas are the two alternative gaseous fuels examined in the present investigation. In general, Biogas is produced by Danaerobic digestionD process where the timing, pilot fuel mass inducted, intake manifold conditions, and type of gaseous fuel, have effects on the performance, combustion and emission characteristics of dual fuel diesel engines. However, the systematic investigations of individual parameters relevant to engine characterization have not been reported exhaustively in the literature. The second law analysis or evaluation of available energy determines the maximum possible performance of a thermodynamic system. In addition, impact of process change in the system in terms of system losses is also assessed. These findings help in reducing the availability loss to improve the performance of the engine in terms of efficiency and power output. However, there were only few literatures accessed on availability analysis of dual fuel engines. Therefore, the present contribution is focused to perform a systematic experimental investigation including the thermodynamic behavior of diesel engine under dual fuel mode. To accomplish the above problems of diesel engines, few additional components such as gas mixer and gas carburetor were designed, developed and incorporated into the base engine setup for executing the dual fuel operation. Experiments were conducted on a modified engine test unit so as to run biogas and syngas under dual fuel operations. The base diesel engine is a single-cylinder, constant-speed, water-cooled and direct-ignition diesel engine with a rated power of 5.2 kW at 1500 rpm.....Item Cyanobacteria based photosynthetic microbial fuel cell : Development and application for sensing alcohol(2018) Kaushik, SharbaniThe major objective of the present study is to develop an efficient photosynthetic microbial fuel cell (PMFC) using cyanobacteria as anodic catalyst with a further aim of utilizing this energy generating device for sensing applications. One of the key issues to make the bacterial catalysts effective for generating power in microbial fuel cell is the proper electrical communications between the bacterial cells and the conductive electrode of the fuel cell device. We proposed the direct electron transfer (DET) as the guiding principle for channelizing the cellular electrons to the anode for which, setting up of cyanobacteria biofilm on the anode was considered as a suitable strategy to comply the principle. We explored different synthetic and natural polymeric thin films for their rapid biofilm promoting abilities of cyanobacteria, Synechococcus sp. For a comparative analysis, the study was extended to two commonly available bacteria, namely, Escherichia coli and Lactobacillus plantarum. The activating role of different polymer thin films coated over polystyrene support on the Synechococcus sp. biofilm growth was examined concurrently by measuring biofilm florescence using a dye and by measuring cell density in the isolated biofilm. Compared to blank (no coating), the increase in biofilm formation (%) on silk, chitosan, silk-chitosan (3:2) blend, polyaniline, osmium, and Nafion films were 27.73 (31.16), 21.55 (23.74), 37.21 (38.34), 5.35 (8.96), 6.70 (6.55) and (nil), respectively with corresponding cell density (%) shown in the parentheses.Item Design, installation and assessment of a novel variable compression ratio mechanism for multifuel spark ignition engine(2017) Chaudhari, Ashish JagannathThe spark ignition engines are the most versatile in the arena of internal combustion engines. Petrol fuel based spark igniton(SI) engines are designed for the cylinder bore to stroke ratio(compression ratio), spark plug location which will initiate combustion faster with faster flame speed and develops flame kernel with minimum time during combustion. As per engine manufacturers catalogue, the specified octane petrol is the best for the particular engine. In this regards, if the octane rating of the fuel changed, then the engine will not perform with the maximum efficiency. However, if there are some structural alterations are carried out as per fuel, load and speed, then the higher octane fuel can be utilized to its maximum performance. In order to achieve this objective, the novel variable compression ratio (VCR) mechanism accompanied with novel variable spark plug location (VSPL) is designed and developed which could be installed further on SI engines for online variation of VCR and VSPL. Gaseous fuels are high octane ratings and could be a good source of alternative energy source. Knowing this, the non renewable gas LPG and renewable raw biogas (52% CH4+46% CO2) are being tested in engine for VCR, VSPL and in combination with EGR. The results recommend for continuous variation of CR accompanied with VSPL as per speed, load and EGR level could certainly achieve best performance in case of both fuels.Item Design, Simulation and Experimental Investigation of High Temperature Solid-state Sensible Heat Storage Systems(2020) Vigneshwaran, KThe