Sreekanth Pannala

Sreekanth Pannala
Saudi Basic Industries Corporation (SABIC) | SABIC · Corporate Research and Development

PhD

About

178
Publications
27,843
Reads
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5,339
Citations
Citations since 2016
33 Research Items
4250 Citations
20162017201820192020202120220200400600800
20162017201820192020202120220200400600800
20162017201820192020202120220200400600800
20162017201820192020202120220200400600800
Additional affiliations
April 2015 - present
SABIC
Position
  • Research Associate
July 2013 - April 2015
Oak Ridge National Laboratory
Position
  • Distingushed Research Staff Member

Publications

Publications (178)
Article
Full-text available
This paper describes a novel reactor for acetylene synthesis by high-temperature thermochemical conversion of paraffin hydrocarbons. The reactor utilizes a conical annular swirling jet, which becomes extremely thin as swirl intensifies. The small thickness provides fast mass, momentum, and heat transfer to facilitate the rapid heating and conversio...
Presentation
Full-text available
This presentation reports on an application of the annular jet vortex contactor (ANJEVOC) for high-temperature pyrolysis of methane. The unique ANJEVOC technology stems from one analytical solution of NSE describing tornado-like flows. Particularly, a conical annular converging-diverging jet develops and becomes very thin and fast as forcing increa...
Article
Stationary or spatio-temporal patterns of catalytic reactions can cause operating challenges in shallow packed-bed reactors with large diameter to depth aspect ratios. Partial ignition patterns were observed in a pilot scale oxidative coupling of methane (OCM) reactor operating on the ignited branch near the extinction point. A three-dimensional (3...
Article
Combustion pyrolysis of natural gas is a promising process for high value-added chemicals such as alkynes and olefins. This work introduces recent experimental and computational studies of a 2.5 kTA (thousand metric ton per year) two-stage combustion pyrolysis unit, and focuses on the role of mixing on pyrolysis. Temperature, pressure, and gas comp...
Article
Majority of electrode materials used for advanced lithium based batteries have well defined chemical composition and particle morphology. The chemistry as well as the microstructure can undergo reversible or irreversible changes under continuous electrochemical charge-discharge cycles. These could have measurable impact on the battery capacity and...
Article
Using the validated simulation model developed in part one of this study for biomass catalytic fast pyrolysis (CFP), we assess the functional utility of using this validated model to assist in the development of CFP processes in fluidized catalytic cracking (FCC) reactors to a commercially viable state. Specifically, we examine the effects of mass...
Article
We report results from a numerical study of multi-time-scale bistable dynamics for CO oxidation on a catalytic surface in a flowing, well-mixed gas stream. The problem is posed in terms of surface and gas-phase sub-models that dynamically interact in the presence of stochastic perturbations reflecting the impact of molecular-scale fluctuations on t...
Article
Multi-stage Adomian decomposition method (MADM) is a proven semi-analytical approximation solution technique for ordinary differential equations (ODEs) which provides a rapidly convergent series by integrating over multiple time intervals. Applicability of MADM for large nonlinear differential algebraic systems (DAEs) is established for the first t...
Article
In this computational study, we model the mixing of biomass pyrolysis vapor with solid catalyst in circulating riser reactors with a focus on the determination of solid catalyst residence time distributions (RTDs). A comprehensive set of 2D and 3D simulations were conducted for a pilot-scale riser using the Eulerian-Eulerian two-fluid modeling fram...
Article
We report results from a computational study of the transition from bubbling to slugging in a laboratory-scale fluidized-bed reactor with Geldart Group B glass particles. For simulating the three-dimensional fluidized-bed hydrodynamics, we employ MFiX, a widely studied multi-phase flow simulation tool, that uses a two-fluid Eulerian-Eulerian approx...
Article
We demonstrate the lithiation process in graphitic anodes using in situ neutron radiography and diffraction in a single-layer pouch cell. The variation in neutron absorption contrast in graphite shows a direct correlation between the degree of lithiation and the discharge potential. The experimental neutron attenuation line profiles across the grap...
Article
In this paper we present a three-dimensional computational formulation for electrode-electrolyte-electrode system of Li-Ion batteries. The physical consistency between electrical, thermal and chemical equations is enforced at each time increment by driving the residual of the resulting coupled system of nonlinear equations to zero. The formulation...
