Analysis of the rigid porous manifold as an effevtive device to stratify solar thermal storage tanks.

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Analysis of the rigid porous manifold as an effevtive device to stratify solar thermal storage tanks.

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One of the most effective and simplest methods to maintain thermal stratification of solar hot water storage tanks during charge and discharge is the use of a rigid porous manifold. The same manifold design can be employed within a novel liquid desiccant solar thermal storage tank to prevent destruction of chemically stored energy during charge and discharge. This type of manifold does not require any moving parts or special materials and thus is particularly appealing for solar thermal storage systems. It has a series of vertical hydraulic resistance elements placed within a perforated tube. At the design operating conditions, the manifold ensures that fluid entering the tank is delivered to the vertical position where it is the same density as the tank fluid. In the present study the utility of a rigid porous manifold is assessed over a range of operating conditions in both a solar hot water and liquid desiccant storage environment. The primary result is the development of a simple relationship between a dimensionless performance indicator and a second dimensionless parameter that represents the operating condition. A simulation model is used to define this relationship between the operating condition and manifold performance and is applicable to manifolds operating in both hot water and liquid desiccant storage tanks. A plug flow tank model is used to approximate transient tank stratification. Initial modeling suggests off-design operation results in low levels of mixing. Finally, a manifold was built and tested within a prototype liquid desiccant tank. Results show that the design returns low density fluid through the bottom of the tank at a significantly reduced mixing rate compared to free discharge. The same manifold design is able to return high density fluid with minimal mixing.


University of Minnesota M.S. thesis. July 2011. Major: Mechanical engineering. Advisor: Dr. Jane H. Davidson. 1 computer file (PDF); v, 73 pages, appendices A-D.

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Ghosh, Vivekananda. (2011). Analysis of the rigid porous manifold as an effevtive device to stratify solar thermal storage tanks.. Retrieved from the University Digital Conservancy,

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