Department of Mechanical engineering
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Item Dimethyl Adipate-Based Microencapsulated Phase Change Material with Silica Shell for Cool Thermal Energy Storage(Springer, 2020-11) Parameshwaran, R.Phase change materials (PCM) have the ability to store and release thermal energy. Encapsulation of these energy storage materials overcomes the difficulties that can enable them for a broad range of applications. In the present study, microencapsulation of dimethyl adipate into silica shell was carried through interfacial hydrolysis and polycondensation method. The prepared microencapsulated phase change materials (MPCM) were characterised using a field emission scanning electron microscope, have shown good sphericity with an average particle size of 596 nm. The chemical structure of MPCM obtained using Fourier transform infrared spectroscopy has exhibited good chemical stability between shell and core materials. Latent heat of enthalpy measured using differential scanning calorimetry was around 24 kJ/kg with onset melting and end set melting as 7.33 °C and 11.97 °C, respectively. Furthermore, thermo-gravimetric analysis studies have shown that MPCM exhibited end set temperatures as 180 °C. Due to the inorganic shell coating over the PCM droplets, MPCM has shown an increase in thermal stability. These properties make MPCM as a viable candidate for cool thermal energy storage applications.Item Experimental Study on PCM-Based External Wall Cladding for Energy Efficient Buildings(Springer, 2020-01) Parameshwaran, R.The present work reports the experimental investigation of the phase change material (PCM) incorporated into the external wall claddings for achieving energy conservation in building through a passive cooling application. Three types of wall claddings of size 458 mm × 458 mm (1.5 ft × 1.5 ft) in dimension were developed in this experimental study. Lauric acid was utilized as the PCM to be incorporated into the wall claddings. Experimental results suggest that the lauric acid exhibited good latent heat potential, congruent phase change processes, and was thermally stable within operating temperature ranges. Furthermore, it was concluded that out of three cladding types being tested, the percentage drop of air temperature was more in composite wall cladding and the percentage drop of heat flux was more in aluminum box cladding with PCM and coarse aggregate. In total, the cladding incorporated with the PCM was found to be the potential candidate for the enhancement of energy efficiency in building through passive thermal storage and cooling load reduction.Item Preparation, thermal and structural properties of n-octadecane/melamine formaldehyde nanocapsules embedded cement mortar for energy storage application in buildings(Elsevier, 2022) Parameshwaran, R.Phase change materials (PCM) integrated into building fabrics plays an important role in achieving energy efficiency in buildings through thermal energy storage. The incorporation of nanotechnology-based heat storage materials into building fabric materials are becoming increasingly popular in recent times. From this perspective, a novel nanoencapsulated PCM (NePCM) embedded cement mortar was developed and its thermal energy storage and structural properties were investigated, experimentally. In-situ polymerization technique was used to prepare the nanocapsule containing n-Octadecane as the PCM and melamine formaldehyde as the shell material. The particle size analysis results reveal that the size of NePCM ranged from 76 nm to 530 nm. The NePCM resulted in an appreciable encapsulation efficiency of 60.14 % with a melting temperature and latent heat of fusion of 26.01 °C and 122.24 kJ/kg, respectively. The NePCM exhibited good chemical and thermal stability. The pure PCM and the NePCM were embedded into cement mortar with varying proportions for the preparation of cube specimens and based on which a comparative study was performed. During curing the cube specimens for 28 days, leakage of the pure PCM from the cement mortar was noticed to some extent. On the other hand, no leakage issues were found in the NePCM embedded cement mortar, as a result of the shell material which protected the PCM from leaking. The PCM and NePCM embedded cement mortar cube specimens exhibited an excellent compressive strength of 56.8 MPa and 48.16 MPa, respectively. However, by increasing to 6 wt% of PCM content in cement mortar, the cube samples of PCM embedded cement mortar compressive strength was reduced to 44.41 %. Thus, the developed NePCM with improved thermal and structural properties can achieve enhanced energy storage and passive cooling in buildings without sacrificing the structural stability.Item Bio-based hexadecanol impregnated