BITS Faculty Publications
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Item Study on thermal storage properties of microencapsulated organic ester as phase change material for cooling application(Taylor & Francis, 2019-11) Parameshwaran, R.The phase change materials (PCMs) are latent thermal energy storage materials to store and release energy in the form of latent heat with a change in internal energy. The microencapsulation technique overcomes the limitations faced by the PCMs during energy storage and release. In this study, the new ester-based non-paraffin PCM was microencapsulated into an organic shell using in-situ polymerisation technique. The as-prepared MPCMs was characterised using the field emission electron microscope (FESEM), fourier transform Infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) techniques. The results show that the MPCM characterised using FESEM has exhibited a good morphology. The chemical stability studies carried using FTIR spectroscopy also confirmed the formation of microcapsules was only by physical interaction. The DSC test results also signify that microcapsules have a latent heat of enthalpy of 65.32 kJ/kg, with onset melting temperature of 8.57°C. Thus, this ensures the MPCM to be considered as a potential candidate for the CTES application.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 organic phase change material for waste heat recovery applications(Elsevier, 2018) Parameshwaran, R.The phase change materials (PCMs) are a class of materials which exhibit good phase transformations by undergoing cyclic freezing and melting processes through the influence of heat transfer. The increased research on materials has paved way for the development of heat storage materials with enhanced thermophysical properties suitable for waste heat recovery applications. Waste heat recovery is a practice that affords lower energy input through thermal energy exchange among sub-systems, whilecurbing pollution. This paper presents the experimental investigation on thermophysical properties and heat storage characteristics of an organic PCM for waste heat recovery applications. Experimental results reveal that, the organic PCM being utilized has exhibited congruent phase transition characteristics (∼60.8 °C), high latent heat capacity (∼164.28 kJ/kg), good thermal conductivity, and thermal stability as well. The test results suggest that, during the heating and cooling cycles, the rate at which the energy is being transferred between the PCM and the surrounding fluid strongly depends on the thermophysical properties and heat storage potential of the PCM. Heat transfer rates largely varied with the operating conditions, ranging from a few watts to over 1kW. These attributes enabled the PCM to be considered as a viable and energetic material for waste heat recovery applications.Item Microencapsulated bio-based phase change material-micro concrete composite for thermal energy storage(Elsevier, 2021-07) Parameshwaran, R.The quest and interest shown towards developing organic phase change materials (PCMs) for thermal energy storage (TES) applications in buildings are gaining momentum in recent years. From this perspective, the present study aims at developing a novel microencapsulated bio-based phase change material (MbP) integrated in to a micro concrete composite (MbPMC) for thermal energy storage in buildings. The MbP and MbPMC were experimentally characterized in terms of their morphological, thermal and structural properties. The surface morphology results signified that, the as-prepared MbP particles being formed were near-spherical in shape with sizes ranging between 2 μm and 10 μm. The highly crystalline nature of the bio-based PCM chains and the amorphous structure of the shell material were confirmed through the X-ray diffraction analysis. The Fourier transform infrared (FTIR) spectra has further confirmed the chemical stability between the core (PCM) and the shell material. The MbP has exhibited congruent phase change behavior with a good latent heat potential of 47.31 J/g. Besides, the MbP was found to be thermally stable, commencing from the operating temperature of 35 °C up to 150 °C, as confirmed through the leakage and thermogravimetric tests. A unique and optimized sequential operation of mixing the ingredients for preparing MbPMC matrix was established with a view to obtain the best end product. The as-prepared MbPMC has exhibited adequate structural integrity with a compressive strength of 38.78 MPa at a MbP dosage of 0.075% by the weight of cementitious materials added in the mix. Ultrasonic pulse velocities (UPV), along the directions orthogonal to the direction of pour of the concrete specimens, were observed to be very close, thus proving that the densities, across the cross section of the specimen are more or less uniform. For incremental dosages of MbP, the trend observed in the indicative compressive strengths of MbPMC specimens from rebound hammer tests was observed to be similar to the trend observed in the compressive strength values obtained from the compressive testing machine (CTM). In total, these test results have revealed the ability and stability of the MbP incorporated micro concrete composite (MbPMC) for achieving thermal energy storage and passive cooling in buildings without sacrificing its structural integrity.