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Yudong Liu - One of the best experts on this subject based on the ideXlab platform.
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study on the Supercooling degree and nucleation behavior of water based graphene oxide nanofluids pcm
International Journal of Refrigeration-revue Internationale Du Froid, 2015Co-Authors: Yudong LiuAbstract:Abstract This article aimed to study the Supercooling degree and nucleation behavior of nanofluids phase change material. The nanofluids were prepared by adding small fraction of graphene oxide nanosheets in deionized water without any dispersants. The Supercooling degree of nanofluids with different concentrations was tested experimentally. The results show that the Supercooling degree can be reduced by 69.1%, and the nucleation was started in advance, shorting the time by 90.7%. Theoretical analysis based on the heterogeneous nucleation theory indicates that ice crystal nucleus cannot grow on the thickness surface of the graphene oxide nanosheet, while it can grow on the top or bottom surface of the nanosheet only when the Supercooling degree ΔT and the nanosheets size D meet the formula D ⋅ ΔT ≥4.2×10 −8 . Our study implies that graphene oxide nanofluids have the potential to be used as PCMs in cold storage applications because of their low Supercooling degree and rapid nucleation behavior.
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the effects of graphene oxide nanosheets and ultrasonic oscillation on the Supercooling and nucleation behavior of nanofluids pcms
Microfluidics and Nanofluidics, 2015Co-Authors: Yudong Liu, Yumin Liu, Runnan Gao, Quangui Peng, Liuzhu WeiAbstract:Nanofluids phase change materials (PCMs) have attracted extensive attention in cold storage applications recently. This paper presents a latest experimental research about the effects of graphene oxide nanosheets and ultrasonic oscillation on the nucleation behavior and Supercooling degree of nanofluids PCMs. The results demonstrate that the Supercooling degree of nanofluids is suppressed considerably, and the maximum reduction of Supercooling degree was 69.1 %; the nucleation started by 90.7 % time in advance, which indicates that nucleation is easier to achieve in nanofluids because of the heterogeneous nucleation aroused by graphene oxide nanosheets. On the other hand, it is observed that ultrasound oscillation also makes a great contribution to reducing the nucleation time and Supercooling degree, and the Supercooling degree is almost zero in graphene oxide nanofluids under ultrasound radiation. It is believed that graphene oxide nanofluids will be the excellent candidates for the cold storage materials because of their lower Supercooling degrees and shorter nucleation time.
Liu Yudong - One of the best experts on this subject based on the ideXlab platform.
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Supercooling and heterogeneous nucleation in acoustically levitated deionized water and graphene oxide nanofluids droplets
Experimental Thermal and Fluid Science, 2019Co-Authors: Fu Jing, Geng Shichao, Gao Yongkun, Liu Yixin, Miao Pengjv, Chen Bing, Tan Junkun, Liu YudongAbstract:Abstract The Supercooling and heterogeneous nucleation factors of deionized water and graphene oxide nanofluid were investigated in this study. Graphene oxide nanofluid (0.03 wt%) was prepared by adding graphene oxide nanosheets into deionized water. A large number of nucleation experiments have been performed to quantify the Supercooling degree of acoustically levitated deionized water and graphene oxide nanofluid droplets. These deionized water droplets were supercooled at 2.5–15.6 K, whereas the Supercooling degrees of graphene oxide nanofluid droplets varied from 2.6 K to 12.5 K. In addition, the heterogeneous nucleation was investigated by the statistical analysis based on the classical nucleation theory. Results demonstrated that the heterogeneous nucleation factor for graphene oxide nanofluid was less than that of deionized water, and the nucleation area for graphene oxide nanofluid was 4.44 times that of deionized water. Consequently, the nucleation rate of the graphene oxide nanofluid was increased and the Supercooling degree was reduced.