fly-ash aggregate as novel shape stabilized phase change material for solar thermal energy storage(Elsevier, 2022) Parameshwaran, R.In light of a variety of latent heat storage materials being available, the concept of utilization of organic PCMs for solar thermal energy storage (STES) is becoming increasingly attractive during the recent past. From this perspective, the present study is aimed at developing a new bio-based shape stabilized phase change material (BSPCM) for achieving passive cooling in buildings through STES. An eco-friendly BSPCM composite, consisting of the hexadecanol as the PCM and the modified porous fly ash-based pebbles as the supporting matrix, was prepared using the vacuum impregnation technique. The prepared BSPCM was then characterized thoroughly with respect to its morphology, crystal and surface structures, phase change properties, thermal stability, leakage stability, thermal conductivity and thermal reliability.Item Bio-based phase-change materials(Elsevier, 2020) Parameshwaran, R.The development and subsequent incorporation of the advanced materials and technologies in buildings, with a view to target energy savings, and to fulfill the energy requirements have been gaining impetus during the recent years. The inherent vision lying behind the state-of-the-art technological advancements taking place in the construction sector is to sustain the energy efficiency in both existing and newly developed buildings on a long run. Thermal energy storage (TES), achieved through the phase-change materials (PCMs), is one among a few energy-efficient technologies available. The energy demand at the end-user side can be greatly satisfied using the TES technologies. Using bio-based PCMs in buildings is considered to be an ever-growing as well as an emerging field of interest to wider scientific and engineering communities, worldwide. This chapter is devoted to provide an in-depth understanding of a variety of bio-based PCMs for accomplishing thermal storage and energy efficiency in buildings. The nucleus of this chapter is focused on the TES properties enhancement for a variety of bio-based PCMs through the incorporation of different functional materials thereby; energy efficiency in buildings can be achieved.Item Micro/nanoencapsulation of dimethyl adipate with melamine formaldehyde shell as phase change material slurries for cool thermal energy storage(Elsevier, 2022-06) Parameshwaran, R.The present study reports the encapsulation of dimethyl adipate into a polymer shell using in-situ polymerisation. Surface morphology, crystal structure, chemical stability, and thermal properties are characterised using various analytical methods and experimentally investigated. The surface morphology has shown excellent sphericity with a mean particle diameter of 900 nm. The measured enthalpy was 80.2 J/g, with the onset and peak melting temperatures are 6.4 °C and 9.6 °C, respectively. The calculated specific heat capacities of encapsulated dimethyl adipate are around 1.7 J/g.K and 2.3 J/g.K for solid and liquid states, respectively. Furthermore, thermal cycling performance was obtained as 95.3% after 100 thermal cycles. These capsules dispersed into the base fluid (deionized double distilled water) in appropriate proportions for the preparation of micro/nanoencapsulated phase change material slurries (MNPCMS). The prepared slurries have shown a marginal increase in viscosity compared to the base fluid. Therefore, the test results signified that the prepared MNPCMS can be considered as a potential candidate for cool thermal energy storage applications.Item Microcapsules of n-dodecanoic acid/melamine-formaldehyde with enhanced thermal energy storage capability for solar applications(Elsevier, 2022-09) Parameshwaran, R.A new bio-based microencapsulated phase change material (MEPCM) was synthesised by an in situ polymerisation method, and its thermal energy storage properties were experimentally studied. Bio-based n-dodecanoic acid with a high heat storage capacity was encapsulated by a melamine-formaldehyde (MF) polymeric shell. The MEPCM was characterised using field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and thermal conductivity analysis (TCA). The microcapsules had a perfectly spherical morphology with a core–shell microstructure. The MEPCM was chemically stable, and its crystallinity was unaltered. Dodecanoic acid encapsulated by the MF shell exhibited a high thermal energy storage capability of 99.3% and was observed to melt at 41.8 °C with a decent enthalpy of 41.7 kJ/kg. The prepared microcapsules were thermally stable up to 165.02 °C, which were also observed to be leak-proof well above the phase transition temperature. Furthermore, the thermal reliability of the MEPCM was good after 