Numerical and experimental study on biased tube temperature problem in tangential firing boiler

Akkinepally, Bhargav,Shim, Jaesool,Yoo, Kisoo Elsevier 2017 Applied thermal engineering Vol.126 No.-

<P><B>Abstract</B></P> <P>In this study, a numerical and experimental investigation on the flow field in a 500-MW unit of a tangentially fired boiler has been performed to understand the effect of residual swirl on the temperature distribution and inconsistency of flow velocity in the crossover pass. The k–k<SUB>L</SUB>–ω turbulence model was used in this study to analyse the possible formation of transition flow in the tangential firing boiler. Furthermore, 1D and 3D hybrid modelling were used for the simulation of the convective heat transfer in the boiler tube assembly. The commercially available code ANSYS Fluent and COMSOL were used for the studies, respectively. The numerical results for the velocity profile and residual swirl in the boiler were validated using the experimental results from the cold air velocity test, in which the flow velocity was directly measured in the full-scale boiler. The computational results agreed well with the experimental findings. Furthermore, from a comparison of the simulation and experiment, it was found that the biased gas flow induces non-uniform tube temperatures at the crossover pass area of the tangential firing boiler. These results aid in the detailed study of the residual swirl effects on the temperature or flue gas at various locations of the boiler. This study indicates that a non-uniform tube temperature at the crossover pass is an inherent problem resulting from residual swirl in the tangential firing boiler. Therefore, the pulverised coal burner should be fine-tuned to avoid tube rupture due to local overheating.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A full-scale CFD simulation was performed for a 500-MW unit of a tangentially fired boiler to determine the flow behaviour. </LI> <LI> The CFD model was validated with experimental results from the cold air velocity test. </LI> <LI> Temperatures of the boiler tube were measured directly in commercial tangential firing boilers. </LI> <LI> Biased temperature profile of the steam and tube is attributed to the non-uniform velocity of the flue gas. </LI> </UL> </P>

LiZr₂(PO₄)₃ 고체 전해질 Li-air 전지의 Al 도핑에 따른 리튬 이온 수송 특성 : 실험 및 분자 동역학 연구

Bhargav Akkinepally,Neelakanta Reddy Ithereddy,Jaesool Shim(심재술) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.4

지난 수십 년에서 NASICON의 결정 성 그룹은 높은 이온 전도성을 위해 급격한 발전을 이루고 미래의 리튬 전지의 유망한 후보가 되었습니다. 이 연구에서는 입계 저항, 이온 확산 및 순수 LZP (리튬 지르코늄 포스페이트)의 전도도에 대한 Al 도펀트의 체계적인 이중 효과에 초점을 맞추고있었습니다. LAMMPS (큰 원자 / 분자 초 병렬 시뮬레이터) 도구는 위의 수송 특성에 대한 불순물의 영향을 결정하기 위해 사용되어 있었습니다. 이러한 시뮬레이션은 원자 버킹엄 잠재력을 기반으로 합니다. 리튬 공기 전지의 Li_1+xAl_xZr_2-x (PO₄)₃ 고체 전해질의 프레임 워크는 다양한 온도에서 분석되고 있습니다. 계산 결과는 실험 결과와 일치하고 있기 때문에 계산 코드를 확인합니다. Al 도핑은 Li 이온 전도성과 확산 계수 모두에 크게 영향을 줍니다. In the last few decades, crystalline group of NASICON due to its high ionic conductivity have experienced a sharp development and became a promising candidate for the future lithium batteries. In this research, we focused on a systematic dual effect of Al dopant on the grain boundary resistance, ionic diffusion and the conductivity on the pure LZP (Lithium Zirconium Phosphate). LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator) tool had been used to determine the dopant effect on the above mentioned transport properties. These simulations were based on the interatomic Buckingham potentials. The framework of Li_1+xAl_xZr_2-x(PO₄)₃ solid electrolyte for Li-air batteries have been analyzed at different temperatures. The computational results are in agreement with the experimental results and hence validating the computational code. The Al doping significantly effects both the Li-ion conductivity and the diffusivity.

Artificial Intelligence assistive prediction of ionic conductivity in Li-based superionic conductors: A Molecular Dynamics Simulations validation

Bhargav Akkinepally,Jaesool Shim 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11

The world is moving towards the renewables and Li-batteries play a vital role in that green future. Owing to the safety issues of liquid electrolytes, solid electrolytes are in demand to replace the already existing Li-ion battery infrastructure. This necessitates the research efforts into discovering suitable solid electrolytes which have higher ionic conductivities. As the process of screening of electrolytes by trial and error is time consuming and resource intensive, thereby demands the development of appropriate machine learning algorithms. In this work, we focus on developing a novel machine learning algorithm to predict the ionic conductivity of Li Super Ionic Conductors (LiSICON). The elemental features derived from the unit cell information and the atomic properties of the elements of 40 LiSICON compounds. The logistic regression model we developed is capable of classifying in which category the compound falls into from either good, average or bad with an accuracy of over 88 %. The test data results are validated with the molecular dynamics simulations. These findings exhibit the benefits of using such a tool in the preliminary screening of potential solid electrolytes with the existing data which helps in focusing only on the promising candidates thereby reducing the time consumption for experimentalists.

