Nucleate boiling is the most effective and technically controllable heat transfer mechanism. The main goal in boiling heat transfer enhancement is lowering the surface overheat for a given heat flux and increasing critical heat flux, which could be achieved by modifying surfaces' micro and nano structure and its wettability. In this dissertation we present development of (i) biphilic structured surfaces based on polydimethylsiloxane-silica coating and (ii) laser structured hydrophilic surfaces. Our designed experimental setup comprises high-speed infrared thermography for measuring transient temperature fields underneath thin metal foils and video camera to observe growing vapor bubbles. Results showed that hydrophobic spots on biphilic surfaces promote onset of nucleation and their size influences bubble detachment diameter as well as nucleation frequency. By varying biphilic pattern we managed to define positions of active nucleation sites, delay occurrence of horizontal coalescences and thus increase boiling stability. This resulted in lower overheat and higher critical heat flux. It was also concluded that the optimal biphilic pattern could only be determined for a particular heat flux. For laser structured surfaces the best results were achieved on the heterogeneously wettable sample with microcavities present on the surface. The highest number of active nucleation sites corresponded to the locations of microcavities, which is also supported by existing nucleation criteria. This surface demonstrated even lower superheat than all other tested biphilic surfaces. Finally, we propose a new approach to evaluating the boiling process on the basis of probability density of wall-temperature, calculated from spatio-temporal thermographs of the boiling surface. Instead of a single data point on the boiling curve, the presented wall-temperature distributions provide spectra of information that could be also used in evaluating boiling stability. This opens a new path towards a better understanding and the development of phase-change heat transfer technology.
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