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Solid–Liquid Phase Change Materials for Energy Storage
Published in Moghtada Mobedi, Kamel Hooman, Wen-Quan Tao, Solid–Liquid Thermal Energy Storage, 2022
A. Stamatiou, S. Maranda, L. J. Fischer, J. Worlitschek
Salt hydrates consist of inorganic salts (AB; A: Anion, B: Cation) and water (H2O). They form a crystalline solid phase with a general formula of AB·nH2O, where n has values of, e.g., 3 (trihydrate), 4 (tetrahydrate), and 10 (decahydrate). Phase change in salt hydrates is a process of dehydration and dissolving of the salt in the released water in case of melting and hydration in case of freezing; both processes with strong interaction of heat and mass transfer. Salt hydrates can be grouped according to their phase equilibrium behavior into congruent melting, semi-congruent-melting and incongruent-melting materials. In a congruent melting system, the solid and the liquid phases at the melting point consist of the same compositions. A semi-congruent material typically produces lower hydrated salts along with the hydrated salt with a composition corresponding to that of the original salt solution. Incongruent-melting materials are similar to semi-congruent materials but instead of the presence of lower hydrates in the solution anhydrous solid particles are produced while melting.
Thermodynamic Aspects of Phase Stability
Published in Mary Anne White, Physical Properties of Materials, 2018
The K–Na phase diagram shows that the composition at 54.0 mass% Na (which corresponds to KNa2) begins to melt at 7 °C, giving solid solution rich in Na, designated (Na), and a liquid depleted in Na relative to KNa2. As the temperature is increased, the proportion of liquid (which contains K and Na) and solid (Na-rich solid solution) changes, yielding more liquid as the temperature goes up. This liquid also becomes richer in Na as the temperature is increased, because it is forming from (Na). Eventually all the solid will become liquid. A major distinguishing feature between congruent and incongruent melting is that for congruent melting the vertical line at the compound composition directly reaches the liquid region; for incongruent melting, the vertical line at the compound composition stops short of the liquid region, usually at a horizontal line in the phase diagram.
Phase-Change Materials
Published in George A. Lane, Solar Heat Storage: Latent Heat Materials, 1986
For the purposes of discussion, the salt hydrates have been grouped according to their phase equilibrium behavior. First the well-behaved materials, congruent-melting, quasi-congruent-melting, congruent-melting isomorphous, and eutectic materials, are discussed. Finally the difficult semicongruent melting and incongruent-melting PCMs are presented. The various classes of phase equilibrium behavior are thoroughly discussed in Volume I, Chapter 3, Phase Equilibria, of this series. Calcium chloride hexahydrate, which per se should be listed under the semicongruent melting category, also has been placed in the congruent-melting group, because the most widely available commercial PCM contains phase equilibrium modifiers which prevent formation of hydrates other than the hexahydrate. Magnesium chloride hexahydrate, which is semicongruent melting, has been listed as “quasi-congruent” melting, since segregation to other hydrate phases is not observed in the laboratory or field.
Piezoelectric property optimization for piezoelectric single crystals using parametric estimation
Published in Journal of Asian Ceramic Societies, 2023
Ho-Yong Shin, Ho-Yong Lee, Il-Gok Hong, Jong-Ho Kim, Jong-in Im
There are two typical methods for manufacturing piezoelectric single crystals, the Bridgman and SSCG methods. The Bridgman method is useful for the synthesis of piezoelectric single crystals as it grows single crystals directly from the melt, which is a simple and cost effective method. However, this method has a disadvantage in that it is difficult to apply to high melting point or volatile components. The SSCG method has been considered as an alternative approach to solve the Bridgman method problem, as it does not require complete melting of the major components. Thus, the SSCG method is useful for the single crystal growth of materials with high melting temperatures, volatile components, and incongruent melting [25]. There are several types of piezoelectric single crystals which are categorized by their properties and components. The PMN-PT and PZN-PT single crystals with a low phase transition temperature and coercive electric field are classified as first generation piezoelectric single crystals, whereas those with an improved phase transition temperature and coercive electric field are classified as second-generation piezoelectric single crystals, such as PIN-PMN-PT and PMN-PZT. In addition, a single crystal is classified as third-generation if its piezoelectric properties are optimized according to a specific purpose by adding a donor or acceptor to the second-generation piezoelectric single crystal [26].
Heat Transfer Enhancement of Latent Heat Storage Using Novel Quadruple Helical Fins
Published in Heat Transfer Engineering, 2022
Athimoolam Sundaramahalingam, Selvaraj Jegadheeswaran
Over the last century, the global energy consumption has increased rapidly, propelled by a rising population and prosperity. Demand has grown for almost every outlet—coal, petroleum, gas, nuclear, wind, solar, etc. At the same time, the increasing use of fossil fuels is the leading cause for worldwide climate change. In order to overcome these challenges, a sustainable energy transition is crucial for the global energy system, replacing greenhouse gas resources with cleaner sources of energy [1]. Nevertheless, significant efforts to alleviate the energy demand are being made globally through the development of new power generation and storage technologies. Thus, scientists and researchers in the energy sector have turned into renewable energy forms and energy storage methods. In particular, solar thermal energy is shown to be highly promising for heating and cooling applications. However, solar thermal devices demand energy storage unit for uninterrupted operation. Latent heat thermal energy storage system (LHTESS) extends some advantages like high storage capacity, compactness, constant temperature operation and chemical stability. Nevertheless, LHTESS have practical limitations as most of the phase change materials (PCMs) which are storage mediums suffer from some or all problems such as below-par thermal conductivity, segregation of phase, incongruent melting and subcooling. Researchers have investigated a wide range of PCMs which include paraffins [2, 3], non-paraffins [4], salt hydrates [5], molten salts [6, 7], and eutectics [8, 9].
Molten-salt assisted synthesis and characterization of Mg2B2O5 and Al18B4O33 whiskers
Published in Journal of Asian Ceramic Societies, 2021
Zhaoyang Liu, Jingkun Yu, Xiangnan Wang, Xue Zhang, Jiakang Wang, Danbin Jia, Tianpeng Wen, Zhengguo Yan, Lei Yuan, Beiyue Ma
(Figure 14) shows the TG and DSC curves of the mixtures for preparing aluminum borate whiskers across a 50–1100°C range. The TG analysis indicates that a continuous weight loss occurs across the whole temperature range. The weight loss from 50°C to about 400°C can be associated with the decomposition of H3BO3 and thermal dehydration of KAl(SO4)2 · 12H2O, corresponding to the three endothermic peaks at about 80°C, 130°C, and 280°C on the DSC curve. The weight loss observed between 600°C and 1100°C is attributable to the thermal decomposition of KAl(SO4)2, leading to the formation of K2SO4, Al2O3 and SO3. This weight loss corresponds to the endothermic peak at about 595°C. At the same time, the endothermic peaks at about 440°C and 670°C are attributable to the melting of B2O3 and K2SO4 with the KCl salt, respectively. The endothermic peak found at about 950°C suggests the incongruent melting of Al4B2O9 into Al18B4O33 and a B2O3-rich liquid (Eq. 4), which is consistent with the XRD results regarding the transformation of the aluminum borate phase (Figure 13).