纳米流体应用于内燃机冷却水腔强化传热的导热机理分析

Basic Research on Enhancing Mechanisms of Heat Conduction of Nanofluids for Its Application in Cooling Water Jacket of IC Engine

用分子动力学模拟对纳米流体的导热系数进行计算,并对纳米流体处于微观层次的导热强化机理进行模拟.研究发现,纳米流体的导热系数相对基础液有明显提升,纳米颗粒的体材及纳米颗粒的体积分数等因素会对纳米流体的导热系数造成影响.通过分子动力学模拟,证实了纳米颗粒表面液体吸附层、纳米颗粒微运动的纳米流体导热强化机制;通过径向分布函数分析纳米流体的微观结构,发现纳米流体总体表现出类似于固体的微观结构,提出这种由于纳米颗粒影响导致的纳米流体的微观结构改变也是纳米流体导热强化的机制.所分析的纳米流体导热强化机制能够为进一步建立纳米流体导热预测物理模型提供理论支持.

This study calculates the thermal conductivities of nanofluids, as well as examines enhancing mechanisms of heat conduction of nanofluids through Molecular Dynamics simulations. The thermal con- ductivity of nanofluids is increased compared with that of base fluid, while the materials of nanoparticles, and volume concentration of nanoparticles affect the promotion degree. Molecular dynam- ics simulations confirm the absorption layer around nanoparticles, and the micro-motions of nanoparticles are the enhancing mechanism of heat conduction in nanofluids. Radical Distribution Function analysis shows that nanofluids present a microscopic structure characteristic which is similar to that of solid. The changed microscopic structure of nanofluids due to addition of nanoparticles is suggested to be another mechanism of heat conduction of nanofluids. The mechanisms of heat conduction of nanofluids are the basis for proposing theoretical predictions models of thermal conductivity of nanofluids.