Entropy Based Design and Convective Heat Transfer in Multiphase Flows

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Driven by the increasing need to improve energy efficiency of thermal / fluid systems and reduce greenhouse gas emissions, researchers are utilizing entropy based design as an emerging tool to identify and minimize system flow losses. The use of the Second Law of Thermodynamics has been well established for system analysis, however to a much lesser extent for spatially tracking the local rates of entropy production throughout a flow field. In particular, entropy transport in multiphase flows has a significant potential to highlight new ways to improve energy conversion and efficiency. This research proposal examines convective heat and entropy transport processes in multiphase flows with droplets and particles. Both numerical and experimental studies are proposed to better understand the transport phenomena. Applications to two specific multiphase systems are examined: thermochemical hydrogen production with a copper-chlorine (Cu-Cl) cycle, and droplet impact on icing surfaces. The research program aims to develop new methods of entropy based design of multiphase systems with droplets and particles, specifically to provide new insight and improvements in: 1) transport processes; 2) solution accuracy; and 3) experimental measurements. The applications focus on multiphase flows in the Cu-Cl cycle and icing of surfaces (i.e., ships; overhead power lines). In the former case (Cu-Cl cycle), solidification of droplets occurs during processes of heat recovery of molten CuCl and drying of copper(II) chloride droplets. In the latter case (icing), the heat flows during droplet impact and ice accretion on a surface include conduction through the unfrozen surface film and ice, convective cooling, release of latent heat by the freezing droplets, and kinetic energy and supercooling of the incoming droplets.  The objectives of the research are to develop new design tools that actively incorporate entropy and the Second Law for more accurate and robust prediction and measurement of multiphase flows with droplets and particles. Specific applications involve the Cu-Cl cycle and icing of surfaces (ships; overhead power lines). The objectives are to extend the methodology of entropy based design so as to improve the energy efficiency of multiphase flows by minimizing the entropy generation and also provide new insight into the multiphase processes by measuring and characterizing the flow irreversibilities. Another goal of this research program is to use entropy based design to improve the thermal efficiency of the Cu-Cl cycle so as to demonstrate commercial viability at a large industrial scale of operation.