纳米颗粒悬浮液池内泡状沸腾机理

研究了添加不同性质、不同体积浓度的纳米颗粒后对液体池内泡状沸腾换热的影响和相应的物理机制,并对3种不同体积浓度的Fe及A l2O3纳米流体进行了池内沸腾的实验研究.分析表明:纳米颗粒的加入,将增加液体的有效导热系数和粘度,降低基液的表面张力;另一方面,由于部分纳米颗粒会在加热表面形成沉积,改变了加热表面活化凹坑的尺度及分布,从而对成核和气泡成长过程产生影响.因此,纳米流体池内泡状沸腾传热强化与否,是多种因素综合作用的结果.实验结果证实了上述分析.根据“对流汽化”模型给出了去离子水与体积分数为2?纳米流体沸腾换热关系式,与实验值符合较好.

Pool boiling heat transfer mechanism of nano-particle suspensions

The influences of nano-particles with different volumetric density in liquid on pool boiling heat transfer are studied.The pool boiling heat transfer mechanism of nanofluids is analyzed and an experimental study on pool boiling heat transfer for water-Fe and water-Al_2O_3nano-fluids with three different volumetric densities is conducted.The results show that nano-particles increase the thermal conductivity and viscosity,decrease the surface tension of boiling fluid,thus influence the inner heat transport process in boiling liquid;on the other hand,nano-particles might deposit on the boiling surface and change the nucleation activity of the boiling liquid.The boiling heat transfer for nano-fluids would be enhanced or deteriorated depending on the summarization of these effects.This analysis is proved by the experimental results.Based on the "convection-vaporization" model,boiling heat transfer relation formula for deionized water and 2% Fe-water nano-fluid is obtained,which conforms to the experimental data.