Conference Paper
This paper investigates the applicability of numeric Wazwaz El Sayed modified Adomian Decomposition Method (WES-ADM) for time domain simulation of power systems. WES-ADM is a numerical method based on a modified Adomian decomposition (ADM) technique. WES-ADM is a numerical approximation method for the solution of nonlinear ordinary differential equ...
Article
Severe thermal gradients can develop in Li-ion battery packs and modules especially at high discharge rates and can affect the performance. We report the results of the coupled electrochemical, electrical, and thermal modeling of a lithium-ion battery module comprised of four pouch cells connected either in series or in parallel. Newly developed op...
Article
The impact testing of batteries revealed multiple layers of current collectors come into contact leading to internal short. The local short generates large currents and cause immense heat generation. The dynamics of discharge during this internal short process is not completely understood. In this work we present a three-dimensional electro-chemica...
Article
Full-text available
Silicon (Si) is under consideration as a potential next-generation anode material for the lithium ion battery (LIB). Experimental reports of up to 40% increase in energy density of Si anode based LIBs (Si-LIBs) have been reported in literature. However, this increase in energy density is achieved when the Si-LIB is allowed to swell (volumetrically...
Article
A novel solar receiver that uses solid particles as a heat transfer fluid is being developed at the National Renewable Energy Laboratory for use in concentrating solar power plants. The prototype considered here is enclosed and contains arrays of hexagonal heat transfer tubes that particles flow between. Discrete element method (DEM) simulations we...
Article
The fabrication of 3-D parts from CAD models by additive manufacturing (AM) is a disruptive technology that is transforming the metal manufacturing industry. The correlation between solidification microstructure and mechanical properties has been well understood in the casting and welding processes over the years. This paper focuses on extending th...
Article
Conductive heat transfer to flowing particles occurs when two particles (or a particle and wall) come into contact. The direct conduction between the two bodies depends on the collision dynamics, namely the size of the contact area and the duration of contact. For soft-sphere discrete-particle simulations, it is computationally expensive to resolve...
Article
We propose a wavelet-based scheme that encodes the essential dynamics of discrete microscale surface reactions in a form that can be coupled with continuum macroscale flow simulations with high computational efficiency. This makes it possible to simulate the dynamic behavior of reactor-scale heterogeneous catalysis without requiring detailed concur...
Article
In this work, a discrete element model (DEM) is developed and implemented in the open source flow solver MFiX to simulate the effective thermal conductivity of powder beds for selective laser sintering (SLS) applications, considering scenarios common in SLS such as thin beds, high temperatures, and degrees of powder consolidation. Random particle p...
Article
Additive manufacturing (AM), widely known as 3D printing, is a method of manufacturing that forms parts from powder, wire or sheets in a process that proceeds layer by layer. Many techniques (using many different names) have been developed to accomplish this via melting or solid-state joining. In this review, these techniques for producing metal pa...
Article
Full-text available
Batteries are highly complex electrochemical systems, with performance and safety governed by coupled nonlinear electrochemical-electrical-thermal-mechanical processes over a range of spatiotemporal scales. We describe a new, open source computational environment for battery simulation known as VIBE - the Virtual Integrated Battery Environment. VIB...
Article
Full-text available
Additive manufacturing (also known as 3D printing) is considered a disruptive technology for producing components with topologically optimized complex geometries as well as functionalities that are not achievable by traditional methods. The realization of the full potential of 3D printing is stifled by a lack of computational design tools, generic...
Article
Lithium-ion batteries are highly complex electrochemical systems whose performance and safety are governed by coupled nonlinear electrochemical-electrical-thermal-mechanical processes over a range of spatiotemporal scales. Gaining an understanding of the role of these processes as well as development of predictive capabilities for design of better...
Article
Full-text available
Hybrid electric vehicles (HEVs) have attracted considerable attention due to their potential to reduce fuel consumption and emissions. The objective of this paper is to enhance our understanding of the associated tradeoffs among the HEV subsystems, e.g., the engine, the motor, and the battery, and investigate the related implications for fuel consu...
