Dr. Deepak Selvakumar Ramachandran is a Research Scientist in the Department of Mechanical and Nuclear Engineering at Khalifa University, Abu Dhabi, UAE, a role he has held since October 2022. He earned his Ph.D. in Mechanical Engineering from the Indian Institute of Technology Indore in 2018. Following his doctorate, he was awarded the International Talent Introduction Fellowship to join the School of Energy Science and Engineering at Harbin Institute of Technology (HIT), China, as a Research Associate (2019-2020). He continued his work at HIT as an Assistant Professor through the National Science Foundation of China (NSFC) Fellowship (2020-2021). He later served as a Research Fellow at the Indian Institute of Technology Madras through the Institute Post-Doctoral Fellowship (2021) and as a Research Professor in the Advanced Thermal Systems Laboratory at Chung-Ang University, South Korea (2021-2022). His research expertise lies in numerical modeling of complex flow and heat transfer phenomena, including solid-liquid phase change, nanofluid flow, electrohydrodynamic (EHD) flows, and microchannel flows, with a particular focus on applications in energy storage and heat transfer intensification.
Design of electrohydrodynamic (EHD) flow assisted Latent Heat Thermal Energy Storage (LHTES) Systems
Phase change material (PCM) based latent heat thermal energy storage (LHTES) is a popular technique owing to its high energy storage density, scalability, and near-constant temperature operation. However, common PCMs suffer from low intrinsic thermal conductivity, limiting the energy storage rate of the LHTES units. To address this issue, a novel design of an LHTES module that is assisted with charge injection-induced electrohydrodynamic (EHD) flow to enhance the charging rate is proposed. The evolution of critical parameters such as total liquid volume fraction, mean kinetic energy density and mean temperature are mapped as a function of time. The key objective is to evaluate the performance under different (weak, medium, and strong) charge injection regimes. The EHD flow intensifies the flow velocity, alters the flow structure, and increases the heat transfer. The melting process gets more uniform and faster with the assistance of EHD flow. EHD flow at strong charge injection regime nullifies the effect of gravity and leads to equal performance irrespective of the orientation. Shorter melting times and increased power storage capacity are achieved in the presence of EHD flow.
Development of EHD assisted heat sink for electronic cooling applications
The research work introduces a novel approach to enhance the thermal performance of a phase change material (PCM) heat sink by integrating charge injection-induced electrohydrodynamic (EHD) flow. The solid–liquid phase change process is modeled using a stationary grid approach based on the enthalpy-porosity method. Based on the finite-volume method (FVM) within the OpenFOAM framework, a numerical solver is developed to solve the coupled system of equations governing fluid flow, heat transfer, melting, and electrostatics. The numerical model considers the conjugate heat transfer in the electrodes and walls of the heat sink. The electric potential distribution in the heat sink walls is also considered. The induced electroconvective flow due to the applied electric field enhances flow velocity, alters flow structure, accelerates melting, and augments heat transfer. The heat dissipation mechanism in the EHD-assisted PCM heat sink is analyzed, and its thermal performance is evaluated in terms of heat dissipating capacity at varying applied voltages and orientations. The assistance of the EHD flow leads to a notable reduction in the total melting time. The heat sink exhibits equal performance irrespective of the orientation due to the presence of the electric field. Higher applied voltages result in higher heat dissipation capacity. A maximum of 61.45% increase in heat dissipating capacity is achieved for the parameter space considered herein. The increased heat dissipation capacity is almost ten times higher than the extra power required to generate the EHD flow.
EHD based vortex generation in microchannels
Flow and conjugate heat transfer in a microchannel in the presence of the electric-field-induced Onsager–Wien effect is investigated. A novel design is proposed to induce a pseudo- roughness effect in the microchannel and thereby increasing the heat transfer. A series of thin plate electrode pairs are flushed along the bottom wall of the microchannel. The electric-field-enhanced dissociation of ions induces the Onsager–Wien effect, and generates small flow vortices near the bottom wall of the channel. These flow vortices with sharp local velocity gradients effectively disrupt the viscous and thermal boundary layers, and thus, introduce a pseudo-roughness effect. This disruption of the boundary layers improves the heat transfer between the channel wall and the working fluid. The thermal and hydraulic performances in the microchannel are quantified as a function of the flow Reynolds number (Re) and electric Reynolds number (Re_EL). In general, the performance factor PF is higher when the flow and electric Reynolds numbers are higher. However, the associated pressure drop penalty reduces the PF (PF < 1) in viscous-effect-dominated flows at Re = 250. By contrast, the Onsager–Wien effect increases the PF to a maximum value of 1.26 in inertia-dominated flows at Re =1000 and Re_EL = 15. A significant heat transfer enhancement is realized, even at a low applied voltage of ~1 kV. The results of this study indicate that the pseudo-roughness produced by the electric-field-induced Onsager–Wien effect can substantially enhance the heat transfer in a microchannel with a trivial amount of additional power consumption.
