Journal Publications

Abstract:

The MoTe₂/h-BN heterostructure has attracted considerable attention in recent years due to its unique electrical, thermal, and optical properties, making it a promising candidate for next-generation thermoelectric, spintronic, and optoelectronic applications. However, a comprehensive understanding of its thermal transport behavior remains widely unexplored. In this study, we aim to bridge this gap by providing a detailed analysis of the in-plane phonon thermal conductivity (PTC) of MoTe2/h-BN nanosheet using Non-Equilibrium Molecular Dynamics (NEMD) Simulation. Remarkably, the PTC of MoTe2 is significantly enhanced by approximately 7.3 times, increasing from ~42.55 W/m.K to ~312.50 W/m.K when combined with hexagonal boron nitride (h-BN) to form a van der Waals heterostructure. Our results also reveal that the in-plane phonon transport is strongly influenced by factors such as nanosheet size, system temperature, crystallographic orientation (zigzag and armchair), and vacancy type and concentration. Specifically, increasing the nanosheet size from 20 to 300 nm leads to a ~14.5 times enhancement in PTC, while elevating the temperature from 100 K to 600 K results in a modest 24% decrease. Moreover, introducing vacancies at a concentration of 2% reduces the PTC by 40% for point defects and 42% for edge defects, with point defects causing a more pronounced suppression than edge defects. Additionally, the zigzag orientation consistently exhibits higher thermal conductivity than the armchair direction. These variations are attributed to the complex interplay of various phonon scattering mechanisms that govern thermal energy transport through the nanosheet. To further elucidate the underlying phonon dynamics, the phonon density of states for pristine h-BN, MoTe2, and MoTe2/h-BN have been calculated, offering insights into the vibrational contributions to thermal transport. This comprehensive study deepens our fundamental understanding of phonon thermal transport in MoTe₂/h-BN heterostructures, paving the way for the rational design of next-generation nanodevices with efficient thermal management capabilities. 

Abstract:

A computational analysis has been executed to analyze the combined conduction-mixed convection heat transfer of a rotationally oscillating solid cylinder in a differentially heated square box filled with air. The conjugate mixed convective flow initiates the heat transfer process, where the left-side boundary is isothermally kept to a higher temperature, and the right-side boundary is maintained at a lower temperature. Conduction heat transfer takes place inside the solid cylinder. Navier-Stokes and heat energy conservation equations model the system in the dimensionless pressure-velocity formulation. All these equations are solved via the Galerkin finite element approach. Three different combinations of Grashof (103-105), Reynolds (32–316), and Richardson (0.1–10) numbers are examined to systematically investigate the variations of governing parameters on instantaneous Nusselt numbers and the respective time-averaged values along the hot wall. In each combination, the impacts of the oscillating amplitude and frequency and the variation of cylinder diameter are examined to perform the optimization study. Power spectrum analysis is also done using the Fast Fourier Transform in the frequency domain to visualize the principal frequency of the system. The instantaneous values of the Nusselt number exhibit a wavering pattern over time owing to the recurrent waning and waxing of the thermal boundary layer. For all the cases, the maximum diameter and oscillating amplitude of the cylinder are found to maximize the heat transfer. However, the optimized frequency of the oscillation strongly depends on the selection of the governing parameters. In addition, the principal thermal frequency of the system is determined to be independent of the oscillation frequency. 

Abstract:

A thorough investigation of free convection and entropy generation occurring inside a differentially heated square chamber that is filled with water and divided by a water-saturated, corrugated porous partition is performed in this numerical study. The governing mathematical equations, that describe the flow and heat transfer phenomena for fluid and porous domains, are the Navier-Stokes (modified for the porous domain using the Darcy-Brinkman-Forchheimer model) and thermal energy equations. Those systems of equations are solved using the Galerkin finite element analysis. Parametric changes are carried out for different positions, thicknesses, amplitudes, and frequencies of corrugation of the porous partition, and the corresponding results are quantitatively presented in terms of average Nusselt number along the heated wall and total entropy generation of the entire chamber with increasing Rayleigh number (103 ≤ Ra ≤ 107). Corresponding variations are qualitatively visualized in terms of streamlines and isotherms for comparing the related parametric changes. Furthermore, a comparative analysis is included between the use of porous and solid partitions along with a chamber without any partition. Conclusive results show that using a porous rather than a solid partition can increase the average Nusselt number by 26.28% at Ra = 105 up to a maximum of 565% at Ra = 107. Similarly, lower thickness, higher frequency, and higher amplitude can increase the average Nusselt number by around 37.5%, 2.89%, and 1.17%, respectively. 