work on the thesis is framed to propose high-temperature thermal energy storage, mainly focusing on the design, development and performance investigation of solid SHS. A high-temperature test facility has been built to study the performance characteristics of the TES modules. In the initial phase of research, the study focused on detailed experimental and numerical investigations on a cast steel based sensible heat thermal energy storage system using air as a heat transfer fluid. A dedicated test facility has been designed and developed for studying the performance of the storage system operating in the temperature range of 393 K to 573 K. Three-dimensional (3-D) and one-dimensional (1-D) models are developed for predicting the heat transfer characteristics of the storage system. The developed storage prototype has a shell and tube configuration having 19 passages in the tube side for heat transfer fluid flow. The performance of the storage system during the charging and discharging processes is analysed by varying the operating temperature range and flow velocity of air. The heat transfer characteristics of the system in terms of axial and radial temperature variations are recorded and analysed. Both the experimental and 3-D simulation results show a significant temperature variation in the axial direction than radial direction. The charging and discharging rates are found to be faster at a higher flow velocity of air. The predictions from both 3-D and 1-D models are consistent with the experimental data. The validated 1-D model can be used for real-time monitoring, control, optimisation and integration with various storage applications. In the next phase of research, the work presents the concept of developing a cost-effective Concrete based Thermal Energy Storage (CTES) system by performing extensive experimental studies and numerical simulations. A stand-alone experiment facility to study the performance of high-temperature thermal energy storage system, which operates up to 773 K using air as the heat transfer fluid, has been developed. The CTES module is made of shell and tube configuration, where the concrete is filled in the shell side, and 22 air passages are provided on the tube side. The inlet air temperature and velocity are the decision parameters used for analyzing the thermal behaviour of the CTES module. From the spatial variations of temperature, it is observed that the heat transfer rate is uniform and faster along all radial planes, whereas, the heat transfer rate drops gradually along the length of the CTES module due to drop in Heat Transfer Fluid (HTF) temperature. The parametric investigation conducted shows that the charging and discharging times were reduced by approximately 48% and 29%, respectively, with a change in inlet temperature of 40 K and at a fixed air velocity of 2 m/s. A 3-D model for the CTES module developed using the finite element method has been validated with experimental results. The temperature contours plotted from 3-D simulation describes the spatial variation of CTES temperature at different inlet air temperatures. Further, a 1-D dynamic model has been developed, which is fast and accurate with a maximum error of ±4.9 K with reference to real-time experiments and provides a substantial scope of integrating the CTES with industrial applications. In the final phase of research, a comprehensive coupling strategy is developed to evaluate the performance of a multi-module SHS system using the 1-D dynamic model. The validated 1-D model developed in our previous studies are adopted to scale-up the heat storage capacity for large scale application. The SHS modules used in this study are made of materials such as cast steel, cast iron and concrete with the design similar to shell and tube configuration. Air is used as the heat transfer fluid at a velocity of 15.2 m/s. Six Cases are framed to evaluate the charging (493-573 K) and discharging (373-573 K) behaviour of SHS module coupling strategies in different series and/or parallel arrangements. The performance of the charging and the discharging processes for all the Cases are estimated and compared for forward flow and reverse flow patterns and reverse module arrangements. The cost of the net energy discharged (USD/kW-h) from each arrangement is evaluated. The result shows that the performance of Case 6 (three parallel channels, with two different SHS modules in each channel) is better in terms of heat transfer rate and however, the cost of net energy discharged in Case 6 is 62.26 USD/kW-h, which is very expensive. The Case 3 (six concrete in the series arrangement) can store and discharge more amount of heat with slow heat transfer rate, and the cost of net energy discharged in this Case is 1.18 USD/kW-h. The developed flowsheet models are highly beneficial for studying the performance of the different storage module arrangements along with large scale applications. The outcomes from the studies highlight that cast steel and concrete TES storage modules are the cost-effective and viable high-temperature storage option for multiple thermal cycles with excellent durability.Item Development and performance evaluation of a natural convection grain dryer .2012.