42 research outputs found
Mixing and regime transition analysis of liquid-solid conical fluidized bed through RPT technique
No full textThe current work focuses on the hydrodynamic study of liquid-solid mono and binary conical fluidized bed using the radioactive particle tracking technique. Two different sizes 0.6 and 1 mm diameter glass beads were used for the experiment. Two different bed compositions, mono dispersed (100 wt% of each solid) and 50 wt% mixture of the solids, were studied. A rich data base, including instantaneous velocities, mean and RMS velocities, granular temperature, etc., were calculated by suitable post-processing. Further, Hurst exponent, autocorrelation function, segregation index, Kolmogorov entropy, and correlation dimension were calculated using time series data to understand the mixing and chaotic nature of the fluidized bed for each set of data. Good degree of mixing was observed even at a low velocity of 0.07 m/s. Kolmogorov entropy and correlation dimension indicate regime change at liquid inlet velocity of 0.1 m/s for both mono and 50 wt% binary bed.Fil: Kalo, Lipika. Indian Institute of Technology Guwahati; IndiaFil: Kamalanathan, Premkumar. Bhabha Atomic Research Centre; IndiaFil: Pant, Harish J.. Bhabha Atomic Research Centre; IndiaFil: Cassanello Fernandez, Miryam Celeste. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias. Instituto de Tecnología de Alimentos y Procesos Químicos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Tecnología de Alimentos y Procesos Químicos; ArgentinaFil: Upadhyay, Rajesh K.. Indian Institute of Technology Guwahati; Indi
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No full textVirtual tracer response methodology developed based on the trajectory data of the computer aided radioactive particle tracking (CARPT) technique was demonstrated. The demonstrated virtual tracer technique has advantages of non-invasiveness, near perfect injection/sampling, and flexibility in choosing the sampling/injection boundaries in a specific spatial pattern. With the developed virtual tracer technique, liquid and solids backmixing were investigated at the conditions mimicking Fischer-Tropsch synthesis. Experiments were conducted at different pressure, solids loading, and superficial gas velocity. The axial dispersion model (ADM) and recirculation and cross flow dispersion (RCFD) models were used to model the liquid mixing. Transient sedimentation dispersion model (SDM) was used to model the solids mixing. It was found that the measured axial dispersion coefficient (Dl) in the ADM model increases with increase in the pressure. The increase of dispersion coefficient was explained with the experimental values of mean axial diffusivity and mean recirculation velocity. Axial dispersion coefficients (Dz,uDz,d) in the RCFD model (compartment model) were apparently lower than the Dl, due to the decoupling of global recirculation from the dispersion coefficients in the RCFD. Further, it was found that the dispersion coefficients in the RCFD model follow the trend of the axial eddy diffusivity with change in the operating conditions revealing the dominance of the turbulence in the upflow and downflow compartments. From the solids backmixing study, axial dispersion coefficient (Ds) of solids was found to increase with increase in the solids loading, pressure, and superficial gas velocity at the studied conditions
Gas-Liquid Mass Transfer using Advanced Optical Probe in a Mimicked FT Slurry Bubble Column
No full textGas-liquid volumetric liquid-phase mass transfer coefficient (kLα) was studied in a slurry bubble column at the conditions mimicking Fischer-Tropsch synthesis. To avoid the hydrodynamic disturbances due to the gas switching, oxygen enriched air dynamic absorption method was used. Influence of reactor models (CSTR, ADM and RCFD) on the volumetric mass transfer coefficient was investigated. Effect of operating pressure, superficial gas velocity and solids loading were investigated. From the reactor models investigated, it is recommended to use ADM model for kLα study. If the CSTR model is used, applicability of the model should be checked. With increase in the superficial gas velocity and operating pressure, volumetric liquid-phase mass transfer coefficient increases, while it decreases with the solids loading corroborating with the literature
Voltage Regulation on High PV penetrated Distribution system using Electric Vehicles
No full textThe penetration of renewable energy sources is increasing every year and that poses a lot of challenges in the distribution system. Since they are intermittent in nature, they cannot serve the energy demand as stand alone sources without the help of storage technologies or stable energy sources. As the RES, especially the Photo Voltaic generation units are often connected in the distribution system, their intermittent nature may result in a sudden rise or fall in overall generation. Hence the voltage has to be kept within limits to prevent the failure of the system. Storage technologies plays an important role in keeping the voltage levels under control. From the consumer perspective, the usage of electric vehicles is steadily increasing and most of the vehicles are connected to public charging stations to charge the vehicle battery. Hence there is an interaction between the EVs and distribution grids, which is utilized as a storage option here. In this research, the voltage changes due to the penetration of renewable energy sources in the distribution system is regulated by using the electric vehicles as a storage