Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 25, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dissertation advisor: Dr. Hongbin Ma. Vita. Includes bibliographical references.

The development of a mid-temperature range (250°C--500°C) heat pipe for high heat flux applications has been the focus of numerous researchers during the last 40 years. However, until this work a viable working substance for the heat pipe has eluded researchers. While the most mentioned element has been sulfur, its unusual viscosity-temperature relationship has prevented the commercialization of a sulfur-based heat pipe. / The recent development (and patenting) of the McGill heat pipe revived the question of whether sulfur would be viable in such a unit. Extensive testing showed that it is possible to make a high heat flux heat pipe with sulfur as the working substance. Given the lack of scientific details about the McGill heat pipe, a focused research program was undertaken to quantify the operation of the McGill heat pipe prior to studying the sulfur based unit. / One study looked at the two-phase flow characteristics of the McGill heat pipe. Both qualitative (videos) and quantitative data like the pressure drop and returning velocity were measured as a function of gas flow rate. Moreover, a new non-dimensional parameter, the modified swirler number was proposed. Further, the Lockhart-Martinelli method was used to analyze the pressure drop. / In the McGill heat pipe, the centrifugal force that is produced by the vortexing flow pushes liquid up against the walls and increases the critical heat flux. A theoretical model consisting of 4 sub-models was developed to predict the critical heat flux for defined situations. / The development of the sulfur-based heat pipe followed the empirical and mathematical modeling work that was carried out. A McGill heat pipe with sulfur as the working substance was designed, built and tested. The design was arrived at by considering the modeling work that was originally carried out. A number of interesting features were discovered with the sulfur-based heat pipe. A model based on mass, energy, and flow balances between the condenser and the evaporator was also developed. The model can be used to calculate the void fraction, quality, wall temperature, local heat flux distribution, heat load, cooling flow rate, and working substance temperature. The experimental results fit well the calculated ones.

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