Mathematical modeling of accelerated thermal transport inside particulate liquids

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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.