The project goals are twofold; 1) yield an understanding of the chemistry of an inorganic aqueous solution that is sufficient to develop a ?designer fluid? for a particular heat transfer application and 2) establish the ability of such a designer fluid to enhance heat transfer in the phase change device (heat pipes, recuperators, and/or thermosiphons) within which it is to be used. The understanding of the chemistry, the first part of the project, will be quantified to establish the impact of the type and amount of the chemical constituents. A library of various applications and suggested chemical constituents will be developed. What is needed to passivate various materials, to relate the mixture constituents and their molality to passivation, hydrophilicity, surface deposition and microstructure will be established. The second part of the project is to quantify the capacity of a designer fluid to enhance heat transfer in the device in which it is to be used. A correlation between the deposition of material and construction of the micro-porous coatings to the chemistry, pH and temperature of the mix will be developed. The heat transfer will be related to the amount and type of constituents and their capacity to construct micro-porous coatings on a surface and to the hydrophilicity and capillarity of the surface microstucture. The impact of such a designer fluid on the effectiveness of various types of wicking will complete the project.
Water is one of natures best heat transfer fluids when phase change is involved because it has the highest heat of evaporation. Unfortunately water is also a good oxidizer and can lead to corrosion and, if a metal, hydrogen production that can seriously degrade the heat transfer performance. Presently, water can only be used with metals like copper. In this work, a novel, inorganic aqueous solution is developed for use with aluminum and other material heat pipes and thermosiphons that will improve the heat transfer performance by as much as a factor of two. The chemical reactions responsible for passivating the device material interior and preventing generation of non condensible gases (NCG) will be explained. Being able to use a phase change heat transfer fluid that has the equivalent or better heat transfer performance than water in a range of different materials will have a significant impact on many aspects of the power generation, process and electronics industries and our ability to harvest waste heat.