(2012) Mohapatra, Siba ShankarAbstract not foundItem Development of alternative dielectric fluid for power and distribution transformer(2019) Maharana, MrutyunjayThe thesis presents development of alternative dielectric fluid for power and distribution transformer. It addresses the nanofluid (NF) development and modification in the transformer oil (TO). It also addresses the development of vegetable oil (VO) based TO is a potential insulating liquid dielectric for the transformer. In the present study deals with the development of stable mineral oil (MO) based nanofluid (NF) for transformer application. Due to an extraordinary thermal and insulating properties of the hexagonal boron nitride (h-BN) nanoparticle (NP), it is selected as a material to be dispersed in MO to prepare the NF. Bulk h-BN NP of size 1 μm is exfoliated into 2-D nanosheets of size 150-200 nm subsequently enhancing the surface area of exfoliated h-BN (Eh-BN).An open beaker, single temperature oxidative thermal ageing experiment is performed at 115oC for different ageing times, i.e. 164, 328, 492 hours. A concentration of 0.01wt% of NP for both titanium oxide (TiO2) and Eh-BN/MO are selected to prepare the NFs for ageing. The superiority in physicochemical and insulation performance of Eh-BN/MO-NF are observed compared to TiO2 NF and MO at post ageing condition.Item Development of an efficient photovoltaic thermal collector(2020) Das, DudulDue to the rise in greenhouse gas in earth atmosphere and global climate change, attention has been focused on harvesting energy from renewable resources such as solar, wind, hydro, biomass, geothermal tidal, wave, and ocean thermal energy. The global potential of solar energy is higher than the potential of all other renewable energy sources together. Solar energy is primarily harvested using two prominent conversion methods viz. solar thermal and solar photovoltaic (PV). In practice, solar PV conversion is quite common for power generation due to its inbuilt advantages like no moving parts, easy installation, availability of raw material and life of operation. However, PV system suffers from its lower conversion efficiency as well as a decrease in efficiency with the rise in cell temperature. PV cell converts only a small fraction (less than 20%) of irradiance into electrical energy. Infra-red radiation absorbed by the PV reduces the electrical efficiency of the cell. The influence of temperature on the electrical output is significant at higher cell temperature (>42 °C). To address this difficulty, solar photovoltaic-thermal (PV/T) collectors are proposed. PV/T is a promising technology where both electrical and thermal energy generation can be possible. Cooling uniformity and efficiency of the PV/T system are major challenges for its applicability. The present study is formulated to address the current challenges associated with the existing PV/T collectors. A novel thermal model of a PV/T system (tube and sheet type collector) by considering thermal contact resistance between the layers of a PV/T system, individual resistance of each layer and Ohmic heat generation in the PV layer has been carried out. The Root Mean Square Errors (RMSE) of 3.75 K, 1.36 K and 2.71 K were found for the water outlet temperature, glass surface temperature and cell temperature, respectively. The results illustrated that consideration of thermal contact resistance and Ohmic loss at the PV layer increases the accuracy of the model significantly. Based on the numerical investigation, initially two PV/T collectors viz. only tube absorber (M1) and sheet-tube (M2) configurations were developed. The cells in the PV/T collectors are made of Si-multicrystalline. Both the collectors have vertical oscillating tube assembly pattern. The performance of collectors are extensively studied under outdoor conditions. Higher thermal efficiency has been reported for the collector without absorber sheet. This is due to less resistance to the thermal energy transfer from the top surface of the PV/T collector to the flowing fluid in the tubes as compared to the module with sheet-tube configuration. Two more PV/T collectors namely rectangular spiral (M3) and horizontal oscillating (M4) transparent PV/T collectors without absorber sheet were developed and a comparative experimental investigation has been carried out. The performance of the M3 collector is found to be superior and hence considered for further investigation. Finally, a form-stable phase change biocomposite has been developed using water hyacinth biochar as matrix. The developed material is applied in the M3 collector for investigation of cooling uniformity. The results of the experiments demonstrate that the use of PCM- biocomposite improves the cooling uniformity, which further results in the enhancement of electrical output