Non-isothermal crystallization of aqueous graphene oxide suspensions
WANG Xiao1,YAO Xiao-li1,HOU Jian-feng1,FAN Li-wu1,XU Xu2,YU Zi-tao1,HU Ya-cai1
1. Institute of Thermal Science and Power Systems,Zhejiang University,Hangzhou 310027,China；2. College of Metrological and Measurement Engineering,China Jiliang University,Hangzhou 310018,China
The thermal conductivity of phase change materials can be efficiently increased by adding graphene nanoadditives to form suspensions. The presence of the graphene nanoadditives is expected to have considerable influence on the solid-liquid phase change characteristics of the suspensions. The aqueous suspensions in the presence of graphene oxide nanosheets at dilute concentrations were characterized via the non-isothermal crystallization method on a differential scanning calorimeter. The dependence of the supercooling degree of the suspensions on the concentration (up to mass fraction of 1%) and the cooling rate was analyzed. Results show that the supercooling degree is lower than that of pure water due to the presence of the graphene oxide nanosheets and decreases gradually with increasing the mass fraction. The lowering of the supercooling degree was nearly 5 ℃ at the highest mass fraction of 1%. In addition, the supercooling degree was shown to rise slightly with increasing the cooling rate, whereas the relative variation of the supercooling degree with respect to mass fraction was unaffected. The utilization of aqueous graphene oxide suspensions as cold storage media can lower the supercooling degree,whereas the non-isothermal crystallization processes are unable to be shortened．
1］ 张仁元. 相变材料与相变储能技术［M］. 北京：科学出版社,2009．
［2］ 朱冬生,李新芳,汪南,等. 纳米流体相变蓄冷材料的基本特性与应用前景［J］. 材料导报,2007,21(4)：87-91．
ZHU Dong-sheng,LI Xin-fang,WANG Nan,et al. Fundamental properties and application prospect of the phase change nanofluid as a cold storage material ［J］. Materials Review,2007,21(4)：87-91．
［3］ 刘玉东,刘夔宁,何钦波,等. 低温纳米复合相变蓄冷材料热物性研究［J］. 工程热物理学报,2008,29(1)：105107．
LIU Yu-dong,LI Kui-ning,HE Qin-bo,et al. Study on thermal properties of low temperature nanocomposites for phase change cool storage ［J］. Journal of Engineering Thermophysics,2008,29(1)：105-107．
［4］ WU Shu-ying,ZHU Dong-sheng,LI Xin-fang,et al. Thermal energy storage behavior of Al2O3-H2O nanofluids ［J］. Thermochimica Acta,2009,483(1/2)：73-77．
［5］ 杨硕,朱冬生,吴淑英,等. Al2O3-H2O纳米流体相变蓄冷特性研究［J］. 制冷学报,2010,31（1）：23-26．
YANG Shuo,ZHU Dong-sheng,WU Shu-ying,et al. Study on phase-change cold storage characteristics of Al2O3-H2O nanofluids ［J］. Journal of Refrigeration,2010,31（1）：23-26．
［6］ BIGG E K. The supercooling of water ［J］. Proceedings of the Physical Society, Section B,1953,66（8）：688-694．
［7］ ANGEL C Z. Supercooled water ［J］. Annual review of Physical Chemistry,1983,34: 593-630．
［8］ 洪荣华,孙志坚,吴杰,等. 成核添加剂减小冰蓄冷溶液过冷度的实验研究［J］. 浙江大学学报：工学版,2004,39(11)：1797-1800．
HONG Rong-hua,SUN Zhi-jian,WU Jie, et al. Experimental study on reduce supercooling degree of ice storage solution using nucleation additive ［J］. Journal of Zhejiang University:Engineering Science,2004,39(11)：1797-1800．
［9］ CHEN Ying,JIA Li-si,MO Song-ping. Experimental investigation of crystallization process of nanofluid by DSC ［J］. Journal of South University:English Edition,2010,26(2)：359-363．
［10］ 贾莉斯,陈颖,莫松平. 二氧化钦纳米流体的固液相变特性［J］. 工程热物理学报,2011,32（11）：1913-1916．
JIA Li-si,CHEN Ying,MO Song-ping. Solid-liquid phase change property of titanium dioxide nanofluid ［J］. Journal of Engineering Thermophysics,2011,32（11）：1913-1916．
［11］ HE Qin-bo,WANG Shuang-feng,TONG Ming-wei,et al. Experimental investigation on nucleation supercooling degree of TiO2-H2O nanofluids for cool storage ［J］. Energy Conversion and Management,2012,64:199-205．
［12］ GONG Wei,XIAO Hong-yi,YANG Zhen,et al. Study of the subcooling phenomenon of phase change material with different nanoparticlcle additives for energys storage ［C］//Proceedings of the 8th International Symposium on Heat Transfer. Beijing: ［s.n.］, 2012:16．
［13］ KOUSKSOU T,RHAFIKI T,MAHDAOUI M,et al．Crystallization of supercooled PCMs inside emulsions: DSC applications ［J］. Solar Energy Materials and Solar Cells,2012,107:28-36．
［14］ WANG Ji-feng,XIE Hua-qing,XIN Zhong. Thermal properties of paraffin based composites containing multi-walled carbon nanotubes ［J］. Thermochimica Acta,2009,488(1/2)：39-42．
［15］ YU Zi-tao,FANG Xin,FAN Li-wu,et al. Increased thermal conductivity of liquid paraffin-based suspensions in the presence of carbon nano-additives of various sizes and shapes ［J］. Carbon,2013,53:277-285．
［16］ JIA Li-si,CHEN Ying,MO Song-ping. Solid liquid phase transition of nanofluids ［J］. International Journal of Heat and Mass Transfer,2013,59:29-34．
［17］ YU Wei, XIE Hua-qing, CHEN Wei. Experimental investigation on thermal conductivity of nanofluids containing graphene oxide nanosheets ［J］. Journal of Applied Physics,2010,107(9)：094317．
［18］ TESSY THERES B, SUNDARA S R. Investigation of thermal and electrical conductivity of graphene based nanofluids ［J］. Journal of Applied Physics,2010,108(12)：124308．
［19］ SOUJIT S G,SIVA V M,SREEPRASAD T S,et al. Thermal conductivity enhancement of nanofluids containing graphene nanosheets ［J］. Journal of Applied Physics,2011,110(8)：084302．
［20］ 刘东方. 潜热型水基氧化石墨烯纳米流体的制备及其过冷特性研究［D］. 重庆：重庆大学,2012:18-67．
LIU Dong-fang. Study of preparation and supercooling characteristics of graphene oxide nanofluids as phrase change material ［D］. Chongqing:Chongqing University,2012:1867．
［21］ 杨梅,赵长颖. 添加纳米颗粒的石蜡非等温凝固过程研究［J］. 热科学与技术,2013,12(1)：47-51.
YANG Mei,ZHAO Chang-ying. Investigation on non-isothermal solidification of paraffin with nano-particle additives ［J］. Journal of Thermal Science and Technology,2013,12(1)：47-51．
