*1.1. Methods for Intensifying Boiling Heat Transfer*

In recent years, researchers have thoroughly studied different techniques for intensifying boiling heat transfer, such as adding nanoparticles to the base fluid or modifying the surface characteristics of the boiling surface, namely its roughness, porosity, wettability, wickability, etc. [13–18]. Surface modification may be performed on the macro-, micro- or nanoscale [11]. The techniques for the modification of surface morphology can generally be divided into physical and chemical categories [19]. Common physical techniques include electro-deposition [20] and pulsed laser deposition [21], while in most studies, the chemical techniques are chemical vapor deposition [22], the sol-gel technique, and electrochemical deposition [23]. Overall, surface modification aims to alter the surface wettability and microstructure, which have a profound impact on the boiling process and the associated heat transfer parameters [16,24,25]. Free surface energy, roughness of the surface, and its micro- and nanotexture have a strong influence on wettability [10,26,27]. Based on the contact angle of a liquid droplet on the surface, the latter can be classified as phobic or philic to the liquid. As water is the most common testing medium, the surfaces are typically classified as hydrophilic (contact angle < 90◦ ) or hydrophobic (contact angle > 90◦ ). Based on previous experimental findings, the ONB will occur at a lower superheat, and CHF will be decreased on hydrophobic surfaces, while hydrophilic surfaces will exhibit delayed ONB, but increased CHF [10,28,29].
