Stratification Enhancement in Liquid Thermal Storage Tanks

Abstract

Abstract P gains may be realized in solar energy systems using sensible heat storage in water if thermal stratification can be promoted in the storage tank . J The degree to which stratification can be achieved and maintained in a well-insulated tank designed for a diurnal cycle will depend most strongly on the way in which the hot water from the collector and the cool water returning from the load are introduced into the tank. In applications in which the return water is maintained at or beyond the storage temperature extremes (collector water at least as hot as the warmest storage water and makeup water at least as cold as the coolest storage water) inlets of conventional design may provide good stratification. In general, however, these conditions will not be realized. The collector water temperature may, for example, be modulated due to an intermittent cloud cover. The load return temperature may vary with the load supply temperature and, consequently, may be well above the minimum tank temperature. Inlet manifolds are described in this paper which act to preserve stratification in a tank subjected to variable inlet temperature conditions. The performance of these manifolds is contrasted with that of conventional inlets subjected to the same experimental conditions.