【摘要】 以水-多壁碳纳米管(MWNT)组成的纳米悬浮液为工质,在不同运行压力和不同悬浮液质量分数下对平板上碳纳米悬浮液的池内沸腾换热特性以及临界热流密度(CHF)进行了实验研究.结果表明:压力对沸腾换热系数和CHF有强烈影响,沸腾换热系数强化效率和CHF强化效率随压力降低而大幅度增加;碳纳米管悬浮液质量分数对沸腾换热系数和CHF也有重要影响,存在着一个最佳质量分数对应最大换热系数强化效率,该最佳质量分数为2.0%.研究证明,以水-多壁碳纳米管组成的纳米悬浮液可以明显地强化低压条件下池内沸腾换热特性.更多还原

【Abstract】 An experimental study was performed to understand pool nucleate boiling heat transfer of water-carbon nanotubes(CNT) suspensions on a flat heating surface at different sub-atmospheric pressures and different carbon nanotube mass fractions.The experimental results indicate that both heat transfer coefficient(h) and critical heat flux(CHF) of CNT suspensions increase greatly with the decreasing pressure as compared with those of water.Nanotube mass fraction also has significant influence on the both boiling heat transfer coefficient and CHF of CNT suspensions.The heat transfer coefficient and the CHF increase slowly with the increase of the mass fraction at low mass fraction conditions.However,when the mass fraction is over 2%,the CHF is basically close to a constant,and the heat transfer coefficient slowly deteriorates.There exists an optimum mass fraction for CNT suspensions which corresponds to the maximum heat transfer enhancement and this optimum mass fraction is 2% at all test pressures.The experimental study confirms that the boiling heat transfer characteristics of water under sub-atmospheric pressures can evidently be strengthened by adding a little of CNT into water.更多还原