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nucleation rate and Supercooling degree of water based graphene oxide nanofluids
Applied Thermal Engineering, 2017Co-Authors: Liu Yudong, Wang Jiangqing, Su Chuangjian, Geng Shichao, Gao Yongkun, Peng QuanguiAbstract:Abstract Graphene oxide nanosheet is considered as an excellent additive owing to desirable thermal conductivity and hydrophilicity. Graphene oxide nanofluids were prepared by adding graphene oxide nanosheets into deionized water under ultrasonic oscillation. Particle size distributions were measured by Laser Size and Zeta Potential Analyzer. Nucleation rates and Supercooling degrees of deionized water and graphene oxide nanofluids are investigated using classical nucleation theory. Deionized water nucleates homogeneously, but graphene oxide nanofluids involve homogeneous nucleation of inside deionized water and heterogeneous nucleation arising from graphene oxide nanosheets. Our theoretical analysis shows that two types of nucleation in graphene oxide nanofluids can differ by 23.08 orders of magnitude at 241.65 K. Therefore, nucleation rate mainly refers to the heterogeneous part. The heterogeneous nucleation rates are obtained by integrating the particle size based on the probability density functions and particle size distributions fitted via MATLAB. The Supercooling degree of deionized water is approximately 31.5 K, whereas the Supercooling degrees of four different concentrations of graphene oxide nanofluids are 7.98, 7.93, 3.05, and 3.03 K. The Supercooling degrees were reduced by more than 74% with the corresponding increase in volume concentration. Therefore, graphene oxide nanofluids can be used as alternative phase change materials in cold storage application because of their low Supercooling degrees.
Peng Quangui - One of the best experts on this subject based on the ideXlab platform.
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nucleation rate and Supercooling degree of water based graphene oxide nanofluids
Applied Thermal Engineering, 2017Co-Authors: Liu Yudong, Wang Jiangqing, Su Chuangjian, Geng Shichao, Gao Yongkun, Peng QuanguiAbstract:Abstract Graphene oxide nanosheet is considered as an excellent additive owing to desirable thermal conductivity and hydrophilicity. Graphene oxide nanofluids were prepared by adding graphene oxide nanosheets into deionized water under ultrasonic oscillation. Particle size distributions were measured by Laser Size and Zeta Potential Analyzer. Nucleation rates and Supercooling degrees of deionized water and graphene oxide nanofluids are investigated using classical nucleation theory. Deionized water nucleates homogeneously, but graphene oxide nanofluids involve homogeneous nucleation of inside deionized water and heterogeneous nucleation arising from graphene oxide nanosheets. Our theoretical analysis shows that two types of nucleation in graphene oxide nanofluids can differ by 23.08 orders of magnitude at 241.65 K. Therefore, nucleation rate mainly refers to the heterogeneous part. The heterogeneous nucleation rates are obtained by integrating the particle size based on the probability density functions and particle size distributions fitted via MATLAB. The Supercooling degree of deionized water is approximately 31.5 K, whereas the Supercooling degrees of four different concentrations of graphene oxide nanofluids are 7.98, 7.93, 3.05, and 3.03 K. The Supercooling degrees were reduced by more than 74% with the corresponding increase in volume concentration. Therefore, graphene oxide nanofluids can be used as alternative phase change materials in cold storage application because of their low Supercooling degrees.
Xiaojiao Yang - One of the best experts on this subject based on the ideXlab platform.
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experimental studies on the Supercooling and melting freezing characteristics of nano copper sodium acetate trihydrate composite phase change materials
Renewable Energy, 2016Co-Authors: Wenlong Cui, Yanping Yuan, Liangliang Sun, Xiaoling Cao, Xiaojiao YangAbstract:This paper reports that Nano-copper (Nano-Cu), which possesses high thermal and electrical conductivity, as an additive, can improve the Supercooling properties of sodium acetate trihydrate (CH3COONa·3H2O, SAT) and enhance its thermal conductivity. To investigate the effect of Nano-Cu content on the degree of Supercooling of SAT, composite phase change materials containing SAT, Nano-Cu (0.4%, 0.5%, 0.6%, 0.7% and 0.8%), CMC (thickening agent) and sodium dodecyl sulfonate (C12H25NaO3S, dispersant) were prepared. Melting-freezing experiments involving the composite materials indicated that the rate of heat transfer increased by nearly 20%. When an optimal amount of Nano-Cu (i.e., 0.5%) was added to SAT, the degree of Supercooling was reduced to approximately 0.5 °C. Compared to the use of inorganic salt hydrates as nucleating agents, Nano-Cu is significantly advantageous in reducing the degree of Supercooling of SAT. The maximum improvement in Supercooling was observed when the melting-freezing experiment was conducted at an initial temperature of 70 °C. The thermal conductivity of the reported composite phasechange materialsis approximately 20% higher than that of pure SAT.
