Author ORCID Identifier
https://orcid.org/0000-0002-1371-7014
Biosketch
Doctoral researcher specializing in the intensification of latent heat thermal energy storage (TES) systems through additive incorporated phase change material (PCM) composites. My doctoral work centers on sodium nitrate (NaNO₃)-based composites engineered with metal oxide nanomaterials and carbon allotropes as additives to overcome the intrinsically low thermal conductivity and slow charge–discharge kinetics of molten-salt PCMs, with applications in concentrated solar power and industrial waste-heat recovery. Combines hands-on experimental synthesis and thermophysical characterization with rigorous heat-transfer modelling and statistical validation, and has authored twelve peer-reviewed publications across thermal energy storage, nanomaterials, and downstream bioprocessing.
Date of Award
10-8-2026
Document Type
Thesis
School
School of Chemical & Biotechnology
Programme
Ph.D.-Doctoral of Philosophy
First Advisor
Dr.K.S.Rajan
Keywords
Thermal Energy Storage, Phase Change Material, Latent Heat, Sodium Nitrate, Heat Transfer Coefficient
Abstract
Thermal energy storage (TES) systems employing phase change materials (PCM) bridge the gap between thermal energy demand and supply. The low thermal conductivity of sodium nitrate (NaNO3), an inorganic PCM for high-temperature TES systems restricts charging and discharging kinetics, reducing system-level performance. This thesis investigates the intensification of sodium nitrate-based thermal energy storage systems through the incorporation of different classes of additives. Metal oxides (zinc oxide and aluminium oxide) and carbon-based materials (graphene oxide (GO) and expanded graphite (EG)), were incorporated into NaNO3 to improve its thermophysical properties (thermal conductivity, latent heat, specific heat).
Composites were prepared using low-energy ball milling. At optimal concentrations, ZnO – NaNO3, Al2O3 – NaNO3 and GO – NaNO3 composites provided thermal conductivity enhancements (22.7%, 22.8% and 24.2% respectively), and specific heat capacity enhancements in both solid and liquid phases (17% and 43.5%; 18% and 46.5%; 15.8% and 16.8% respectively). For the EG – NaNO3 composite with 40 wt.% of EG, thermal conductivity was increased by 19 times, while the latent heat was reduced by 41%, both in comparison with that of NaNO3.
This work assessed the discharge kinetics of NaNO3 and NaNO3-based composites during the recovery of latent heat and solid-phase sensible heat using two different heat transfer fluids (well-mixed Therminol-55 and air under forced convection). The overall heat transfer coefficient and PCM-side heat transfer coefficient for thermal energy discharge from ZnO – NaNO3, Al2O3 – NaNO3, and EG – NaNO3 composites were higher than those from NaNO3. Notably, the 40 wt.% EG – NaNO3 composite reduced solidification time by 91% and achieved a six-fold increase in overall heat transfer coefficient for thermal energy discharge to Therminol-55. The mechanisms responsible for the modulations in thermophysical properties and discharge kinetics have been elucidated.
Selected compositions of these composites exhibited excellent cyclic stability, retaining their phase change characteristics after 500 thermal cycles. The synergy of utilizing metal oxide nanoparticles and expanded graphite for augmentation of thermal conductivity, total energy capacity and discharge kinetics has also been explored. The composites reported in this work, with their enhanced energy storage capacity and improved discharge kinetics, are well suited for use in solar thermal energy storage systems.
Recommended Citation
V, Hari Suthan Mr, "Intensification of Thermal Energy Storage Systems based on Sodium Nitrate" (2026). Theses and Dissertations. 221.
https://knowledgeconnect.sastra.edu/theses/221