Mathematical modeling of accelerated thermal transport inside particulate liquids

负载纳米粒子的流体具有增强的导热性能，但这一现象仍然缺乏解释。这种增强是相当显著的，因为引入非常少量的纳米颗粒可以导致不成比例的高导热增加。加速传导的优点包括加热质量的更快蒸发或燃料液滴的更快燃烧。这个项目调查了这一显著现象背后的机制。如果找到了根本原因，就可以利用它来创造更好的冷却剂和高能材料，从而改进热交换器、燃气轮机和内燃机等设备。此外，通过确保液体燃料的快速和完全燃烧，同时消除废气中燃料的浪费和有害存在，它将有助于提高发动机的能源效率和控制污染。加速热输运的关键原因可以归结为悬浮纳米粒子的布朗运动。随机移动的亚微米固体就像液体中的微小搅拌器，表现出类似于搅拌勺子的效果，帮助冷却一杯热饮料。不幸的是，过去的研究一直低估了布朗的影响，未能恰当地量化这种布朗贡献。在本项目中，这一不足将通过一种基于脉动流体动力学和热传递的新的统计力学描述来解决。因此，由于颗粒的随机运动，可以从液体体积的微尺度对流中准确地估计出增强的热流密度。这将与其他一些潜在的重要因素相结合，如局部热点的创建、潜热漂移和自然对流。因此，这项研究将揭示这些过程之间的相互作用如何影响纳米流体中的能量转移。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Fluids laden with nano-particles have enhanced heat conduction properties, but this phenomenon is still lacking explanation. This enhancement is quite dramatic because introduction of very small amount of nano-particles can cause disproportionately high increase in heat conduction. Advantages of the accelerated conduction include quicker evaporation of a heated mass or faster combustion of fuel drops. This project investigates the mechanism underlying this remarkable phenomenon. If the underlying cause is identified, it can be exploited in creating better coolant and energetic materials, leading to improvements in devices like heat exchangers, gas turbines and internal combustion engines. Moreover, it will help in energy efficiency and pollution control in engines by ensuring fast and complete combustion of liquid fuels while eliminating wasteful and harmful presence of the fuel in the exhaust. The key reason behind the accelerated thermal transport can be attributed to the Brownian motion of the suspended nano-species. Randomly moving submicron solids act like tiny stirrers inside the liquid manifesting an analogous effect of a stirring spoon helping to cool down a hot cup of beverage. Unfortunately, past studies have failed to properly quantify this Brownian contribution by consistently underpredicting its influence. In the present project, this deficiency would be addressed by a new statistical mechanics description based on fluctuating hydrodynamics and heat transfer. Consequently, the enhanced thermal flux can be accurately estimated from the micro-scale convection by the liquid bulk due to the stochastic motion of the particles. This would be coupled with a few other potentially significant factors like creation of localized hot spots, thermophoretic drift and natural convection. Thus, the study will reveal how the interplay among these processes combined affects the energy transfer in nanofluids.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.