by 18.4%. Furthermore, this arrangement improves the thermal efficiency by 15.7% as compared to the M3 without the PCM- biocomposite. Based on the study M3 collector with PCM-biocomposite is found to be the best amongst all the developed collectors in terms of cooling uniformity, performance and cost.Item Development of Nanocomposite Based Bioelectrodes using Alcohol Oxidase and Laccase as Biocatalysts for Bioelectronic Applications(2015) Das, MadhuriThis study at fabricating alcohol oxidase( based bioelectrode for biosensors and biofuel cell application...Item Dilute acid and ionic liquid based pretreatment of lignocellulosic biomass towards fermentable sugars(2017) Dash, MadhusmitaThe current study focuses on physico-chemical characterization and pretreatment of three commonly available lignocellulosic biomasses of North-East India such as Castor (Ricinus communis), Jatropha (Jatropha curcas), and Miscanthus (Miscanthus Sinensis) for second generation biofuels production. It was found that the cellulose content of three biomasses varied from 40% to 44%, hemicellulose content from 8% to 14% and lignin content varied from 21% to 30%. Chemical structure of lignocellulose is studied through FTIR. The crystallinity index of Castor and Jatropha was similar, i.e., 69%, whereas crystallinity index of Miscanthus was 72%. Due to the presence of higher carbon and cellulose content along with less moisture (10%–12%), ash (5%–10%), sulphur (0.1%– 0.8%), and extractives (12%–20%) makes them very good feedstock for the production of alcoholic fuels through biochemical route. Thermogravimetric analysis of these three lignocellulosic biomass under high purity nitrogen atmosphere were carried out over a temperature range of 25 oC–900 oC at three different heating rates of 10, 15, 20 oC min–1. The activation energy and pre-exponential factors were calculated by applying two modelfree methods and compared. The kinetic parameters obtained from Kissinger and Ozawa methods were in good agreement with the experimental results. The value of kinetic parameters explained the thermal stability of the biomass. The thermal analysis could not infer the composition and chemical structure of lignocellulosic biomass; hence FTIR spectroscopic analysis has been carried out.Item Experimental investigation of lignocellulosic biomass for biogas production(2019) Yadav, DiptiIntensifying environmental issues, the rising demand for energy, political apprehensions and the medium-way depletion of fossil fuels has generated the prerequisite for development of sustainable technologies based on renewable economic resources. Biogas is one of the potential alternatives biofuels identified so far and is economically feasible, which might be benefit to meet the future energy supply demands as well as contributing to a reduction of greenhouse gas emissions. Traditionally, livestock dung has been utilized as feedstock for biogas production but due to unavailability, imbalances and failure occurs in large scale biogas plants, lignocellulosic biomass has attained huge attention. Lignocellulosic biomass acknowledged as the most abundant low cost resources for renewable energy generation across the globe. The socio-economic implication is also very prodigious. Energy crops, saw dust, marine weeds, agricultural residues or waste vegetables and woody plants fall under this category. The benefit of using this class of biomass does not compete with the arable land. In the Organisation for Economic Co-operation and Development (OECD) countries lignocellulosic biomass disposed of openly, which origins environmental pollutions as well as root cause for many diseases. Although the complex structure of lignocellulosic biomass is a challenge for its utilization as feedstock in anaerobic digestion system.Item Germplasm Evaluation, Environmental Impact Assessment and Genetic Improvement Studies in Jatropha curcas(2012) Mazumdar, PurabiThe utilization of plant biofuel based Jatropha curcas feedstock is emerging as promising solution to problems of depletion of fossil fuel, fuel crisis and concern over global climate change. Large scale profitable cultivation of Jatropha is still in its infancy due to low and inconsistent yield and slow progress in identification of elite germplasm. Identification of elite germplasm from diverse agro-climatic region vis-a-vis development of superior genotype for higher seed yield and oil content, earlier maturity, reduced plant height, resistance to pests and diseases, drought resistance/tolerance, higher ratio of female to male flowers and improved fuel properties is expected to enhance the utility of Jatropha seed feedstock for biofuel. Adaptation of Jatropha to a wide range of climatic conditions including Northeast India, one of the biodiversity hot spot of the world, suggests existence of considerable genetic variation in growth and seed oil traits which can be potentially harnessed for selection of elite germplasm having high oil content and yield. Systematic analysis of the seed