Collaborative Research: A Micropatterned Wettability Approach for Superior Boiling Heat Transfer Performance

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CBET-1235867PIs: Daniel Attinger (Iowa State Univ.) and C. Megaridis (UIC)This cross-institutional project straddles the areas of thermofluid engineering, materials science and optimization, with main goal to design, fabricate and study novel surfaces that are called ?superbiphilic.? These micro- and nanostructured surfaces juxtapose superhydrophobic areas (with strong affinities for water) with superhydrophobic areas (with strong affinities for water vapor). As such, they show superior performance in pool boiling by controlling the transport of the vapor and liquid phases in a parallel and optimal manner. The study will develop a novel coating-on-metal process, which is scalable and relevant to industrial heat exchangers. The main scientific challenge lies in understanding, controlling and optimizing boiling phenomena on the superbiphilic surfaces. For the first time, biphilic and superbiphilic surfaces will be fabricated on technically relevant, metallic substrates. The technology is based on sprayed-on patternable coatings, an industrial sector where US leadership is challenged from overseas. The research will develop a theoretical science base for boiling enhancement on biphilic and superbiphilic surfaces. The work is challenging because boiling involves multiphase and multiscale transport phenomena (evaporation starts in a sub-micrometer thick film, while detaching bubbles are millimeter-sized) and severely transient processes. To assist with the design and experiments, a modeling effort will be carried through. For simple surface topographies (or patterns of hydrophobic and hydrophilic domains), analytical models will be developed to explain the pool boiling enhancement in a qualitative manner. Computational fluid dynamic simulations will also be performed, to help understand the experimental data, identify the dynamic mechanisms responsible for the boiling enhancement, and evaluate the performance of complex surface topographies. The effort will feature a pattern design optimization approach to determine optimum topographies for boiling performance. The performance of the novel superbiphilic surfaces will be evaluated by a series of experiments, including surface wettability measurements, coating physical characterization, high speed visualization, as well as nucleation and pool boiling curves.The research, which involves rich fundamental phenomena in a variety of multidisciplinary topics, intends to deliver an innovative solution to transferring heat at superior rates in boiling configurations. The developments from this work will affect -among other technologies- heat exchangers, which are widely used in most energy-intensive industries, which collectively consume over 15 quadrillion Btu/yr in the US alone. Consequently, the non-incremental improvements resulting from this research have the potential to generate tremendous energy savings, and in turn, reduce energy waste and environmental pollution. Two graduate students will be educated in this program, and the team will reach out to underrepresented minorities in the Chicago area.