Drop impact phenomena and spray cooling on hot nanotextured surfaces of various architectures and dynamic wettability

Abstract

Spray cooling has been used to quench metal slabs during casting, cool nuclear reactors, suppress accidental fires, and remove heat from high-power density electronics. In particular, the miniaturization of electronic devices inevitably results in an increased power density or heat flux on the microelectronics surfaces and poses a threat of a thermal shutdown of such devices when cooling is insufficient. Surface nanotexturing effectively augments additional liquid-to-substrate surface area, thereby increasing cooling capability, as well as an effective heat transfer coefficient. In spray cooling, surface dynamic wettability also affects drop impact dynamics and subsequent coolant evaporation on a hot surface. Herein, we introduced various nanotextured surfaces and affected dynamic wettability using the so-called thorny-devil nanofibers, nickel nanocones, Teflon and titania nanoparticles, and zinc nanowires. The effect of these different nanoscale architectures on drop impact phenomena and subsequent evaporative cooling was investigated. These nanotextured surfaces were fabricated using various deposition methods, including electrospinning, electroplating, supersonic spraying, aerosol deposition, and chemical bath deposition. We found that the surface with greater dynamic wettability related to the hydrodynamic focusing considerably improved the heat removal capability by furthering the Leidenfrost limit and facilitating drop spreading. In particular, the thorny-devil nanofiber surface yielded the highest heat flux at all ranges of the Reynolds and Weber numbers. Spray cooling on a model electronic kit also confirmed that the thorny-devil nanofibers were most effective in cooling the surface of the model kit during multiple cycles of water spraying.

Dynamics of microdroplet generation via drop impact on a superhydrophobic micropore

“…), 1 Young-Su Ko (고영수), 1 Byeong Eun Jeon (전병은), 1 Prosenjit Sen ( ), 2 and Choongyeop Lee (이충엽) 1,a) I. INTRODUCTION Over the years, researchers have extensively investigated the dynamics of drop impact on solid surfaces due to its diverse applications in biomedical diagnostics, 1 food processing 2 and chemical industries, 3 electronic industries, 4 and rapid prototyping. 5,6 Notably, it has been demonstrated that drop impact on a mesh with micropores can serve as a mechanism to generate microdroplets.…”

Integrating a micro-mixing mechanism and on-line thermal processing for the large-scale ejection of polymeric liquid threads for producing ultrafine fibers

“…1 Many of those brous materials are produced from polymer solutions, [2][3][4] which may contain additives such as nanoparticles, nanotubes, or soluble precursors. 3,[5][6][7][8][9][10] The polymer matrix either serves as a template for micro/nanober fabrication or is the material of interest itself. The applications of such polymer bers are determined not only by the structure of the polymer's repeating building block or their physicochemical surface properties but also by their dimensions, such as their length and diameter.…”

Influence of the Nozzle-to-Surface Distance on Spray Cooling Efficiency

“…Later, Rybicki and Mudawar [10] concluded that the volumetric flux and droplet diameter are the most significant spray parameters influencing the heat transfer at spray cooling. Plenty of work has also been carried out on the heat transfer aspect of a single drop [11][12][13] or drop train flows [14][15][16][17]. Although they revealed that the droplet impact has a significant effect on the cooling performance, for a clear understanding of heat transfer associated with irrigation patterns during spray cooling, further research is still needed [18].…”