Abstract:

The present work aims to investigate flow patterns and control of heat transfer by studying conjugate natural convection behavior inside a dome-shaped permeable chamber enclosing a heat-conducting solid cylinder. The application of this study includes heat transfer equipment such as heat exchangers, steam generator tubes, solar and wind power collector, nuclear reactor, electronic components, etc. The dimensional formulations of Navier-Stokes, thermal energy equations of the porous domains, and the solid cylinder have been used to solve the problem numerically using the finite element technique under realistic boundary conditions. The Darcy-Brinkman-Forchheimer model is used for the porous domain to perform the simulation-based study. Parametric computations have been performed for a large variety of Rayleigh numbers (103 ≤ Ra ≤ 108), several solid materials for the cylinder with varied thermal conductivity (7.99 W/mK ≤ ks ≤ 94.90 W/mK), four different positions (0.25L ≤ yc ≤ L) and different diameters of the cylinder (0.2L ≤ D ≤ 0.40L) inside the chamber, and different inclination angles of the chamber within the range of 0° ≤ θ ≤ 45°. The results in quantitative measurement of average Nusselt number change and qualitative visualization of streamline and isotherms are examined for maximum thermo-fluid performance inside the chamber. The outcomes demonstrate that the dome shape allows better fluid circulation within the chamber, resulting in improved convection heat transfer with a remarkable effect on the overall heat transfer rate of the system under the optimum condition. Besides, both conduction and convection-dominated heat transfer inside the porous cavity strongly depend on the Rayleigh number selection. 

Abstract:

The thermal performance of phase change material (PCM) is significant to latent heat thermal energy storage applications. This paper's current effort is given to investigate the heat transfer pattern and melting process of a PCM (tin) inside a trapezoidal shape enclosure. This study aims to enhance heat transmission and verify the applicability of PCM in thermal storage facilities. The finite element technique is used to examine the transient heat transfer of the system numerically. The enclosure is initially filled with a portion of solid tin, and the remaining is liquid tin. Constant heat flux and fixed temperature are used as heat source and sink, respectively. The result includes qualitative visualizations of temperature and velocity distributions and quantitative thermal responses at a fixed point for relative comparison between PCM and liquid tin. The use of PCM is found advantageous in heat transfer improvement. 

Abstract:

The current effort is devoted to visualizing the natural convection flow behavior inside a dome shape trapezoidal porous media containing a heat-conducting solid cylinder to improve flow structure and natural convection heat transfer. Laminar, steady, incompressible flow behavior has been analyzed keeping the lower wall at high temperature, side walls at low temperature, and upper dome insulated. The porous media consists of fluid with higher thermal conductivity and also highly thermally conducting cylinder material to visualize thermal contour inside the cylindrical region. The finite element method has been applied for solving the non-dimensional form of continuity, Navier-Stokes and energy equation of fluid, and the energy equation of the solid cylinder. Computations have been conducted for a wide range of Grashof numbers (Gr: 103, 104, 105, 106) with a fixed Prandtl number (0.025) since the fluid is considered as mercury. Different materials for the solid cylinder are analyzed for heat transfer of varying thermal conductivity (7.86 ≤ Ks ≤ 35.3). The current study reveals that the Nusselt number can be increased by 4% and 11% respectively in contrast to trapezoidal and rectangular-shaped cavities without a dome. The result also shows that the trapezoidal dome shape facilitates the smoother circulation of fluid throughout the cavity which in turn establishes better natural convection heat transfer.