为分析单层石墨烯纳米片对核态池沸腾换热的影响机理，对基液为R141b、分散相为单层石墨烯纳米片的纳米制冷剂的核态池沸腾换热特征进行了测定，采用Hot Disk热物性分析仪和铂金板法分别测定了石墨烯纳米制冷剂的热导率和表面张力，采用接触角测量仪和扫描电子显微镜（SEM）观测了沸腾后加热表面的润湿性和形貌特征。实验中，单层石墨烯纳米片的质量百分含量（ω）为0.02%~0.50%，实验压力为一个标准大气压，热流密度为20~200 kW/m2。实验结果表明：单层石墨烯纳米片的加入，使制冷剂R141b的核态池沸腾换热得到强化；当ω=0.2%时，换热系数提高比例出现峰值，为57.7%。伴随ω的增加，石墨烯纳米制冷剂的热导率增大、表面张力减小，沸腾表面润湿性增强且微腔数先增后减，综合作用的结果导致存在一个最佳的单层石墨烯纳米片浓度（即ω=0.2%）使换热系数最高。

In order to analyze the influence mechanism of singlelayer graphene nanoplatelets (GNPs) on nucleate pool boiling heat transfer,the nucleate pool boiling heat transfer characteristics of nanorefrigerants formed by dispersing singlelayer GNPs were experimentally investigated.The thermal conductivity and the surface tension of GNP nanorefrigerants were measured by Hot Disk thermal constants analyzer and platinum plate method,respectively.The wettability as well as morphology of heating surface after boiling were observed by contact angle analyzer and scanning electron microscope (SEM).The singlelayer GNP mass fraction (ω) ranged from 0.02% to 0.5%,the saturation pressure was atmospheric pressure,and the heat flux ranged from 20 to 200 kW/m2.The experimental results show that the addition of singlelayer GNPs enhances the nucleate pool boiling heat transfer of refrigerant R141b,and the enhancement reaches the maximum value of 57.7% at ω of 0.2%.With the increase of ω,the thermal conductivity of graphene nanorefrigerant increases and the surface tension decreases.The surface wettability increases also,while the number of microcavities increases and then decreases.The combined effects of above factors result in an optimal singlelayer GNP mass fraction (i.e.ω=0.2%) for achieving the maximum heat transfer enhancement.

TB69;TK124

上海市自然科学基金（No.19ZR1422300）；上海市青年东方学者人才计划（QD2016045）