Browsing by Author "Chang, Chun-Che"

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Thermal hysteresis in phase-change materials: Encapsulated metal alloy core-shell microparticles
(2018-09-01)
Hsu, Ting-Heng
;
Chung, Chieh-Hsuan
;
Chung, Feng-Ju
;
Chang, Chun-Che
;
Lu, Ming-Chang
Thermal hysteresis (TH) is defined as the temperature difference between the melting points and crystallization temperatures of phase-change materials (PCMs). The magnitude of the TH is proportional to the energy loss in a system. In addition, the latent heats of the PCMs cannot be exploited if the TH is beyond the operation temperature range of a system. In this study, Zn/TiO2, Zn/Al2O3, and Zn/SiO2 core-shell microparticles were synthesized and the TH values of the microparticles were examined. The TH for the microparticles was mainly affected by the ramping rate in differential scanning calorimetry, the shell thermal resistance and the required temperature for heterogeneous nucleation. Given that Al2O3 possesses a superior thermal conductivity than that of TiO2 and SiO2, the Zn/Al2O3 core-shell microparticles provided the smallest TH among the three types of microparticles. The heat capacity of the salt can be enhanced by 6.7% by doping with 10 wt% Zn/Al2O3 microparticles while the viscosity increased from 1.3 to 3 cp. The study provided guidelines to modulate the TH of PCMs, and the concept learned from this study can be applied to enhancing the thermal energy storage in various thermal systems.
Tunable endothermic plateau for enhancing thermal energy storage obtained using binary metal alloy particles
(2016-07)
Lai, Chih-Chung
;
Lin, Shih-Ming
;
Chu, Yuan-Da
;
Chang, Chun-Che
;
Chueh, Yu-Lun
Thermal energy storage is crucial for various industrial systems. Enhancements in energy storage induced by latent heat have been demonstrated by using phase-change materials. However, these enhancements occur only at the melting points of the materials. In this study, we demonstrated the controllability of latent heat absorption/release in a certain temperature range. A wide endothermic plateau from 370 to 407 degrees C for the Hitec salt was obtained by releasing the latent heat of alloy particles embedded in the salt. The alloy particle-doped salt was applied to a Stirling engine to demonstrate its effectiveness in enhancing the energy and power outputs of the engine. Compared to pure salt, the alloy particle-doped salt can enhance the engine\'s energy output by 21%. With the advantages of scalable synthesis and superior thermal properties, the alloy particles have potential applications in energy storage enhancement in various thermal energy systems. (C) 2016 Published by Elsevier Ltd.