Article
Recent advancements in high-performance parallel computing platforms and parallel algorithms have significantly enhanced the opportunities for real-time power system protection and control. This paper investigates application of Parareal in time algorithm for fast dynamic simulations. Parareal algorithm belongs to the class of temporal decompositio...
Conference Paper
Abstract—In this paper, the merits of Adomian Decomposition Method (ADM) have been investigated for the time domain simulation of multi-machine power systems. ADM is an analytical approximation method for the solution of linear, nonlinear, deterministic and stochastic operator equations. It approximates the nonlinearities in the equations using Ado...
Article
A fundamental continuum model for conductive heat transfer between an immersed boundary and flowing particles is developed. The model is derived for systems where conduction through the interstitial gas between nearby surfaces is the dominant heat transfer mechanism. Conductive heat transfer depends on the thermal properties of the solids and gas p...
Article
Selective laser sintering (SLS) is an additive manufacturing technique for rapidly creating parts directly from a computer-aided design (CAD) model by using a laser to fuse successive layers of powder. However, better understanding of the effect of particle-level variations on the overall build quality is needed. In this work, we investigated these...
Article
3-D architectures are electrode and battery configurations that are non-planar configurations and offer the potential for greatly improved performance, particularly in terms of volumetric energy density, compared to traditional planar (1-D along the cell-sandwich and 2-D along the plane of the electrodes) configurations (or their derivatives). 1, 2...
Article
The performance of lithium-ion batteries is limited by suboptimal energy density and power capability. A feasible approach is designing 3D electrode architectures where lithium ion transport in the electrolyte and active material can be optimized for improving the energy/power density. In this study, the influence of active material morphology and...
Conference Paper
Full-text available
In this paper, we investigate the trade-offs among the subsystems of a hybrid electric vehicle (HEV), e.g., the engine, motor, and the battery, and discuss the related implications for fuel consumption and battery capacity and lifetime. Addressing this problem can provide insights on how to prioritize these objectives based on consumers' needs and...
Conference Paper
In collaboration with a major automotive manufacturer, we are using computational simulations of in-cylinder combustion to understand the multi-scale nonlinear physics of the dilute stability limit. Because some key features of dilute combustion can take thousands of successive cycles to develop, the computation time involved in using complex model...
Conference Paper
Li-ion batteries are known to have significant heating at high C-rates, such as 5C, 10C, and higher as demanded in automotive and other applications. The cell temperature will increase dramatically and additional cooling is required. In order to cool down the core temperature to keep the Li-ion cells within the optimum operating temperatures of 20-...
Conference Paper
Today, most of the battery pack simulations are conducted for design and analysis of the cooling channels to address non-uniform temperature distribution that lead to loss of performance and life. This non-uniformity could lead to different ageing of the cells depending on their location within the pack. This could subsequently trigger undesirable...
Conference Paper
We present the computational implementation and results of a unified formulation across the electrode-electrolyte-electrode system. This formulation utilizes a rigorous volume averaging approach typical of multiphase formulation1, 2 and recently extended to supercapacitors3. Unlike previously used methods for Lithium ion batteries based on a segreg...
Conference Paper
Most deformation models for Li-ion batteries are based on device-level empirical fits to the integral battery responses under the external and internal loadings. One of the main obstacles to establishing physics-based mechanical models formulations for Li-ion batteries is a lack of insight into the underlying kinematic micro-mechanisms of deformati...
Article
Two-dimensional (2D) numerical simulations have been widely reported in the literature for qualitative, even quantitative, study of the complex gas–solids flow behavior in circulating fluidized bed (CFB) risers. It is generally acknowledged that there exist quantitative differences between 2D and three-dimensional (3D) numerical simulations. Howeve...
Article
In this work, a detailed grid refinement study was carried out for two well-documented circulating fluidized bed (CFB) systems with the focus on grid convergence of 2D numerical simulations. It is demonstrated that the grid convergence of numerical simulations depends on the flow field variable chosen for verification. For axial pressure gradient,...
Article
We present the computational implementation and results of a unified formulation across the electrode-electrolyte-electrode system. This formulation utilizes a rigorous volume averaging approach typical of multiphase formulation 1, 2 and recently extended to supercapacitors ³ . Unlike previously used methods for Lithium ion batteries based on a seg...
