A study on modeling of boiling heat transfer in core debris bed of SFR

Venkateswarlu S.,Hemanth Rao E.,Prasad Reddy G.V.,Das Sanjay Kumar,Ponraju D.,Venkatraman B. 한국원자력학회 2024 Nuclear Engineering and Technology Vol.56 No.9

In case of a hypothetical severe accident in a Sodium-cooled Fast Reactor (SFR), coolability of the debris bed in the post-accident phase plays a vital role in mitigating the accident and ensuring the structural integrity of the reactor vessel. Few numerical studies are reported in literature, in which the boiling heat transfer in debris bed is expressed as equivalent heat conduction using similarity law between heat conduction and two-phase heat transfer. However, these studies assumed steady state mass conservation for the boiling zone and neglected the gravity force. Hence, a detailed study has been carried out for various particle sizes and porosities of SFR debris to investigate the influence of above considerations. The effect of gravity on debris bed coolability is studied using steady state model of Lipinski, which showed that gravity has a non-negligible effect, for particle size of 0.3 mm and porosity of 0.5. However, the gravitation force was found to have a negligible effect in dryout heat flux estimation for the bottom cooled configuration. A transient numerical model is developed for simulating the boiling phenomena in debris beds and validated with the published experimental results. The assumption of steady state mass conservation is verified by carrying out transient analysis, which indicated early prediction of the dryout inception. For time dependent heat generation case, the unsteady mass conservation predicted higher DHF compared to constant heat generation.

Dependence of the Ferroelectric Properties of Modified Spin-Coating-Derived PZT Thick Films on the Crystalline Orientation

Venkateswarlu Annapureddy,Jong-Jin Choi,Jong-Woo Kim,Byung-Dong Hahn,Cheol-Woo Ahn,Jungho Ryu 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.68 No.12

The effects of crystalline orientation on the ferroelectric properties of lead zirconate titanate (PZT) thick films deposited on (111)-oriented Pt/Ti/SiO2/Si substrates by using a modified spincoating method have been studied. The texture and the microstructure of the thick films were characterized by using X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis, respectively. The XRD results implied that the texture of the PZT films was sensitive to the pyrolysis conditions after spin-coating, but less dependent on the film’s thickness. The texture had mainly a (111)-orientation for pyrolysis temperatures from 330 to 400 C, and changes in the (100)- orientation occurred for pyrolysis temperatures at or above 450 C after annealing at 650 C for 5 min. The formation of a preferred texture could be explained by using the intermetallic phases and the internal stress energies between the substrate and the film. The ferroelectric properties of the PZT films fabricated by using this method have been found to be enhanced as compared to those of the PZT films fabricated by using the conventional spin-coating method and to be correlated to the microstructure of the film.

Core–Shell Ferromagnetic Nanorod Based on Amine Polymer Composite (Fe₃O₄@DAPF) for Fast Removal of Pb(II) from Aqueous Solutions

Venkateswarlu, Sada,Yoon, Minyoung American Chemical Society 2015 ACS APPLIED MATERIALS & INTERFACES Vol.7 No.45

<P>Heavy metal ion removal from wastewater constitutes an important issue in the water treatment industry. Although a variety of nanomaterials have been developed for heavy metal removal via adsorption, the adsorption capacity, removal efficiency, and material recyclability still remain a challenge. Here, we present novel Fe<SUB>3</SUB>O<SUB>4</SUB>@DAPF core–shell ferromagnetic nanorods (CSFMNRs) for the removal of Pb(II) from aqueous solutions; they were prepared by the facile surface modification of twin-like ferromagnetic Fe<SUB>3</SUB>O<SUB>4</SUB> nanorods using a 2,3-diaminophenol and formaldehyde (DAPF)-based polymer. The crystallinity and structure of the Fe<SUB>3</SUB>O<SUB>4</SUB> nanorods were confirmed via X-ray diffraction (XRD). Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) revealed the core–shell morphology and composition of the materials. Pb(II) removal using the prepared Fe<SUB>3</SUB>O<SUB>4</SUB>@DAPF CSFMNRs was assessed, and comparable adsorption capacities (83.3 mg g<SUP>–1</SUP>) to the largest value were demonstrated. A thermodynamic study of the adsorption clearly indicated that the adsorption was exothermic and spontaneous. Due to the ferromagnetic properties with a high saturation magnetization value (56.1 emu g<SUP>–1</SUP>) of the nanorods, the nanorods exhibited excellent reusability with one of the fastest recovery times (25 s) among reported materials. Therefore, the Fe<SUB>3</SUB>O<SUB>4</SUB>@DAPF CSFMNRs can serve as recyclable adsorbent materials and as an alternative to commonly used sorbent materials for the rapid removal of heavy metals from aqueous solutions.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2015/aamick.2015.7.issue-45/acsami.5b07723/production/images/medium/am-2015-07723v_0016.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am5b07723'>ACS Electronic Supporting Info</A></P>

