Deepak Kumar

Separation of no-carrier-added astatine radionuclides from α-particle irradiated lead bismuth eutectic target: A classical method

Possibility of separation of no-carrier-added (NCA) astatine radionuclides from the bulk lead-bismuth-eutectic (LBE) target was explored in a simple way in the laboratory scale. A LBE target was irradiated by 40MeV α-particles delivered from a cyclotron facility, India. Quantitative analysis of the irradiated target indicated the production of 210,209At, 207Po radionuclides in the target matrix. The 210,209At radionuclides were separated by precipitation of bulk Pb, Bi and NCA radiotoxic Po radionuclides.

Opposing buoyancy characteristics of Newtonian fluid flow around a confined square cylinder at low and moderate Reynolds numbers

ABSTRACT The influence of opposing-buoyancy mixed convection from a square cylinder in a vertical channel has been studied at Reynolds numbers (Re) = 1–100, Richardson numbers (Ri) = 0 to −1, and blockage ratios (β) = 10–50% for air as a working fluid. The onset of a steady to a time-periodic regime is found for Ri = 0 (at Re = 35, 65, 74, and 62), Ri = −0.5 (at Re = 12, 39, 48, and 54), and Ri = −1 (at Re = 9, 30, 39, and 50) for β = 10%, 25%, 30%, and 50%, respectively. The initiation of flow separation is also determined. Finally, the correlations of Strouhal number, drag coefficient, and the Colburn heat transfer factor were obtained.

Computations of Newtonian fluid flow around a square cylinder near an adiabatic wall at low and intermediate Reynolds numbers: Effects of cross-buoyancy mixed convection

ABSTRACT The effects of cross-buoyancy mixed convection from a square cylinder in the proximity of a plane wall are studied for Reynolds number (Re) = 1–100, Richardson number (Ri) = 0–2, and gap ratio (G) = 0.25–1 at Prandtl number (Pr) = 0.7. The flow observed is steady for G = 0.25 and 0.5. The transition from a steady to a time-periodic system is observed for G = 1, and it is found at Re = 56, 60, and 74 for Ri = 0, 1, and 2, respectively. With increasing G and/or Ri, the drag coefficient and average Nusselt number increase for all Re values studied and the lift coefficient decreases with increasing Ri except at Re = 1. Maximum heat transfer augmentation is found about 89% at G = 0.5 (Re = 20, Pr = 0.7, Ri = 0) with respect to the corresponding value at G = 0.25 (Re = 20, Pr = 0.7, Ri = 0). Lastly, the correlations of drag coefficient and heat transfer have been obtained.

Production of no-carrier-added 97Ru from 11B-activated natural yttrium target and its subsequent separation using liquid–liquid extraction

ABSTRACT Production of no-carrier-added (NCA) 97Ru was investigated from the 11B-induced reaction on the natural Y target. Bombardment of 40 MeV B-beam on the natY foil (2.8 mg/cm2) produced 17.4 kBq activity of 97Ru in 7.5 h along with the minute production of 96Tc and 93mMo. Separation of NCA 97Ru from the bulk was performed by liquid–liquid extraction (LLX). Liquid cation exchanger di-(2-ethylhexyl)phosphoric acid (HDEHP) dissolved in cyclohexane was used in combination with the aqueous solution of HNO3. Optimum separation of NCA 97Ru from the bulk Y was achieved at 1% HDEHP and 10−5 M HNO3 that led to a high separation factor of ~105.

Effects of shear-thinning nature and opposing buoyancy from a square geometry in a confined framework

ABSTRACT Numerical computations were brought up to study the effect of opposing buoyancy mixed convection (Ri = 0 to − 1) flow of power law shear-thinning fluids past a confined cooled square bluff body at Prandtl numbers (Pr) = 1, 50 and Reynolds numbers (Re) = 1–40. Irrespective of the n, Ri, Pr, and Re, the flow separation is delayed with increasing confinement (β). The vortex shedding and flow separation start earlier for shear-thinning fluids than Newtonian fluid. For opposing buoyancy (Ri < 0), the vortex shedding starts earlier on increasing Pr (except for n = 0.2, Ri = −1). Also, the periodic unsteady transition appears at some higher value of Re on increasing Ri for fixed Pr. The drag coefficient (CD) value reduces with the decrease in n, whereas the maximum CD is noted for Newtonian fluids. The maximum augmentation in the heat transfer was reached about 9 and 36% on comparing with Newtonian fluids and forced convection case, respectively, and also the corresponding maximum compression in heat transfer was found about 15 and 5%, respectively. The numerical results have also been correlated for CD and the Colburn jh factor values for various Re, Pr, Ri, and n. In surplus, the effects of wall confinement ranging from β = 25 to 50% on flow separation and engineering output parameters were studied in a steady regime.

Effect of Wall Proximity on the Flow Over a Heated Square Bluff Body

The two-dimensional numerical simulations of Newtonian fluid stream about a square bluff body have been studied in an unconfined configuration in addition in the propinquity of a plane wall. The comparison of flow and heat transfer constraints is done with the pure unconfined flow about a square obstacle. The set of physical constraints considered as Reynolds numbers (Re) = 100, 120 and Prandtl number (Pr) = 0.7 (air) at varying values of gap ratios (g). The values of drag and lift coefficients, and average Nusselt number are computed. The present study shows that on increasing the gap ratio, the drag coefficient is acquired to be the highest for the gap ratio of unity and it is observed the lowest for the unconfined case. Lift coefficient decreases and average Nusselt number increases with increasing gap ratio, but opposite effects are observed for the unconfined case. The flow becomes steady at low gap ratio, but on increasing gap ratio the flow behavior changes to periodic unsteady. The augmentation in heat transfer is found about 35 % for g = 1, with respect to the corresponding value for the unconfined case.

Mathematical modeling of brown stock washing problems and their numerical solution using MATLAB

Abstract The mechanism of the displacement washing of the bed of pulp fibers is mathematically modeled by the basic material balance equation. Non-linear Langmuir type adsorption isotherm is used to describe the relationship between the concentration of the solute in the liquor and concentration of the solute on the fibers. In the present study, the numerical solutions are obtained of the displacement washing model for multistage in counter current manner. For the numerical solution “pdepe” solver in MATLAB is applied on the axial domain of the system of governing partial differential equations. Numerical solutions thus obtained are in good agreement with the results of earlier workers. The technique used in the present investigation is simple, elegant and convenient for solving two point boundary value problems with varying range of parameters.

Analysis of Parametric Effects on Efficiency of the Brown Stock Washer in Paper Industry Using MATLAB

In the present paper, the effects of cake thickness and time on the efficiency of brown stock washer of the paper mill are studied by using mathematical model of pulp washing for the species of sodium and lignin ions. The mechanism of the diffusion‐ dispersion washing of the bed of the pulp fibers is mathematically modeled by the basic material balance and adsorption isotherm is used to describe the equilibrium between the concentration of the solute in the liquor and concentration of the solute on the fibers. To study the parametric effect, numerical solutions of the axial domain of the system governed by partial differential equations (transport and isotherm equations) for different boundary conditions are obtained by the “pdepe” solver in MATLAB source code. The effects of both the parameters are shown by three dimensional graphical representation as well as concentration profiles.