A specially engineered surface that can allow liquids to boil without bubbling is described in a paper in Nature this week by scientists at KAUST.
Suppression of the bubbling phase could help to regulate heat exchange and reduce damage to surfaces, or even explosions. These properties would be advantageous for use in industrial situations such as nuclear power plants, where vapor explosions are best avoided.
The above video clip shows a comparison: on the left-hand side, liquid boils around a hot metal sphere; on the right-hand side, a treated surface, and bubble-less boiling.
Dr. Ivan Vakarelski and colleagues use a textured, highly water-repellent surface to control the boiling state of a liquid so that boiling takes place only in a continuous vapor film at the hot surface. The no-bubbling boiling phase is known as the Leidenfrost regime, named after the scientist who studied water drops skittering on a hot skillet owing to their levitation on a cushion of vapor. KAUST scientists Dr. Ivan Vakarelski, Dr. Jeremy Marston, and Professor Sigurdur Thoroddsen; Professor Neelesh Patankar of Northwestern University; and Professor Derek Chan of Melbourne University, collaborated in the study.
All the experimental work for the paper was conceived and conducted at KAUST’s High Speed Fluids Lab led by Prof. Thoroddsen. The experiments were also supported by the Machine Workshop, Electronics Workshop, and the Advanced Nanofabrication, Imaging, and Characterization Core Lab facilities.
The observations reported by Dr. Vakarelski and colleagues contrast with those made using smooth surfaces, where upon cooling the vapor film collapses and the system switches explosively to nucleate (bubbling) boiling. With the recent development of a wide variety of laboratory-designed and commercially available textured surface coatings the effect on the thermal exchange shown in the paper opens possibilities for new applications of such coatings, ranging from the design of efficient heat-exchange devices to technologies for aqueous drag reduction.