SORET AND CHEMICAL REACTION EFFECTS ON THE RADIATIVE MHD FLOW FROM AN INFINITE VERTICAL POROUS PLATE

VENKATESWARLU MALAPATI,VENKATA LAKSHMI DASARI 한국산업응용수학회 2017 Journal of the Korean Society for Industrial and A Vol.21 No.1

In this present article, we analyzed the heat and mass transfer characteristics of the nonlinear unsteady radiative MHD flow of a viscous, incompressible and electrically conducting fluid past an infinite vertical porous plate under the influence of Soret and chemical reaction effects. The effect of physical parameters are accounted for two distinct types of thermal boundary conditions namely prescribed uniform wall temperature thermal boundary condition and prescribed heat flux thermal boundary condition. Based on the flow nature, the dimensionless flow governing equations are resolved to harmonic and non harmonic parts. In particular skin friction coefficient, Nusselt number and Sherwood number are found to evolve into their steady state case in the large time limit. Parametric study of the solutions are conducted and discussed.

Surfactant-free green synthesis of Fe₃O₄ nanoparticles capped with 3,4-dihydroxyphenethylcarbamodithioate: stable recyclable magnetic nanoparticles for the rapid and efficient removal of Hg(<small>II</small>) ions from water

Venkateswarlu, Sada,Yoon, Minyoung The Royal Society of Chemistry 2015 Dalton Transactions Vol.44 No.42

<P>Mercury is considered one of the most notorious global pollutants due to its high toxicity and widespread use in industry. Although many materials have been developed for the removal of mercury for water purification, most of these materials are difficult to reuse, which may lead to an increase in the mercury handling expense. Therefore, new sustainable materials that can be easily recycled and are highly efficient for the removal of mercury are required. Herein, we report the surfactant-free green synthesis of Fe<SUB>3</SUB>O<SUB>4</SUB> magnetic nanoparticles (MNPs) using a watermelon (<I>Citrullus lanatus</I>) rind extract. The Fe<SUB>3</SUB>O<SUB>4</SUB> MNPs were further functionalized with 3,4-dihydroxyphenethylcarbamodithioate (DHPCT) and applied to the removal of Hg(<SMALL>II</SMALL>). Evaluation of the mercury removal efficiency and the amount adsorbed by DHPCT@Fe<SUB>3</SUB>O<SUB>4</SUB> MNPs demonstrated a high Hg(<SMALL>II</SMALL>) removal efficiency (98%) with a maximum Hg(<SMALL>II</SMALL>) adsorption capacity of 52.1 mg g<SUP>−1</SUP>. Systematic studies of the adsorption mechanism and selectivity suggest that the soft ligand (DHPCT) can preferentially coordinate with the soft metal ion (Hg(<SMALL>II</SMALL>)) resulting in selective mercury removal. The developed DHPCT@Fe<SUB>3</SUB>O<SUB>4</SUB> MNPs were readily recycled several times using an external magnet by exploiting their ferromagnetic character, without a significant decline in the Hg(<SMALL>II</SMALL>) removal efficiency. This study provides a new insight into the preparation of a highly efficient adsorbent for Hg(<SMALL>II</SMALL>) removal by an eco-friendly method.</P> <P>Graphic Abstract</P><P>A 3,4-dihydroxyphenethylcarbamodithioate capped biogenic Fe<SUB>3</SUB>O<SUB>4</SUB> magnetic nanocomposite has been synthesized using a watermelon rind extract for the removal of Hg(<SMALL>II</SMALL>) ions with a facile recyclability. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c5dt03155a'> </P>

Evaluation of ISSR and RAPD Markers for the Detection of Genetic Diversity in Mulberry (Morus spp.)

Venkateswarlu, M.,Nath, B.Surendra,Saratchandra, B.,Urs, S.Raje Korean Society of Sericultural Science 2004 International Journal of Industrial Entomology Vol.9 No.2

The present study was carried out to evaluate the ISSR and RAPD markers for their efficiency as genetic marker systems to establish the relationships between 18 mulberry genotypes. A total of 36 from 56 (64%) RAPD primers and 12 from 48 (25%) ISSR primers produced reproducible amplification patterns. A high proportion of polymorphic bands ranging from 44 to 91% was observed respectively with RAPD and ISSR markers. The average Resolving Power (Rp) of ISSR primers was higher than RAPD primers. The ISSR primers, UBC 825, 868 and 873, and RAPD primers, UBC 712, 720 and 729, possessed the highest Rp values and could in each instance distinguish all the 18 genotypes. Similarity matrix values were estimated based on Jaccards coefficient, considering 109 polymorphic ISSR and 212 polymorphic RAPD bands and two dendrograms were constructed. The dendrograms obtained with ISSR and RAPD markers distinguished the eight exotic genotypes from the ten indigenous (Indian) genotypes. A significant correlation value (r=0.959; p=0.001) for the cophenetic matrix between the RAPD and ISSR matrices was observed. The results indicated that the ISSR and RAPD markers could assist in the differentiation of genotypes and permit the determination of genetic distances that might be exploited by mulberry breeders in improvement programs.

