Kameswara Upadrashta
Process Research, Analysis & D...

Engineering

PhD Chem Engng
2.86

Publications

  • K.R. Upadrashta, D. Venkateswarlu, J.D. Miller
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    ABSTRACT: A semitheoretical correlation for classification size applicable to pulps in which the continuous phase is a power-law fluid is derived based on the concept of equilibrium orbits. The effects of turbulence and volume fraction of solids are considered. The d50 values predicted by the correlation are compared with actual test values and with those predicted by earlier correlations appropriately corrected for fluid apparent viscosity. Two well known models for grade efficiency curve are evaluated in the light of original test data on concentrated pulps involving power-law fluids. The relationship of the actual d50 with the solids recovery in the underflow, and the distribution of solids and fluid in the underflow and overflow streams, are sudied.
    13th Annual Powder & Bulk Solids Conference (organized by Powder Advisory Centre, London); 05/1988
  • K.R. Upadrashta, K.D. Lund
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    ABSTRACT: Five two-parameter models for separation curves of dense-media cleaning of fine coals have been evaluated in the light of new pilot plant test data on a 250 mm cyclone. The two parameters involved in each of the models are: *an index of the sharpness of separation and *the relative density of separation. One of the models has been selected on the basis of its adequacy, flexibility, and simplicity. Then the sharpness-of-separation index has been subjected to multivariable regression in terms of four major design and operational parameters of the cyclone. A quadratic expression incorporating the interaction terms has been obtained and reduced to canonic form. Canonic axes have been determined and response surfaces plotted which represent the effect of simultaneous variation of any two variables on the sharpness index. Lastly, the relationship of the relative density of separation with the mass recovery in cyclone underflow is discussed.
    13th Annual Powder & Bulk Solids Conference (organized by Powder Advisory Centre, London); 05/1988
  • K.R. Upadrashta, V.J. Ketcham, J.D. Miller
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    ABSTRACT: The tangential velocity profile for pseudoplastic power-law fluids in a hydrocyclone is determined with an analytical solution to a simplified momentum balance equation by the method of perturbation. A numerical solution of the non-linear two-point boundary-value problem by the finite-difference method provides a verification of the perturbation solution. The tangential velocity is found to be controlled by a modified Reynolds number involving the radial velocity at the outer radius of the hydrocyclone and the consistency and flow-behavior indices of the fluid. The radial position of the maximum tangential velocity decreases with an increase in the modified Reynolds number and/or the degree of pseudoplasticity of the fluid. This analysis suggests that improved performance of hydrocyclones may be possible for pseudoplastic fluid systems as the tangential velocity profiles are steeper and the free-vortex zone is extended inwards.
    International Journal of Mineral Processing 07/1987; 20(3-4-20):309-318. DOI:10.1016/0301-7516(87)90073-1
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    ABSTRACT: Some important aspects of fluid-flow phenomena in the air-sparged hydrocyclone have been examined. Profiles of tangential and axial velocity components measured for water in a transparent right vertical cylinder using a laser-doppler anemometer were fitted to a theoretically derived expression for swirl thickness, thus allowing the calculation of turbulent kinematic viscosity and Prandtl's mixing length at different axial positions in the flow field. The size of bubbles formed from a single orifice in the aqueous swirl flow was calculated from first principles and used to compute the size and number density of bubbles expected to form at the porous wall of an air-sparged hydrocyclone. Also the distribution of water and air to the underflow and overflow streams and the residence times of the two phases were considered. The significance of these fluid-flow features in interpreting the actual flotation response of the device is discussed.
    XV International Mineral Processing Congress; 06/1985
  • K.R. Upadrashta, D. Venkateswarlu
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    ABSTRACT: The tangential flow pattern in a 60 mm hydrocyclone operating with power-law fluids is studied by static pressure measurements. Flow pattern constant, n, and inlet velocity ratio, alpha, are computed from the data of 210 experimental runs with water and aqueous carboxymethyl cellulose and aqueous sodium silicate solutions on 10-degree and 20-degree cones. Correlations are obtained for n and alpha in terms of geometrical variables and inlet Reynolds number. The effects of pseudoplasticity and dilatancy of the fluid on n and alpha are noted. Conditions for negative values of n are indicated. The data and correlations for water are compared with those in literature.
  • K.R. Upadrashta, D. Venkateswarlu
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    ABSTRACT: The applicability of hydrocyclone heavy media separation for the enrichment of iron ore, copper ore and fluorspar of fine liberation sizes, is studied. The hydrocyclone used is of 100 mm diameter and 20-degree cone angle. Aqueous suspensions of atomised ferrosilicon stabilised by sodium bentonite constitute the heavy media. The effects of major variables - cone ratio, ore particle size, relative density of heavy medium in underflow, and feed pressure - and their interaction on the separation efficiency are noted on the basis of regression analysis and response surface plots. The crowding theory of classification is extended to heavy media separation. The relationships between relative density of separation, ore recovery in underflow and volume split are indicated. A simple expression for probable error factor is fitted based on literature data. Correlations are presented for volume split and pressure drop factor under conditions of spray and rope types of discharge in underflow.
