This investigation involves flow boiling of non-azeotropic and azeotropic binary mixtures in two types of micro-scale heat transfer enhancement structures, namely micro-channels and micro-pin fin arrays. Forced convection boiling of binary mixtures in channels of conventional size, as well as flow boiling of pure fluids in micro-scale structures has been studied extensively. However, forced convection boiling of binary mixtures in micro-scale structures remains largely unexplored.
Intellectual Merit: An experimental approach will be taken to investigate and quantify heat transfer rates, two-phase pressure drops, critical heat fluxes, and flow instabilities in situations involving forced convection boiling of binary mixtures in small channels. The influence of mixture composition and microstructure geometry on the boiling process will be explored, and accurate modeling tools will be developed. Possible heat transfer degradation associated with forced convection boiling of mixtures in micro-scale structures will be examined and the mechanisms leading to degradation will be identified.
Broader Impacts: The research will impact a number of technologies, including but not limited to use of miniaturized heat sinks for high-heat-flux cooling applications, as well as the design of miniature chemical reactors. The project will expose graduate, undergraduate, and high school students to micro-scale flow boiling transport processes through integrated teaching, research, and outreach activities. Existing institutional programs that target involvement of underrepresented groups will also be utilized.
The project investigated single-phase flow, two-phase flow, and flow boiling of pure fluids and binary mixtures in the two common types of micro-scale heat transfer enhancement structures, namely micro-channels and micro-pin-fin arrays. An experimental approach was taken to study the various transport phenomena including pressure drop and heat transfer. The experimental study was complemented by numerical simulation and modeling. Effects of mixture composition and microstructure geometry on the transport phenomena were explored, and accurate predictive tools were developed. Intellectual Merit: While the subject matters of binary mixture fluid flow and heat transfer in conventional millimeter or larger diameter channels have been studied quite extensively in the past, thermal-hydraulic aspects of binary mixture single-phase flow, two-phase flow, and flow boiling in micro-scale structures remain largely unexplored. The effects of mixture composition and micro-scale flow passage size on the transport phenomena were investigated. Empirical correlations were developed to describe the complex transport process. Broader Impacts: The outcome of the proposed work had a broader impact on a number of applications, including development of functionalized liquid mixture coolants for single-phase and two-phase miniature heat sinks intended for high-heat-flux cooling applications as well as effective thermal design of miniature chemical reactors. The project also exposed graduate and undergraduate students to the cutting-edge micro-scale flow boiling transport process through integrated teaching and research.