Fungus-derived photoluminescent carbon nanodots for ultrasensitive detection of Hg²⁺ ions and photoinduced bactericidal activity

Venkateswarlu, Sada,Viswanath, Buddolla,Reddy, Ankireddy Seshadri,Yoon, Minyoung Elsevier 2018 Sensors and actuators. B, Chemical Vol.258 No.-

<P><B>Abstract</B></P> <P>Herein, we present a sustainable solvent-free synthetic procedure to produce carbon nanodots from common edible mushrooms (<I>Pleurotus</I> spp.). The resulting mushroom carbon nanodots (MCDs) exhibit stable blue fluorescence with high quantum yield (25%). The MCDs are highly dispersible in water because of the enormous number of oxygen- and nitrogen-containing functional groups on the surface. The MCDs can be used as an effective fluorescent probe for label-free detection of Hg<SUP>2+</SUP> ions (detection limit: 4.13nM). To improve the sensitivity, dihydrolipoic acid was attached to the surface of MCDs, resulting in ultra-sensitivity in Hg<SUP>2+</SUP> ion sensing, with a detection limit as low as 17.4 pM. In addition, the MCDs can be used for the labeling of bacteria and as a photoinduced bactericidal agent. Light irradiation of <I>E. coli</I> treated with MCDs showed excellent bactericidal activity relative to the control. These sustainable and affordable carbon materials are potentially compatible for monitoring toxic metals and as a potent visible-light-responsive bactericidal probe.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A facile chemical free synthesis of carbon nanodots using mushrooms </LI> <LI> Temperature dependent synthesis study for high yield of carbon nanodots </LI> <LI> Very stable MCDs with easy functionalization with DHLA under benign conditions </LI> <LI> Ultrahigh sensitive detection of Hg<SUP>2+</SUP> ions with a detection limit as low as 17.4 pM </LI> <LI> Excellent photo-induced reactive oxygen species generation and bactericidal activity </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Performance and Emission Improvement of Biodiesel Fueled Diesel Engine with Exhaust Gas Recirculation and Ethyl Hexyl Nitrate Additive

K.Venkateswarlu,B.S.R Murthy,V.V Subbarao 보안공학연구지원센터 2015 International Journal of Bio-Science and Bio-Techn Vol.7 No.2

Performance, combustion and emission results of the diesel engine fueled with biodiesel blends with cetane improver as additive are presented in this paper. Cetane improver Ethyl Hexyl Nitrate (EHN) as 0.5% and 1% by volume is added as an additive to diesel-biodiesel blends. Experiments were conducted on a single cylinder, four stroke, and naturally aspirated, direct injection diesel engine with the said fuels using Exhaust Gas Recirculation (EGR) to analyze the performance, combustion and emissions. Experimental results reveal that both cylinder pressure and Heat Release Rate (HRR) decreased with increase in blend percentage and EGR as well. With increase in EHN percentage, CO and HC emissions decreased considerably while NOx decreased marginally. Smoke increases with increase in both EHN and EGR, however, at a particular EGR, blends with cetane improver present the better performance with improved emissions.

Chemical and Biological Aspects of the Sponge Genus Dyside , A Review

Y. Venkateswarlu,P. Ramesh,N. Srinivasa Reddy 한국생약학회 1998 Natural Product Sciences Vol.4 No.3

The chemical constituents anti their biological activities of the sponge genus Dysidea has been reviewed.

Growth of self-textured barium hexaferrite ceramics by normal sintering process and their anisotropic magnetic properties

Annapureddy, Venkateswarlu,Kang, Joo-Hee,Palneedi, Haribabu,Kim, Jong-Woo,Ahn, Cheol-Woo,Choi, Si-Young,Johnson, Scooter David,Ryu, Jungho Elsevier Science Publishers 2017 Journal of the European Ceramic Society Vol. No.

<P><B>Abstract</B></P> <P>In this report a simple and low-cost technique for growing highly textured barium hexaferrite ceramics without the need for flux or seed crystals to achieve grain orientation is demonstrated. Plate-like shaped barium hexaferrite particles were synthesized using a solid-state reaction process and then aligned under a weak magnetic field, followed by uniaxial compaction. The aligned hexaferrite particles appear to serve as seeds, forming textured grains during sintering. The development of texture was verified by X-ray diffraction (XRD), electron backscatter diffraction (EBSD), and vibration sample magnetometer (VSM) measurements. The prepared high-quality hexaferrite ceramics exhibited good anisotropic magnetic properties, comparable to those of single crystal counterparts. A mechanism for the formation of the self-textured grain growth of the barium hexaferrite ceramics, which involves grain boundary and lattice diffusion and interface reaction processes, is proposed.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>