1000 thermal cycles. Overall, the MEPCM was a viable candidate for medium-temperature thermal energy storage applications.Item Cryogenic conditioning of microencapsulated phase change material for thermal energy storage(Springer, 2020-10) Parameshwaran, R.Microencapsulation is a viable technique to protect and retain the properties of phase change materials (PCMs) that are used in thermal energy storage (TES) applications. In this study, an organic ester as a phase change material was microencapsulated using melamine–formaldehyde as the shell material. This microencapsulated PCM (MPCM) was examined with cyclic cryogenic treatment and combined cyclic cryogenic heat treatment processes. The surface morphology studies showed that the shell surfaces had no distortions or roughness after cryogenic treatment. The cryogenically conditioned microcapsules exhibited diffraction peak intensity shifts and crystal structure changes. The onset of melting for the nonconditioned and conditioned microcapsules were measured to be 8.56–9.56 °C, respectively. Furthermore, after undergoing the cryogenic and heat treatment processes, the PCM microcapsules had appreciable latent heat capacities of 39.8 kJ/kg and 60.7 kJ/kg, respectively. Additionally, the microcapsules were found to have good chemical stability after the cryogenic treatment. In addition, the cryogenically conditioned microcapsules were found to be thermally stable up to 128.9 °C, whereas the nonconditioned microcapsules were stable up to 101.9 °C. Based on the test results, it is obvious that the cryogenically conditioned microcapsules exhibited good thermal properties and are very desirable for cool thermal energy storage applicationsItem Study on thermal energy storage properties of bio-based n-dodecanoic acid/fly ash as a novel shape-stabilized phase change material(Elsevier, 2022-02) Parameshwaran, R.In the present study, a novel BSPCM was prepared with the n-dodecanoic acid (or) LA phase change material, which was vacuum impregnated into the porous FA pebbles. The surface morphology of the BSPCM has confirmed the presence of the lauric acid in the porous supporting matrix. The XRD analysis of the BSPCM revealed that the crystalline nature of the PCM was unaltered after impregnation. The surface structure study verified the chemical compatibility between the PCM and supporting material. The DSC results showed that, BSPCM has exhibited a good latent heat of fusion of 68.93 kJ/kg with high thermal energy storage capability of 97.62%. The BSPCM was thermally stable up to 150 °C and showed good leakage stability up to 85 °C. Thermal reliability of the BSPCM performed for 1000 thermal cycles revealed excellent thermal reliability index of 96.76%. Further, thermal conductivity of BSPCM was found to be 0.1702 W/mK, which was attributed to the effective impregnation of the PCM into the fly ash pebbles. In total, the developed BSPCM can be a viable candidate for achieving passive thermal energy storage in buildings.Item Molten salts: Potential candidates for thermal energy storage applications(Wiley, 2022-07) Parameshwaran, R.Molten salts as thermal energy storage (TES) materials are gaining the attention of researchers worldwide due to their attributes like low vapor pressure, non-toxic nature, low cost and flexibility, high thermal stability, wide range of applications etc. This review presents potential applications of molten salts in solar and nuclear TES and the factors influencing their performance. Ternary salts (Hitec salt, Hitec XL) are found to be best suited for concentrated solar plants due to their lower melting point and higher efficiency. Two-tank direct energy storage system is found to be more economical due to the inexpensive salts (KCl-MgCl2), while thermoclines are found to be more thermally efficient due to the power cycles involved and the high volumetric heat capacity of the salts involved (LiF-NaF-KF). Heat storage density has been given special focus in this review and methods to increase the same in terms of salt composition changes are discussed in the paper. Methods of concatenating energy storage systems with nuclear power plants are also discussed with different types of nuclear reactors like MHTGR, PAHTR, VHTR, etc. Nanomodifications of molten salts are done to improve heat transfer properties and efficiency of the transfer. The best dopants for such modifications were found to be TiO2, SiO2, MWCNTs, etc. Future challenges for large scale deployment of molten salts viz., high volume expansion ratio, low thermal conductivity, incongruent melting, corrosion, etc., are listed and discussed. Corrosion of molten salts and its mitigation has been discussed in detail for developing next-generation storage systems and its remedies are also discussed.