oil content and physicochemical properties forms the basis for identification of elite lines of J. curcas for commercial biodiesel production program. Life cycle assessment of Jatropha based biodiesel production can indicate its environmental impact and this analysis can also assist in adapting to appropriate biodiesel feedstock with minimum impact on environment. Lack of disease and stress tolerant accessions of Jatropha prohibits its successful commercial plantation program. Introduction and expresssion of crystalline toxin genes (cry) derived from Bacillus thuringiensis (Bt) through transgenic approaches have proven as effective mechanisms for protecting crops against insect infestations. In Jatropha, absence of an efficient and reproducible in vitro regeneration system amenable to gene transfer through Agrobacterium-mediated transformation hinders its genetic improvement program. In the present study, elite accessions of J. curcas from Assam, a state in North East India were identified on the basis of their seed trait and oil content. The oil content of the four elite accessions was found in the range of 37.6-46.6%. Analysis of physico-chemical properties of the oil and biodiesel obtained from seeds of these elite accessions demonstrated that they were within acceptable range of standards specifications of ASTM D6751. Life cycle assessment of Jatropha biodiesel production indicated its cultivation process generating highest environmental impact as compared to other stages of its life cycle, and showed higher sustainability of biodiesel from Jatropha as compared to Pongamia. An efficient and reproducible de novo plant regeneration system from cotyledonary leaf segment explants amenable to genetic manipulation through Agrobacterium-mediated transformation was established. The choice of explants of appropriate age and the orientation of the explants in culture medium were found to exert significant influence on the frequency of de novo plant regeneration. Furthermore, the age of the explant was found to be the critical aspect in conferring appropriate biological condition of the explant vital for optimal infection and T-DNA transfer by Agrobacterium tumefaciens. Highest regeneration response was reported.Item Growth and study of optoelectronic properties of a-Si:H/nc-Si:H based superlattice structures(2018) Yadav, AshaMultilayer/superlattice structures of a-Si:H/nc-Si:H, show many interesting features such as enhanced carrier mobility and enhance photosensitivity etc. Superlattice structures based on amorphous layer have also been proposed as a novel transistor. Though a-Si:H/nc-Si:H superlattice structures show many interesting properties, the main challenge in superlattice structures based electronic devices is the interface states. These interface states between the sublayers act as recombination centers thereby controlling the transport mechanism and overall performanance of the devices. In the present thesis, the influence of these interface states on electrical transport in a-Si:H/nc-Si:H multilayer structures has been studied using persistent photoconductivity (PPC) and SCLC measurements. No PPC was observed for the single layer films whereas, incase of multilayer films a significant amount of PPC(%) has been observed with higher DOS as compared to single layers films. Such superlattice structures also helped in the growth of controlled size Si nanocrystals in amorphous matrix, resulting in visible photoluminescence at room temperature without any post deposition processing. Nanocrystalline-amorphous Si superlattice offer a unique pathway for synthesizing embedded Si nanocrystals with controlled size and photonic signatures.Item Investigation of Hydrodynamics and heat Transfer Characteristics with Biomass Blends in a Pressurized Circulating Fluidized Bed(2013) Kalita, PankajPressurized circulating fluidized bed (PCFB) is gaining popularity among the scientific community in utilizing low grade fuel for the combustion and gasification applications due to its in-built capability of capturing of sulphur and NOx. Compactness, high heat release rate and less amount of sorbent requirement makes the PCFB system more attractive. However, the complexity in hydrodynamics and heat transfer phenomena associated with bed geometry, flow parameters as well as type of fuels etc., demands for extensive research so as to open an avenue for designing of a PCFB system. In the present investigation, two PCFB units (one cold bed and the other being hot bed) of similar dimensions have been designed and fabricated in order to investigate the hydrodynamics and heat transfer characteristics experimentally. The bed hydrodynamics along the height of the riser was investigated in the cold bed unit. The effect of superficial velocity, solid inventory, particle size and operating pressures were investigated on bed voidage and suspension density. A heat transfer probe was installed at the upper splash region of the riser to investigate the wall-to-bed heat transfer coefficient