Article
Li-ion batteries are known to have significant heating at high C-rates, such as 5C, 10C, and higher as demanded in automotive and other applications. The cell temperature will increase dramatically and additional cooling is required. In order to cool down the core temperature to keep the Li-ion cells within the optimum operating temperatures of 20-...
Article
Most deformation models for Li-ion batteries are based on device-level empirical fits to the integral battery responses under the external and internal loadings. One of the main obstacles to establishing physics-based mechanical models formulations for Li-ion batteries is a lack of insight into the underlying kinematic micro-mechanisms of deformati...
Article
Today, most of the battery pack simulations are conducted for design and analysis of the cooling channels to address non-uniform temperature distribution that lead to loss of performance and life. This non-uniformity could lead to different ageing of the cells depending on their location within the pack. This could subsequently trigger undesirable...
Article
Multivalent conversion-based binary transition metal (TM) compounds have recently gained significant attention due to their higher specific capacity compared to conventional intercalation-based lithium-ion materials, due to their multiple red-ox states contributing towards transfer of > 1 lithium per transition metal atom. ¹⁻² However, harvesting r...
Article
Understanding and quantifying the changes in chemical composition as well as morphology of battery materials under electrochemical cycling is fundamental to their long cycle life and safety ¹⁻² . This is particularly true for high energy density lithium-manganese rich cathodes which transitions from a high voltage layered–layered phase to a defect...
Article
A generalized three dimensional computational model based on unified formulation of electrode–electrolyte system of an electric double layer supercapacitor has been developed. This model accounts for charge transport across the electrode-electrolyte system. It is based on volume averaging, a widely used technique in multiphase flow modeling (1 and...
Conference Paper
Introduction Catalytic upgrading3,10 of biomass pyrolysis vapors prior to condensation has recently received attention as a promising strategy for improving the compatibility of bio-oil with conventional processing infrastructure. Riser reactors, staples of the petroleum processing industry, are commonly used for FCC (fuel catalytic cracking) and...
Article
Recently, we investigated the role of electrode architecture on the capacity retention and hysteresis of iron (II and III) fluoride conversion compound. ¹ The unique electrode architecture consists of nanometer sized iron fluoride particles (~ 25-50nm) coated with multilayer graphitic platelets and bound to an electronic backbone comprising of an i...
Article
In this work, a detailed grid refinement study was carried out for two well-documented circulating fluidized bed (CFB) systems with the focus on grid convergence of 2D numerical simulations. It is demonstrated that the grid convergence of numerical simulations depends on the flow field variable chosen for verification. For axial pressure gradient,...
Article
Two-dimensional (2D) numerical simulations have been widely reported in the literature for qualitative, even quantitative, study of the complex gas-solids flow behavior in circulating fluidized bed (CFB) risers. It is generally acknowledged that there exist quantitative differences between 2D and three-dimensional (3D) numerical simulations. Howeve...
Article
Simple kinetic models of carbon nanotube growth have been able to successfully link together many experimental parameters involved in the growth of carbon nanotubes for practical applications including the prediction of growth rates, terminal lengths, number of walls, activation energies, and their dependences on the growth environment. The implica...
Article
In this paper we report on the development and demonstration of physically consistent three-dimensional models for Lithium Ion Battery (LIB) cells. The discharge behavior of a LIB is a multiphysics and multiscale problem that is simulated using coupled models for thermal, electrical, and electrochemical phenomena. The individual physics models and...
Article
Full-text available
We report novel electrode architectures for high capacity multivalent conversion compounds such as iron (II and III) fluoride. The material and electrode design approach addresses the intrinsically poor transport and diffusion kinetics associated with ionic solids such as iron fluorides and significantly improves their electrochemical and cycle lif...
Article
We have investigated a novel approach wherein we undertake surface fluorination of nanometer sized Fe3O4 conversion compound into corresponding oxyfluoride with the goal toward enhancing their energy density as well electrochemical performance stability. This is achieved by using direct fluorination of nano-Fe3O4 in a fluidized bed reactor under co...
Article
The kinetics and mechanisms of graphene growth on Ni films at 720-880 °C have been measured using fast pulses of acetylene and real-time optical diagnostics. In situ UV-Raman spectroscopy was used to unambiguously detect isothermal graphene growth at high temperatures, measure the growth kinetics with ∼1 s temporal resolution, and estimate the frac...