Air conditioning, Climate, Equipment and supplies, Design and construction
This paper examine a passive cooling system for a humid climate. This system will be divided into two parts, a radiative system and an evaporative system combined into a roof pond system. Performance of the radiative system will be enhanced through the use of a selective cover which will make use of an atmospheric window between 8 and 13um. An attempt will also be made to thermally isolate the radiative system from convective gains with the evaporative system. The evaporative system will consist of a water, solvent and dye layer over the selective cover of the radiative system. The performance of the evaporative system will be enhanced by virtue of the increased vapor pressure made available through the use of solvents. The main solvent to be examined shall be methanol. The increased vapor pressure shall sufficiently increase the rate of evaporative cooling to a point where useful cooling is obtained even under high humidity conditions. It was found that a solution with a 0.8 mole fraction of methanol in the evaporative system could cool a sufficiently large water storage to 45°F using a 300 m2 roof pond. This is a heat sink which if used to provide cooling and dehumidification, will provide 576000BTU of cooling. This is the equivalent of a 3 ton unit operating 16 hours a day. It was found that a water layer thicker than 0.1 mm would radiatively isolate the selective cover, making the concept of a liquid thermal protection useless as a means of providing only convective protection. However, as a selective cover, teflon was found to make the best use of the 1-13um window. As a result, this would provide 33 BTU/ft2-might as compared to 11 BTU/ft2-night for a black cover. It was also found that a green of blue and yellow or red dye mixture, when dissolved in water, would provide a black surface throughout the visual and infrared range.
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Beck, James K.
Master of Science (M.S.)
College of Engineering
Length of Campus-only Access
Masters Thesis (Open Access)
Air conditioning -- Climatic factors, Air conditioning -- Equipment and supplies -- Design and construction
Ring, Steven Gilbert, "A Passive Cooler for a Humid Climate" (1979). Retrospective Theses and Dissertations. 442.