M.Sc. Research (2023-2025)  

Phonon thermal conductivity and vacancy engineering of the MoTe2/h-BN van der Waals heterostructure

Supervisor: Dr. AKM Monjur Morshed, Professor, Dept. of ME, BUET

Collaborators: Sadia Tasnim, Priom Das

• Calculated in-plane phonon thermal conductivity (PTC) of Molybdenum Di Telluride (MoTe2)/Hexagonal Boron Nitride (h-BN) heterostructures using molecular dynamics simulations.

• Provided molecular-level insights into the impacts of nanosheet size, crystallographic orientations, defect engineering, and system temperature on nanoscale heat conduction in MoTe2/h-BN van der Waals heterostructures for energy-efficient nanoelectronics applications.

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. 

B.Sc. Research (2018-2023) 

Estimation of Comprehensive Thermal Performance for Conjugate Natural Convection Inside a Dome-Shaped Porous Chamber Holding a Solid Cylinder

Supervisor: Dr. Sumon Saha, Professor, Dept. of ME, BUET

• Conducted CFD simulations to present the first comprehensive analysis of conjugate natural convection in a dome-shaped porous chamber with an internal solid cylinder, offering new insights into heat transfer mechanisms in complex geometries.

• Findings contribute to the design and optimization of advanced thermal systems, with potential applications in energy storage, electronic cooling, and porous medium engineering.

Abstract

The present work aims to investigate flow pattern and heat transfer by studying conjugate natural convection behavior inside a dome-shaped permeable chamber enclosing a heat-conducting solid cylinder. Laminar, incompressible, continuous, steady flow pattern has been observed inside the chamber by maintaining the bottom wall at a constant heat flux condition, inclined walls at an ambient condition, and the top dome insulated. The permeable medium is made up of a fluid (water) with sodalime-silicate glass bends. The dimensional formulations of continuity, momentum, and thermal energy equations of the porous domains, and the solid cylinder's energy equation have been utilized to solve the problem numerically using the finite element technique under realistic boundary conditions. Parametric computations have been performed for a large variety of Rayleigh numbers (103 ≤ Ra ≤ 108). For heat transmission, several solid materials with varied thermal conductivity (7.99 W/mK ≤ ks ≤ 94.90 W/mK), for the cylinder are selected. Simulations are also performed for four different positions (xc = 0.5L, 0.25L ≤ yc ≤ L) and different diameters of the cylinder (0.2L ≤ D ≤ 0.40L) inside the chamber. The research is performed for a constant Darcy number and porosity factor 4.04 × 10-6 and 0.38 respectively. Thermal performance has been analyzed for different inclination angles of the chamber within the range of 0° ≤ θ ≤ 45°. The results in terms of quantitative measurement of average Nusselt number change as well as 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 improved convection heat transfer with remarkable effect on the overall heat transfer rate of the system under the optimum condition.

B.Sc. Research (2018-2023) 

Natural convection and entropy generation inside a square chamber divided by a corrugated porous partition

Supervisor: Dr. Sumon Saha, Professor, Dept. of ME, BUET

Collaborator: Niloy Deb

• The study explores natural convection and entropy generation in a square chamber separated by a corrugated porous partition, highlighting how partition geometry influences flow behavior and thermal performance.

• The results provide valuable guidelines for optimizing energy efficiency and minimizing irreversibility in thermal systems that use porous structures.

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.