Coating engineering for boiling heat transfer toward immersion cooling

With the technological advancements in electronics, thermal management is becoming a concern that considerably affects the performance of electronic parts and systems, and two-phase immersion cooling is attracting attention due to its preferable cooling capacity. In immersion cooling, heat is dissipated by boiling that occurs on hot surfaces immersed in coolants. Therefore, it is essential to investigate boiling towards the realization and optimization of immersion cooling. Extensive studies have been carried out in terms of boiling heat transfer, e.g., bubble dynamics, heat transfer mechanisms, and critical heat flux, which convincingly indicate that boiling heat transfer greatly depends on surface characteristics and liquid properties as well as interactions between surfaces and liquids. As a consequence, many technologies have been applied to tailor-made or engineered surfaces to achieve an enhancement in boiling. Accordingly, this chapter will concentrate on technologies that produce thin film coatings on target surfaces, like CPU and memories in electronics, enabling high-efficient boiling performance and having good compatibility with electronics. Specifically, the chapter will be organized mainly with the following sections: introduction, fundamentals of boiling, coating technologies for boiling enhancement, and exploration of the enhancement mechanism. Through this work, it is expected to provide general insights into boiling heat transfer and give suggestions regarding the future directions of boiling heat transfer research.