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    ABSTRACT: The formation of LaCrO3 by the solid-solid reaction of La2O3 and Cr2O3 is studied. The variables covered are: pressure of pelletization (0-128 MN/m2), temperature of sintering (500-1200 C), time of sintering (1-24 h), and mole ratio of Cr2O3 to La2O3 (0.5-2.0). The mass fraction of LaCrO3 in the sintered product is correlated with the variables in the form of a quadratic including terms of interaction between the variables. Response contours are plotted for different pair combinations of the variables. Increase in pelletization pressure is found to favour product formation at low temperatures and to impede at high temperatures. Increase in sintering temperature, time of sintering, and mole ratio of Cr2O3 to La2O3 increases the product formation. An optimum combination of variables that gives a 100 percent yield of pure LaCrO3 is suggested.
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    ABSTRACT: This is the fourth of the four-volume series in chemical technology published by the Chemical Engineering Education Development Centre sponsored by the Department of Education, Government of India. The 11 chapters (authors parenthesized) in this volume cover a broad spectrum of synthetic organic products. Foreword by V.G. Rajadhyaksha. Petroleum (M.G. Menon). Petrochemicals (S.L. Venkiteswaran). Byproducts of coal carbonisation (R. Vaidyeswaran, T.P.S. Rajan). Plastics (R.T. Thampy, B.C. Mitra). Synthetic dyestuffs (S.V. Desai). Drugs and pharmaceuticals (B. Shah); Phytochemicals for drug industry (P.R. Rao). Natural and synthetic rubbers (D.M. Trivedi, K.R. Upadrashta). Man-made fibres - cellulosic and synthetic (J.G. Parikh). Pesticides (R.B. Mitra, S. Ghosh). Explosives (D.S. Sastry). Rocket propellants and other chemicals for space technology (V.R. Gowariker).
    12/1979; Chemical Engineering Education Development Center, Indian Institute of Technology, Madras.
  • Kameswara Rao Upadrashta, Venkateshwar Sreerangam, Ramalingam Kaparthi
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    ABSTRACT: Semi-fluidization is a latest technique in solid-liquid contact operations, awaiting industrial applications. The technique is an outcome of attempts prompted to exploit certain characteristics and to overcome particular limitations of the fixed and fluidized bed contactors. The theoretical advantages of a Mixer-Tubular (M-T) reactor combination for exothermic reactions can easily be realized in a simple semi-fluidized bed reactor, wherein the fluidized portion of the bed acts as a CSTR or a mixer and the packed portion as a plug-flow or tubular reactor. Oxidation of hydrocarbons wherein large quantities of air are utilised, and vapour-phase reactions can be conducted in semi-flidized bed reactors. A design procedure for the semi-fluidized bed reactor for the vapour-phase oxidation of naphthalene to phthalic anhydride is presented to illustrate the advantages of the reactor for exothermic reaction processes.
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    ABSTRACT: This is the third of a four-volume series in chemical technology and its 12 chapters (and authors/coathors) cover various natural organic products. Foreword by S.K. Mukherjee. Starch (R.V. Junnarkar). Sugar (S.N. Gundu Rao, A.C.Raha). Pulp and paper (D.C. Tapadar). Oils,fats and waxes (K.T. Achaya). Soaps and synthetic detergents (C.K. Venkatachalam). Organic surface coatings (K.G. Kudva). Wood and wood chemicals (S.M. Mehta). Perfumes, flavours and cosmetics (S.N. Murthy, D.S. Rao). Biomaterials (M.S. Valiathan, U.R. Shettigara). Leather (N. Ramanathan, V.S. Padmanabhan). Adhesives (M.D. Mathia). Fermentation products (J.V. Bhat).
    09/1977; Chemical Engineering Education Development Centre, Indian Institute of Technology, Madras.
  • Editors: D. Venkateswarlu, K.R. Upadrashta
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    ABSTRACT: This volume is the second of a four-volume series in chemical technology and here is a listing of its 14 chapters (and their authors/coauthors) covering various inorganic products. Foreword by Y. Nayudamma. Industrial gases (S.R.S. Sastry). Industrial acids (C.A. Chandy, J.P. Kapur). Fertilisers (K.S. Chari). Marine chemicals (S.K. Vakil, B.R. Walawalker). Soda ash (R.V. Ramani). Chlorine and caustic alkalis (R.V. Ramani). Selected inorganic chemicals (R.R. Ray). Chemicals for electroplating industries (B.A. Shenoy). Materials for electronics industries (H.J.V. Krishna, K.R. Upadrashta). Electrothermal products (H.V.K. Udupa, V. Aravamuthan, M. Sundaram). Portland cements and other cementing materials (R.R. Hattiangadi). Glass (S. Kumar). Ceramics (R.G. Shah). Refractories (K.R. Upadrashta).
    09/1977; Chemical Engineering Education Development Centre, Indian Institute of Technology, Madras.
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    ABSTRACT: This is the first of a four-volume series in chemical technology being published by the Chemical Engineering Education Development Centre funded by the Department of Education, Government of India. The13 chapters (and authors) in this volume cover various topics related to the chemical and process industry in general with special emphasis on the Indian scenario. Message by Hon'ble S. Nurul Hasan and Forword by A. Ramachandran. Indian chemical industry, an overview (J.V. Rajan, B.D. Tilak). Planning and economics of chemical industry (N.K. Kochar, H.K. Pargal). Technology transfer in chemical industry (C.V.S. Ratnam). Materials of construction (O.P. Kharbanda). Safety in chemical industry (R.V. Betrabet, T.P.S. Rajan). Water (C.A. Sastry). Waste water treatment (B.V. Bhoota, N.D. Chhabria). Fuels (A. Lahiri, H.C. Nandi). Nuclear materials (H.N. Sethna, R.K. Garg). Energy (D. Venkateswarlu, V. Lakshman Rao). Solid waste treatment (D. Venkateswarlu, V. Lakshman Rao). Air pollution (C.A. Sastry). Noise in chemical plants (A. Ramachandraiah, K.R. Upadrashta).
    07/1975; Chemical Engineering Education Development Centre, Indian Institute of Technology, Madras.

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