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Experimental studies on the Supercooling and melting/freezing characteristics of nano-copper/sodium acetate trihydrate composite phase change materials
Renewable Energy, 2016Co-Authors: Wenlong Cui, Yanping Yuan, Liangliang Sun, Xiaoling Cao, Xiaojiao YangAbstract:This paper reports that Nano-copper (Nano-Cu), which possesses high thermal and electrical conductivity, as an additive, can improve the Supercooling properties of sodium acetate trihydrate (CH3COONa·3H2O, SAT) and enhance its thermal conductivity. To investigate the effect of Nano-Cu content on the degree of Supercooling of SAT, composite phase change materials containing SAT, Nano-Cu (0.4%, 0.5%, 0.6%, 0.7% and 0.8%), CMC (thickening agent) and sodium dodecyl sulfonate (C12H25NaO3S, dispersant) were prepared. Melting-freezing experiments involving the composite materials indicated that the rate of heat transfer increased by nearly 20%. When an optimal amount of Nano-Cu (i.e., 0.5%) was added to SAT, the degree of Supercooling was reduced to approximately 0.5 °C. Compared to the use of inorganic salt hydrates as nucleating agents, Nano-Cu is significantly advantageous in reducing the degree of Supercooling of SAT. The maximum improvement in Supercooling was observed when the melting-freezing experiment was conducted at an initial temperature of 70 °C. The thermal conductivity of the reported composite phasechange materialsis approximately 20% higher than that of pure SAT.
R. Abbaschian - One of the best experts on this subject based on the ideXlab platform.
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Microstructure and phase selection in supercooled copper alloys exhibiting metastable liquid miscibility gaps
Journal of Materials Science, 2012Co-Authors: A. Munitz, A. Venkert, P. Landau, M. J. Kaufman, R. AbbaschianAbstract:The influence of both bulk Supercooling and cooling rate on the microstructure and phase selection during solidification of Cu–Co, Cu–Co–Fe, and Cu–Nb alloys exhibiting metastable liquid miscibility gaps were investigated using scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. Containerless electromagnetic levitation was used to achieve large bulk Supercoolings in the specimens. Supercooling of these alloys below a certain temperature resulted in metastable separation of the melt into two liquids, a Cu-lean (Co, Co + Fe, or Nb enriched) melt (L1) and a Cu-rich melt (L2). Usually, the microstructure of the phase-separated alloys consisted of spherulites corresponding to one of the phase-separated liquids embedded in a matrix corresponding to the other. The microstructure and phase selection are found to depend on factors such as: alloy composition, Supercooling level, whether the material was dropped before or after recalescence, and the cooling rate during solidification. The following results were observed: (1) solidification of metastable ε-Cu with enhanced Co (or Co + Fe, or Nb) solubility; (2) partitionless solidification of the L1 and L2 liquids; (3) spinodal decomposition of the supercooled liquid, and (4) secondary melt separation. The results are discussed and related to current solidification theories regarding solidification paths for the different conditions examined. The miscibility gap boundaries for the different alloys were determined and compared with those reported in the literature.
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microstructure and phase selection in supercooled copper alloys exhibiting metastable liquid miscibility gaps
Journal of Materials Science, 2012Co-Authors: A. Munitz, A. Venkert, P. Landau, M. J. Kaufman, R. AbbaschianAbstract:The influence of both bulk Supercooling and cooling rate on the microstructure and phase selection during solidification of Cu–Co, Cu–Co–Fe, and Cu–Nb alloys exhibiting metastable liquid miscibility gaps were investigated using scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. Containerless electromagnetic levitation was used to achieve large bulk Supercoolings in the specimens. Supercooling of these alloys below a certain temperature resulted in metastable separation of the melt into two liquids, a Cu-lean (Co, Co + Fe, or Nb enriched) melt (L1) and a Cu-rich melt (L2). Usually, the microstructure of the phase-separated alloys consisted of spherulites corresponding to one of the phase-separated liquids embedded in a matrix corresponding to the other. The microstructure and phase selection are found to depend on factors such as: alloy composition, Supercooling level, whether the material was dropped before or after recalescence, and the cooling rate during solidification. The following results were observed: (1) solidification of metastable e-Cu with enhanced Co (or Co + Fe, or Nb) solubility; (2) partitionless solidification of the L1 and L2 liquids; (3) spinodal decomposition of the supercooled liquid, and (4) secondary melt separation. The results are discussed and related to current solidification theories regarding solidification paths for the different conditions examined. The miscibility gap boundaries for the different alloys were determined and compared with those reported in the literature.