option. This thesis tries to give an understanding on the strategy applied towards regulation of voltage in the distribution system using electric vehicles. The strategy will serve as a platform for regulating voltage using electric vehicles and it can be adapted to any such distribution network. This strategy takes into account the size and capacity of the battery, battery state of charge and the availability of electric vehicles for a given day. Consensus algorithm serves as the communication platform for information interchange between the electric vehicles connected in the network. Average consensus algorithm estimates the average state of charge of the electric vehicles connected in the distributed network and that has been used to ensure equitable contribution of power among the electric vehicles. Markov model is used to simulate the travel pattern of the electric vehicles. This provides a more realistic and accurate pattern of travel. Markov model is implemented with and without considering time of occurrence and the results shows that the pattern is more accurate when time is considered as a parameter. Considering the generated travel pattern, voltage level of the buses in the network and the output from the consensus algorithm, the voltage has been regulated. The Electric vehicles are used for regulating the voltage when the voltage level is beyond the tolerance limits, and during other times, the electric vehicles charge their batteries. This is executed by controlling the charging and discharging cycles of the electric vehicles. The results are discussed based on different cases and the advantages and limitations of each case is explained in detail. The simulation is not robust since the availability of electric vehicles is uncertain. To make it more robust, monte carlo simulations are used. The probability of occurrence of several events has been estimated using monte carlo simulations and through the results, the availability is predicted to a certain extent. Different cases are implemented and analysed and the results shows that the availability depends on the bus, the location of the bus and the travel behaviour of the electric vehicles. Each case is discussed separately and the degree of uncertainty is reduced at the end.Electrical Engineering | Sustainable Energy Technolog
Study of the Detailed Catalyst Hydrodynamics using Radioactive Particle Tracking Technique in a Mimicked Fischer-Tropsch Slurry Bubble Column
No full textSlurry bubble column reactor (SBCR) is the preferred choice of reactor for Fischer – Tropsch (FT) synthesis. However, the understanding of the catalyst flow dynamics in FT-SBCR is still lacking. In this work, hydrodynamics of the FT catalyst were studied using computer aided radioactive particle tracking (CARPT) technique at the mimicked conditions of FT synthesis for the first time. Solids ensemble averaged velocity, turbulent kinetic energy, Reynolds normal and shear stresses were experimentally obtained. Effect of operating conditions on the velocity flow field were investigated. Further, studies were conducted to quantify the difference in flow field due to the change in the liquid and solid phases. It was found that the change of solids turbulence is insignificant with pressure and solids loading at the studied operating conditions. Further, it was found that the surface tension of the fluid and the solid properties plays a dominant role on the turbulence
Integration of Phase Distribution from Gamma-Ray Tomography Technique with Monolith Reactor Scale Modeling
No full textIn this work, a monolith reactor model was developed to study the effect of phase distribution on the performance of the monolith reactors by integrating phase distribution data from the experiments. To obtain the phase distribution at the reactions conditions, gamma ray computed tomography (CT) was used. Effect of gas density, surface tension of liquid and operating conditions on the phase distribution were studied using gamma-ray computed tomography. Experiments were conducted in Taylor flow regime. With the increase in gas density, uniformity increases. Surface tension has little effect on the distribution in the investigated conditions. Liquid with lower surface tension and gas with lower density has higher cross-sectional liquid saturation. Further, the monolith reactor model with uniform phase distribution and actual distribution were compared. It was found that at higher velocities both gives the same reactor performance irrespective of the maldistribution, however at low velocities, they differ significantly due to the maldistribution. If the maldistribution is present at both low and high velocities, catalyst utilization plays a major role, thus it is recommended to operate at higher velocities where catalyst utilization is high due to high mass transfer
Effect of dynamic bias on accuracy of radioactive particle tracking (RPT) technique at different data acquisition frequencies
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New Initiative: The Naturalness of Software
No full textAbstract—This paper describes a new research consortium, studying the Naturalness of Software. This initiative is supported by a pair of grants by the US National Science Foundation, totaling 600,000 helped kickstart an inter-disciplinary effort, and demonstrate feasibility; a follow-on full grant of $2,000,000 was recently awarded. The initiative is led by the author, who is at UC Davis, and includes investigators from Iowa State University and Carnegie-Mellon University (Language Technologies Institute). I
