Papers by Keyword: Phase Change Materials (PCM)

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Authors: Zhi Mei Sun, Yuan Chun Pan, Bai Sheng Sa, Jian Zhou
Abstract: On the basis of ab initio total energy calculations, we have performed an extensive study on the stacking sequence and random occupation of Ge and Sb to make the same layer in stable hexagonal Ge2Sb2Te5 (h-GST), an excellent candidate for phase change random memory applications. The results demonstrate that the atomic arrangements have great effects on lattice parameter c and electronic properties of h-GST. h-GST changes from semiconductor to metallic behavior as varying the atomic sequence.
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Authors: Min Wu, Joe Dong, Andy Zhao, Wai Ching Tang, Willy Sher, Guang Wei Chen, Shuo Chen, Zhi Dan Qin, Yan Zhou, Yin Wang
Abstract: Construction workers are vulnerable to heat stress, and a number of heat-related injuries and deaths have been reported. This study thus introduces a phase change material (PCM) based cooling garment designed for construction workers. The PCM cooling garment will be effective in reducing the workers body temperature and can extend their maximum tolerable time on sites.
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Authors: Thomas Fiedler, Irina V. Belova, Andreas Öchsner, Graeme E. Murch
Abstract: Heat sinks enable the storage of energy that would otherwise be lost, thus ensuring significant energy-savings and fewer greenhouse gas emissions. Heat sinks also play the major role in the efficient temperature control of devices such as batteries. In principle, any material can act as a heat sink – traditionally, copper is used for many applications. However, copper is relatively expensive, has a high density and only a limited energy storage capacity. In contrast, a phase-change material (PCM) allows in effect an additional storage of energy through its phase change thus greatly increasing the achievable energy density. The aim of this work is the numerical analysis of the transient heat transfer in composite heat sinks containing phase-change materials. For the first time, a recently formulated Lattice Monte Carlo Method is applied to determine temperature distributions and the amount of energy transferred versus time in phase change materials.
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Authors: Yong Qi Xie, Peng Tao Chi, Jian Zu Yu, Jun Song
Abstract: The heat transfer enhancement in a latent heat energy storage device through embedment of copper foam (CF) is reported. The CF had a 96% porosity and the phase change material (PCM) was 25# paraffin. The CF and PCM were contained in a cuboid sample. A prototype test room was designed to numerically investigate the performance of the device. The melting and freezing process of the PCM and the day-night temperature of the room were observed. The results show that the tested totally melting time of the PCM is 8.72 hours during the daytime while the freezing time is 8.19 hours at night, and the phase change process could accomplish within 8-9 hours. The maximum temperature difference of the room is reduced 8.3°C. The room comfort could be significantly enhanced under the premise of less air conditioning energy consumption by applying the device.
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Authors: Chen Hao Wang, Meng Hao Chen, Jeng Der Huang, Chia Ray Chen
Abstract: A numerical study of the effectiveness of phase change material (PCM) used on FORMOSAT-7 at the preliminary design phase is presented in this study. N-eicosane is used as the PCM for its melting temperature. To compare the performance of PCM, different messes of PCM are applied for high-power-dissipating component with short-duty-cycle. The results show that PCM can improve the thermal stability of component by not only moderating peak temperature for worst hot case but also preventing sudden temperature decrease when the power mode of component changed. However, mass addition of PCM reduces the duration of the maximum temperature and the minimum temperature due to the better thermal conductivity of solid phase. Therefore, an optimization of mass is suggested for the application of PCM.
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Authors: Li Guang Xiao, Shuo Feng, Gang Liu, Shi Ting Zhang
Abstract: The thermal insulation mortar with cinders and phase change materials which is made from expanded perlites adsorbing composite phase change material, cinders and vitrified small ball as lightweight aggregate has the characteristics of both energy storage and thermal insulation. In this paper,we studied the effect of redispersible emulsion powder, methyl cellulose ether, organic fiber and water-reducing agent on the performance of thermal insulation mortar with cinders and phase change materials. The result showed that all the performance met the national standards of the thermal insulation mortar.
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Authors: Ho Dong Yang, Yool Kwon Oh
Abstract: This study focused on observing the melting phenomena and investigated a principle factor of enhanced heat transfer in phase change material when the ultrasonic vibrations were applied during the melting process. For visualization, particle image velocimetry and thermal-vision camera for observing the flow phenomenon was used. Also, experiments were performed to obtain the experimental results such as melting time and temperature distribution. Besides, structural vibration simulator which is applying a coupled finite element-boundary element method (Coupled FE-BEM) was used for calculation of acoustic pressure occurred by ultrasonic vibrations in liquid region. The results of experimental and numerical observations show that acoustic streaming induced by ultrasonic vibrations is one of the prime effects acoustically enhanced phase change heat transfer and help to accelerate the melting of phase change material. Also, the application technique of visualization and computational simulation introduced in this study is very useful and important to analyze the mechanical behavior of material in a fast fluid dynamic or acoustic field.
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Authors: Quan Ying Yan, Li Li Jin, Lin Zhang
Abstract: In this paper, the types, properties and selection of phase-change materials used in the wall were evaluated. The feasibility and methods to add phase change materials into the wall were discussed. The application and development situation of the phase change material wall in the practice were elaborated. Some problems to be solved are pointed out.
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Authors: Saad Ahmed, Mohamed Gadalla
Abstract: This research work investigates the heat transfer characteristics of a direct contact heat exchanger. A cold two phase refrigerant R134a is injected into water stored in an evaporator to exchange directly heat with the water and form clathrates during the charging mode of the operation. The clathrate is used later for obtaining chilled water for air-conditioning purposes. It was found that the performance of the system depends on the refrigerant, its ratio to water, compressor speed and the mass flow rate of the refrigerant.
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Authors: De Feng Ding, Jian Hong Chai, Li Feng Wang, Wu Chen
Abstract: An advanced experimental rig for heat pump water heaters was established. The performances of both a phase change heat-storage-type heat pump water heater (Type A) and a conventional heat pump water heater (Type B) were tested and compared according to GB/T 23137-2008 using the experimental rig. The results showed that the existence of phase transition temperature platform enabled the phase change heat-storage-type heat pump heater run longer and more steadily. When the same hot water heat capacity obtained, the volume of the accumulator in the Type A water heater accounted for about 56.9% of that of the water tank in the Type B water heater, which could save the overall size of water heater significantly and therefore promote the wide application of energy-saving heat pump water heaters.
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