The Impact of Nanofluids on Droplet/Spray Cooling of a Heated Surface: A Critical Review

Abstract

Cooling by impinging droplets has been the subject of several studies for decades and still is, and, in the last few years, the potential heat transfer enhancement obtained thanks to nanofluids’ use has received increased interest. Indeed, the use of high thermal conductivity fluids, such as nanofluids’, is considered today as a possible way to strongly enhance this heat transfer process. This enhancement is related to several physical mechanisms. It is linked to the nanofluids’ rheology, their degree of stabilization, and how the presence of the nanoparticles impact the droplet/substrate dynamics. Although there are several articles on droplet impact dynamics and nanofluid heat transfer enhancement, there is a lack of review studies that couple these two topics. As such, this review aims to provide an analysis of the available literature dedicated to the dynamics between a single nanofluid droplet and a hot substrate, and the consequent enhancement or reduction of heat transfer. Finally, we also conduct a review of the available publications on nanofluids spray cooling. Although using nanofluids in spray cooling may seem a promising option, the few works present in the literature are not yet conclusive, and the mechanism of enhancement needs to be clarified.

Magnetic Self-Healing Composites: Synthesis and Applications

“…Droplet splashing and manipulation onto surfaces is a key phenomenon for applications such as microfluidic systems, microreactors and electronic refrigerators [141,142]. Tailoring the chemistry and topography can lead to the design of non-wetting surfaces with substantially diminished contact when exposed to liquids performing as, for example, excellent lubricants [143].…”

Experimental investigation into spray cooling heat transfer performance of Al2O3-water nanofluid with different subcooling degrees

“…Nonetheless, most of the droplets still adhered to the heated surface, thereby increasing the wetted area for cooling purposes. Aksoy et al 18 conducted a review of the published literature on nanofluid spray cooling, and concluded that nanofluids have a high potential for improving the heat transfer performance of spray cooling systems. However, they argued that further experimental research is required to determine the performance and operational limits of such fluids when cooling via droplet impact.…”

Spreading of a droplet impacting on a smooth flat surface: how liquid viscosity influences the maximum spreading time and spreading ratio

“…Droplet impact onto solid surfaces is a very popular research field thanks to an extensive variety of applications with the examples including surface coating, 1 forensic science, 2 inkjet printing, 3,4 and spray cooling. [5][6][7][8] In particular, the maximum spreading ratio β max , i.e., the ratio of the maximum spreading diameter D m to the initial droplet diameter D 0 , determines the performance of these processes. 9 As the fluid and surface properties govern droplet spreading, the following non-dimensional numbers must be considered for its modeling:…”