Forced convection heat transfer has a very wide application base. It is inherent to numerous processes and equipment that affect our day-to-day lives such as heat exchangers and heat sinks in power generation, thermal management, space transportation, water purification and defense sectors. In forced convection of liquids in channels/pipes, due to the analogous dependence of flow friction and heat transfer performance on fluid flow velocity and wall/surface characteristics, it was found by prior researchers that any attempt to lower friction at the walls inevitably results in decreased heat transfer rate and efforts to augment heat transfer almost always result in increased frictional flow resistance. While enhanced heat transfer is beneficial, increased friction at the walls demands more electricity consumption in the form of pumping power required to overcome it. This proposal aims to resolve this important and arduous problem that has attracted much research attention in the last few decades i.e., it enables friction reduction near the walls for fluid flow but for the first time, with negligible impact on heat transfer performance by employing liquid-saturated hierarchical micro/nanoporous surfaces. The focus will be on forced convection of liquids without phase change. The proposed work has broader impacts on science and society, which will be demonstrated through curriculum integration and state-of-the-art research/classroom opportunities at the undergraduate and graduate levels at the New Mexico State University. This activity will directly help in developing a diverse, globally competitive STEM workforce that would understand and address critical issues of national interest in energy.
For achieving the project goals and objectives, robust hierarchical micro/nanoporous surfaces of various roughness topologies will be fabricated on internal surfaces of flow channels using a novel etching technique, and their wetting, aging, and robustness aspects will be characterized using precise weight measurement and fluorescence microscopy techniques. To verify the theoretical predictions that showed substantial potential of the concept, experimental investigation of forced convective heat transfer performance of common coolants will be carried out in mini/microchannels with water saturating the micro/nanoporous wall surfaces. The recorded data of pressures, temperatures and flow rates will be post-processed to obtain an energy-efficiency metric, which will be the increased Nusselt number for the same pumping power required to pump the same liquid through a same sized channel with regular/smooth surfaces. Outcomes as a result of successful completion of the project will generate new knowledge base for realizing significant energy efficiencies in forced convective transport by providing novel fundamental insights on surface -philicity and robustness, flow stability and thermal transport, and their dependence on surface topology.
