@article { ISI:000246157400009, title = {Effect of sparger design on the flow in a bubble column: symbolic analysis of LDA data}, journal = {Industrial \& Engineering Chemistry Research}, volume = {46}, number = {10}, year = {2007}, month = {MAY}, pages = {2996-3007}, publisher = {AMER CHEMICAL SOC}, type = {Article}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

This paper aims at developing a methodology that helps in the characterization of the effects of a single point and multipoint sparger on the flow patterns in a bubble column reactor. The methodology uses the simultaneously measured instantaneous velocity-time data (two orthogonal velocity components) using LDA at different measurement locations. The data sets are transformed into their equivalent description in terms of polar coordinates, viz., resultant velocity vector and angle. This information is further transformed in terms of symbolic representation in a binary number format. The covariance matrices obtained from the binary data are analyzed for their eigenvalues, and the spectrum is used for the identification of the dominant, energy containing modes in the data. In the vicinity of the sparger, the nature of covariance matrix and the eigenvalue spectrum for the single point sparger (SPS) data was significantly different from that of the multipoint sparger (MPS). In the bulk region, for both types of spargers, the nature of the eigenvalues and the number of dominant modes is seen to be different from the near sparger region. In general, more numbers of eigenvalues are required to capture the total energy in the data for a multipoint sparger when compared to a single point sparger. This suggests a higher level of complexities existing due to the intricate hydrodynamics for the multipoint sparger. The possible use of this methodology for practical purposes, e.g., identification of malfunctioning of gas-liquid sparger reactors is discussed.

}, issn = {0888-5885}, doi = {10.1021/ie060778e}, author = {Kulkarni, A. A. and Deshpande, Suvarna S. and Joshi, J. B. and Kumar, V. Ravi and Kulkarni, B. D.} } @article { ISI:000271103500012, title = {Effect of flow structures on heat transfer in single and multiphase jet reactors}, journal = {Industrial \& Engineering Chemistry Research}, volume = {48}, number = {21}, year = {2009}, month = {NOV}, pages = {9428-9440}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

High frequency experimental measurements by hot film anemometry (HFA) of liquid velocities and temperature in the region of vapor-liquid (VL) and solid-liquid (SL) interfaces for two important reactor types, namely, condensation jet and jet loop reactors, have been studied for their heat transfer characteristics. An algorithm for flow structure identification has been devised from velocity data based oil (i) zero crossings and (ii) continuous wavelet transform. The wavelet transform algorithm is especially found to be useful in accurately estimating both the age and size distributions of eddies near interfaces in a multiscale framework Using these distributions, it is shown that the calculated values of heat transfer coefficients (HTC) at the SL and VL interfaces show remarkable correspondence with the HTC values obtained experimentally from instantaneous temperature measurements. For this purpose, a modified capacitance model has been proposed that takes into account the information about both the age and size distributions. The results obtained by the present methodology show the improvement possible for calculating the HTC at interfaces when compared with the earlier surface renewal models. It may therefore be used to study the interaction between flow dynamics and heat transfer behavior in chemical process equipment

}, issn = {0888-5885}, doi = {10.1021/ie900052s}, author = {Deshpande, Sagar S. and Mathpati, Channamallikarjun S. and Gulawani, Sagar S. and Joshi, Jyeshtharaj B. and Kumar, V. Ravi} } @article {45940, title = {Embedded multiple shooting methodology in a genetic algorithm framework for parameter estimation and state identification of complex systems}, journal = {Chemical Engineering Science}, volume = {134}, year = {2015}, month = {SEP }, pages = {605-618}, type = {Article}, abstract = {

A novel parameter estimation and state identification algorithm for nonlinear dynamical systems from data by embedding a multiple shooting methodology in the framework of a genetic algorithm (EMSGA) is described. The advantages of EMSGA are brought out by studies with two highly nonlinear examples, viz., the chaotic dynamics of a non-isothermal CSTR and the glycolysis regulation in Lactococcus lactis for production of lactic acid. For the chaotic dynamics with extremely high sensitivity to parameter values and initial conditions, EMSGA accurately estimates all process parameters while at the same time recovering the true dynamics of monitored and unmonitored variables from limited extents of noisy dynamic data. The superiority in accuracy and computational time of EMSGA over standalone genetic or multiple shooting algorithms for parameter estimation is shown for comparison purposes. In fact, EMSGA adapts well to the use of generalized canonical models, e.g., the S-system, where use of the fundamental Taylor series method of any order for integration becomes possible. This makes EMSGA highly efficient and exemplified here by estimating all the parameters of the derived higher dimensional 5-system model for the CSTR. Comparative studies with a well-known global-local enhanced scatter search method corroborate the suitability and advantages of the EMSGA methodology. For the glycolysis regulation example the numerical robustness of EMSGA is brought out by estimating a large number of model parameters when a majority of them are raised to the power of the state variables. Interestingly, we show that from noisy in vivo dynamic data it becomes possible to completely recover the noise-free dynamical behavior of unmonitored species concentrations using EMSGA. (C) 2015 Elsevier Ltd. All rights reserved.

}, keywords = {Canonical models, Chaotic dynamics, Genetic algorithm, Multiple shooting, Noise reduction, parameter estimation}, issn = {0009-2509}, doi = {10.1016/j.ces.2015.05.040}, author = {Sarode, Ketan Dinkar and Kumar, V. Ravi and Kulkarni, B. D.} } @article {44471, title = {Evaluation of Candida tropicalis (NCIM 3321) extracellular phytase having plant growth promoting potential and process development}, journal = {Biocatalysis and Agricultural Biotechnology}, volume = {13}, year = {2018}, month = {JAN}, abstract = {

Phytase is known to provide a solution for depletion of phosphorus (P). It helps it by hydrolyzing the insoluble P source in soil which is phytate. In this study, provides insight on yeast Candida tropicalis (NCIM 3321) which produces cell bound and extracellular thermostable phytase. The media components were optimized to enhance the enzyme production and checked for plant growth promoting activity. On optimization the isolate exhibited enhanced cell bound and extracellular phytase activity by four folds (from 236 to 1024 IU DCG$^{-}${\textonesuperior}) and by five folds (from 0.46 to 1.95 IU ml$^{-}${\textonesuperior}) respectively in 36 h. The production time decreased to 24 h compare to shake flask on Up-scaling the production process upto 10 L scale, thus increasing the productivity of cell bound (1810 IU DCG$^{-}${\textonesuperior}day$^{-}${\textonesuperior}) and extracellular phytase (6.08 IU ml$^{-}${\textonesuperior} day$^{-}${\textonesuperior}). The crude phytase (12 IU) from NCIM 3321 strain was studied for plant growth promotion activity in lab scale and field level experiments with maize crop. Findings of the study revealed that the extracellular phytase derived from non pathogenic C. tropicalis (NCIM 3321) was found to be plant growth stimulating by increasing the available P in soil. Our findings of phytase isolated from non-pathogenic yeast C. tropicalis NCIM 3321 exhibited dephytinization potential. Therefore, current study may have profound application in sustainable agriculture.

}, doi = {10.1016/j.bcab.2017.12.013}, author = {Puppala, Kumar Raja and Naik, Tejali and Shaik, Alfina and Dastager, Syed and Kumar, V. Ravi and Khire, Jayant and Dharne, Mahesh} }