Experimental investigation on pool boiling heat transfer over micro textured, additive manufactured surfaces, and impact of extended exposure to boiling heat transfer

The ever-increasing population and rising living standards require the development of high-performance, efficient, and safe technologies. Compact thermal systems face challenges due to limited space availability, while waste heat reduction and efficient cooling become crucial. Traditional thermal management methods have already reached their limits, and alternative technologies utilizing phase-change materials, heat pipes, or miniature/mini chambers are required to overcome heat removal limitations and achieve effective cooling in compact systems. Pool boiling heat transfer offers high-performance cooling opportunities for thermal problems especially electronics limited with high heat fluxes, and have been extensively studied over the last eight decades. This sensitive cooling method is influenced by a vast number of parameters, while the interplay of these parameters introduces a significant level of intricacy, making accurate predictions challenging. The predictive expressions for a broader spectrum of operating conditions, fluid chemical composition, or even surface topography are still inefficient in order to forecast the fundamental heat transfer measures of critical heat flux (CHF) and heat transfer coefficient (HTC). Indeed, this study aims to enhance boiling heat transfer (BHT) by incorporating artificial cavities through microdrill manufacturing and additive manufactured (AM) microchannel surfaces. Additionally, the development of oxide layers and their impact on surface performance are investigated. The boiling performance of surfaces with micro-drilled artificial cavities is analyzed under different operating conditions. In addition, the study examines the effect of microchannel geometries, specifically rectangular, V-shape, and inverse V-shape channels fabricated using laser powder bed fusion, on BHT. The influence of surface roughness on heat transfer is compared between additive manufactured surfaces and conventionally polished surfaces. Oxide layer development and its effect on heat transfer are explored on copper substrates under various operating scenarios. In order to conduct the experiments, an in-house manufactured and fully automated boiling setup, which resist to high temperature and pressure was constructed. De-ionized (DI) water and 3M™ Novec™ hydrofluoroether (HFE-7100) Engineered Fluid were preferred as working liquids to be suitable for the cooling of electronic systems priorly. In this study, the tests were conducted at between 0 - 10 K subcooling temperatures and 1 - 1.5 bar pressures. Experimental analysis includes contact angle measurements, confocal microscopy, scanning electron microscopy, X-ray diffraction, and high-speed imaging for bubble formation. These investigations contribute to understanding and improving heat transfer performance in boiling systems.