Faculty Publications
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Item Characterization of metal-PCMs for thermal energy storage applications(Trans Tech Publications Ltd ttp@transtec.ch, 2015) Sudheer, R.; Prabhu, K.In recent years phase change materials have emerged to be ideal energy storage materials for their higher energy density over sensible heat storing materials. Use of phase change materials (PCM) have been successfully implemented at lower temperature applications with various organic compounds. On the other hand, high temperature applications have been solely dominated by various salts, their eutectics and mixtures as phase change materials. This work discusses the suitability of metals and alloys for thermal energy storage applications as the phase change material. Metals offer superior thermal conductivities with considerable energy density compared to salts. Here, two alloys namely, Sn-0.3Ag-0.7Cu (SAC) solidifying over 212-224°C and ZA8 (Zn-8%Al) solidifying over 378-405°C have been studied. Thermal analysis of PCMs using Computer Aided Cooling Curve Analysis (CA-CCA) and DSC technique were performed to predict the solidification path. In addition to this, Newtonian technique was employed to estimate the latent heat of fusion for these phase change materials. Cooling rate curves and Fraction Solid curves offered a better insight into their ability to receive and discharge heat over the concerned temperature range. © (2015) Trans Tech Publications, Switzerland.Item Effect of Ce melt treatment on solidification path of ZA8 alloy(Institute of Physics Publishing michael.roberts@iop.org, 2016) Sudheer, R.; Vijayan, V.; Prabhu, K.The solidification path of ZA8 alloy with Ce addition was characterized using Newtonian technique of thermal analysis. The solidification events were determined using cooling curve and its first derivative curve. The microstructure and chemical composition of various phases in the alloy were studied using EDS, SEM and XRD techniques. It was found that the addition of Ce did not cause formation of new phases. However, it hinders the nucleation of stable β dendrites in the alloy. The presence of Ce promotes the eutectoid phase transformation and increases the hardness of the alloy. Latent heat of solidification and heat of eutectoid transformation were found to increase on Ce addition. The upward solidification of the alloy against Cu chill was analysed. Chilling had significant influence on solidification parameters, and caused refinement of the microstructure. The addition of Ce to the melt had no effect during chill casting of the alloy.Item A Computer Aided Cooling Curve Analysis method to study phase change materials for thermal energy storage applications(Elsevier Ltd, 2016) Sudheer, R.; Prabhu, K.N.The suitability of a simple Computer Aided Cooling Curve Analysis (CACCA) technique for characterizing thermal energy storage phase change materials (PCM) was proposed in the present work. Two modes of CACCA, namely, Newtonian and Fourier techniques were used to predict the phase transition temperatures, the latent heat of fusion and thermal diffusivities of PCMs. Solidification of potassium nitrate and zinc-8% aluminium alloy (ZA8) was studied using CACCA method. These PCMs were chosen to demonstrate the ability of the proposed technique to characterize PCMs freezing at a single temperature as well as over a range of temperatures. CACCA method showed that potassium nitrate and ZA8 are suitable candidate materials for TES applications operating at 300-350 °C and 350-450 °C respectively. © 2015 Elsevier Ltd.Item Cooling Curve Analysis of Micro- and Nanographite Particle-Embedded Salt-PCMs for Thermal Energy Storage Applications(Springer New York LLC barbara.b.bertram@gsk.com, 2017) Sudheer, R.; Prabhu, K.N.In recent years, the focus of phase change materials (PCM) research was on the development of salt mixtures with particle additives to improve their thermal energy storage (TES) functionalities. The effect of addition of microsized (50 ?m) and nanosized (400 nm) graphite particles on TES parameters of potassium nitrate was analyzed in this work. A novel technique of computer-aided cooling curve analysis was employed here to study the suitability of large inhomogeneous PCM samples. The addition of graphite micro- and nanoparticles reduced the solidification time of the PCM significantly enhancing the heat removal rates, in the first thermal cycle. The benefits of dispersing nanoparticles diminished in successive 10 thermal cycles, and its performance was comparable to the microparticle-embedded PCM thereafter. The decay of TES functionalities on thermal cycling is attributed to the agglomeration of nanoparticles which was observed in SEM images. The thermal diffusivity property of the PCM decreased with addition of graphite particles. With no considerable change in the cooling rates and a simultaneous decrease in thermal diffusivity, it is concluded that the addition of graphite particles increased the specific heat capacity of the PCM. It is also suggested that the additive concentration should not be greater than 0.1% by weight of the PCM sample. © 2017, ASM International.Item Assessment of PCM-container interfacial heat transfer using a hot/cold probe technique(John Wiley and Sons Inc. P.O.Box 18667 Newark NJ 07191-8667, 2019) Sudheer, R.; Prabhu, K.N.A novel technique for assessing heat transfer characteristics of salt-based phase change materials (PCM) was proposed here. The method is based on solution to inverse heat conduction problem. Nanoparticles (Graphite, Graphene, and multi wall carbon nanotube [MWCNT]) were dispersed in the PCM (KNO3) to assess their respective influence on heat transfer in the PCM. Graphite added PCM offered highest heat flow values and heating rates, while the pure salt-PCM offered the least. The probe material had a significant influence on the heat transfer rates at the PCM-probe interface. © 2018 Wiley Periodicals, Inc.