Thermally driven natural circulation water pump

Hobbs, K. ; Dobson, R. T. (2015)


ENGLISH ABSTRACT: The water utilized by passive air-conditioning systems in buildings is typically required at higher elevations. The thermally driven natural circulation water pump (TDNCWP) is a passively driven pumping system for delivering water from ground level against gravity to a higher elevation. The TDNCWP is shown by theoretical and experimental work to provide water at varied elevations using non-mechanical, passive means. Experiments were conducted on two experimental TDNCWP set-ups of different cross-sectional areas to evaluate the pump design and the theoretical model. A temperature difference of 9 to 12.5 °C between the heating and cooling sections induced 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 °C induced an average velocity of 0.25 to 0.3 m/s. An asymmetrical velocity profile was observed which varied at different points in the loop. A water delivery rate of 1.2 to 7.5 L/day was experimentally determined. This compares well to the passive air-conditioning water requirements of a small building. The theoretical model over-predicted the delivery rate at increased duct cross-sectional areas but fared 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 the TDNCWP provides an alternative to a conventional water pump for low-volume water pumping requirements.

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