along the height of the probe. The radial variation of heat transfer coefficient was investigated at a height of 1.57 m from the distributor. The hydrodynamics and heat transfer characteristics for different blending ratios of sawdust with sand and different weight composition ratios were also investigated at different operating conditions. The hot PCFB unit has been developed to investigate the effect of temperature and pressure on bed-to-wall heat transfer and quality of product gas at different biomass blending ratios. Gas composition was evaluated with the help of a gas chromatography and a flue gas analyser. Two heat transfer probes were installed at the upper splash region of the riser to investigate the heat transfer coefficient. The heat transfer coefficient was calculated without and with twisted tapes at different solid inventories and the performance was compared. Results obtained in the present investigation were found to be well comparable with the published results. The blending of biomass used for the above investigation in the PCFB units has been characterized to understand the change of thermal property with the increase of rate of heating. To investigate the effect of heating rates on the degradation of biomass the experiments were performed at three different heating rates of 10, 30 and 80 ओC/min while performing thermogravimetric (TG) analysis. The degradation of mass with temperature was validated numerically. The kinetic parameters of biomass were evaluated for both first and second reaction zones. The thermal response of biomass undergoing decomposition has also been modelled by using one dimensional (1-D) transient thermal model. The model was tested by using transient conduction Heisler chart. This study is important to understand the requirement of optimum fluidizing air for a combustor and to maintain a temperature required for gasification when it operates below sub stoichiometric condition.Item INVESTIGATIONS ON USABILITY OF POROUS MEDIA IN KEROSENE PRESSURE STOVES FOR IMPROVEMENT OF THERMAL PERFORMANCE(2010) Sharma, MonikankanaIn developing countries, kerosene is considered as one of the principal cooking fuels and it is normally burnt in two kinds of stoves: wick type and pressure type. The pressure type stoves perform reasonably well; however the growing awareness about conservation of energy and reduction of pollution has necessitated their further improvements. Towards the above goal, in this study, a conventional kerosene pressure stove was modified to incorporate a bi-layered porous media consisting of alumina (Al2O3) and silicon carbide (SiC) enclosed in 6 different types of casing in the combustion zone. The thermal performance of the stove was evaluated with each type of casing. The main aspects of the thermal performance include temperature, emission and efficiency measurements. The emission and efficiency studies were conducted for different fuel and air flow rates. It was observed that the burner could be operated in a much leaner condition without affecting the stability of the flame. CO and NOx were measured at different air fuel ratios. The lowest CO emission (30 ppm) was observed for the fuel flow rate: 220 g/hr and air flow rate 120 lpm. CO emission was found sensitive to heat input and air flow rate. While, NOx behaviour was found insensitive to both heat input and air flow rate. The lowest NOx recorded was 1.2 ppm. The temperature measurements were taken at different radial and axial locations. The average surface temperature was found ~800 oC and it was found to increase with increase in air and fuel flow rates. The efficiency test of the burner was conducted as per the standard water boiling test (WBT) in accordance with the BIS standard: IS 10109: 2002. The highest efficiency (~57%) was recorded for the fuel flow rate: 160 g/hr and air flow rate rate: 150 lpm and this was obtained for a conical casing. Further, the efficiency also varied with vessel sizes and the different spacings between the vessel and the burner.The optimum distances giving the best thermal performance have been identified. An analysis has been carried out to calculate the efficiencies of the burner,working in different operating conditions, from the second law point of view. It was found that with increase in air flow rate the energy efficiency or the first law efficiency increases, while the exergy efficiency decreases. Similarly, the exergy efficiency increases with increase in fuel flow rate which is reverse in case of the first the efficiency. Thus, considering both first law and second law efficiencies, the air flow rate 120-130 lpm was found optimum. The conical casing shows the highest second law efficiency too. Finally, the thermal performances of the stove with new burner were compared with a conventional BIS specified stove. For the same heat input, the conventional stove showed higher CO (80-90 ppm) and NOx (3-4 ppm) but first (thermal efficiency) and second law efficiencies (exergy efficiency) were comparable.....