Thermally driven natural circulation water pump

[摘要] ENGLISH ABSTRACT: The water utilized by passive air-conditioning systems in buildings is typicallyrequired at higher elevations. The thermally driven natural circulation water pump(TDNCWP) is a passively driven pumping system for delivering water fromground level against gravity to a higher elevation. It consists of a humid air closedduct loop to which a temperature difference is applied, resulting in a densitygradient driven flow. A hot water evaporation tray inside the loop at ground levelintroduces water vapour to the loop air flow, and a cold condensation plate insidethe loop at the elevated level removes this water vapour for passive airconditioningusage. In this thesis, a one-dimensional theoretical and numericalsimulation model is developed. Experiments were conducted on two experimentalTDNCWP set-ups of different cross sectional areas to evaluate the pump designand the theoretical model.It is shown in this thesis that the TDNCWP can provide water at varied elevationsusing non-mechanical, passive means. A temperature difference of 9 to 12.5 °Cinduced an average velocity of 0.4 to 0.6 m/s for a duct cross section of 100 mm2.For a larger cross section of 400 mm2, a temperature difference of 2 to 5 °Cinduced an average velocity of 0.25 to 0.3 m/s. An asymmetrical velocity profilewas observed which varied at different points in the loop. A water delivery rate of1.2 to 7.5 L/day was experimentally determined which compares well to thepassive air-conditioning water requirements of a small building. The theoreticalmodel over-predicted the delivery rate at increased duct cross sectional areas butfared well when compared to the smaller experimental model results.Further refinement of the numerical model and the TDNCWP design is required,and recommendations were made regarding this. It is clear however that theTDNCWP provides an alternative to a conventional water pump for low-volumewater pumping requirements.

[发布机构] Stellenbosch University