Facile one-step synthesis of pellet-press-assisted saddle-curl-edge-like g-C₃N₄ nanosheets for improved visible-light photocatalytic activity

Babu, Bathula,Akkinepally, Bhargav,Shim, Jaesool,Yoo, Kisoo Elsevier 2019 CERAMICS INTERNATIONAL Vol.45 No.12

<P><B>Abstract</B></P> <P>Graphitic carbon nitride (g-C<SUB>3</SUB>N<SUB>4</SUB>) has attracted increasing interest as a visible-light-active photocatalyst. In this study, saddle-curl-edge-like g-C<SUB>3</SUB>N<SUB>4</SUB> nanosheets were prepared using a pellet presser (referred to as g-CN P nanosheets). Urea was used as the precursor for the preparation of g-C<SUB>3</SUB>N<SUB>4</SUB>. Thermal polymerization of urea in a pellet form significantly affected the properties of g-C<SUB>3</SUB>N<SUB>4</SUB>. Systematic investigations were performed, and the results for the modified g-C<SUB>3</SUB>N<SUB>4</SUB> nanosheets are presented herein. These results were compared with those for pristine g-C<SUB>3</SUB>N<SUB>4</SUB> to identify the factors that affected the fundamental properties. X-ray diffraction analysis and high-resolution transmission electron microscopy revealed a crystallinity improvement in the g-CN P nanosheets. Fourier-transform infrared spectroscopy provided clear information regarding the fundamental modes of g-C<SUB>3</SUB>N<SUB>4</SUB>, and X-ray photoelectron spectroscopy (XPS) peak-fitting investigations revealed the variations of C and N in detail. The light-harvesting property and separation efficiency of the photogenerated charge carriers were examined via optical absorption and photoluminescence studies. The valence band edge and conduction band edge potentials were calculated using XPS, and the results indicated a significant reduction in the bandgap for the g-CN P nanosheets. The Brunauer–Emmett–Teller surface area increased for the g-CN P nanosheets. The photocatalytic degradation performance of the g-CN P nanosheets was tested by applying a potential and using the classical dye Rhodamine B (RhB). The RhB dye solution was almost completely degraded within 28 min. The rate constant of the g-CN P nanosheets was increased by a factor of 3.8 compared with the pristine g-C<SUB>3</SUB>N<SUB>4</SUB> nanosheets. The high crystallinity, enhanced light absorption, reduced bandgap, and increased surface area of the saddle-curl-edge-like morphology boosted the photocatalytic performance of the g-CN P nanosheets.</P>

Mn-doped ZrO₂ nanoparticles prepared by a template-free method for electrochemical energy storage and abatement of dye degradation

Reddy, Chandragiri Venkata,Reddy, I. Neelakanta,Akkinepally, Bhargav,Harish, V.V.N.,Reddy, Kakarla Raghava,Jaesool, Shim Elsevier 2019 CERAMICS INTERNATIONAL Vol.45 No.12

<P><B>Abstract</B></P> <P>A template-free technique was used to prepare pure and Mn-doped ZrO<SUB>2</SUB> photocatalyst samples in this study. The effect of doping on the structural, optical, photocatalytic, and supercapacitor properties were investigated. X-ray diffraction analysis revealed that the prepared samples had a tetragonal crystal structure. The optical band gap was narrowed due to the incorporation of Mn ions. The photocatalytic activity of methyl orange organic dye degradation with the Mn-doped ZrO<SUB>2</SUB> sample was examined under visible-light irradiation. The doped sample showed 83% of dye degradation after 100 min of irradiation. Cyclic voltammetry was used to study the supercapacitor properties, and the doped samples exhibited capacitance seven times greater than that of the pure sample.</P>

(${\beta}$-Galactoside Prodrugs of Doxorubicin for Application in Antibody Directed Enzyme Prodrug Therapy/prodrug Mono Therapy

Devalapally, Harikrishna,Navath, Raghavendra Swamy,Yenamandra, Venkateshwarlu,Akkinepally, RaghuRam Rao,Devarakonda, Rama Krishna 대한약학회 2007 Archives of Pharmacal Research Vol.30 No.6

Anthracycline antibiotics, particularly doxorubicin and daunorubicin, have been used extensively in the treatment of human malignancies. However cardiotoxicity and multidrug resistance are significant problems that limit the clinical efficacy of such agents. Rational design to avoid these side effects includes strategies such as drug targeting and prodrug synthesis. Described here are the synthesis and preliminary biological evaluation of the enzymatically activated two new prodrugs (6 & 11) of doxorubicin. These prodrugs were designed as potential candidates for selective chemotherapy in ADEPT or PMT strategies. They are constituted of a galactose moiety, a spacer and the cytotoxic drug and they differ by the type of spacer. The prodrugs were stable in a buffer, and the in vitro studies showed good detoxification and hydrolysis kinetics. As prodrug 11 was readily hydrolyzed, this could be a valuable candidate for further development.

β-Galactoside Prodrugs of Doxorubicin for Application in Antibody Directed Enzyme Prodrug Therapy/Prodrug MonoTherapy

HariKrishna Devalapally,Raghavendra Swamy Navath,Venkateshwarlu Yenamandra,RaghuRam Rao Akkinepally,Rama Krishna Devarakonda 대한약학회 2007 Archives of Pharmacal Research Vol.30 No.6

Anthracycline antibiotics, particularly doxorubicin and daunorubicin, have been used extensively in the treatment of human malignancies. However cardiotoxicity and multidrug resistance are significant problems that limit the clinical efficacy of such agents. Rational design to avoid these side effects includes strategies such as drug targeting and prodrug synthesis. Described here are the synthesis and preliminary biological evaluation of the enzymatically activated two new prodrugs (6 & 11) of doxorubicin. These prodrugs were designed as potential candidates for selective chemotherapy in ADEPT or PMT strategies. They are constituted of a galactose moiety, a spacer and the cytotoxic drug and they differ by the type of spacer. The prodrugs were stable in a buffer, and the in vitro studies showed good detoxification and hydrolysis kinetics. As prodrug 11 was readily hydrolyzed, this could be a valuable candidate for further development.