BUOYANCY DRIVEN MASS TRANSFER IN A LIQUID DESICCANT STORAGE TANK

A new concept for long-term solar storage is based on the absorption properties of aqueous calcium chloride. Water, diluted and concentrated calcium chloride solutions are stored in a single tank. An immersed heat exchanger and stratification manifold are used to preserve long-term sorption storage, and to achieve thermal stratification. The feasibility of the concept is demonstrated via measurements of velocity, CaCl2 mass fraction, and temperature in a 1500 liter prototype tank during sensible charging. Experiments are conducted over a practical range of the relevant dimensionless parameters. For Rayleigh numbers from 3.4x10(8) to 5.6x10(10) and buoyancy ratios from 0.8 to 46.2, measured Sherwood numbers are 11 +/- 2 to 62 +/- 9 and the tank is thermally stratified. Convective mixing is inhibited by the presence of a steep density gradient at the interface between regions of differing mass fraction. The predicted storage time scales for the reported Sherwood numbers are 160 to 902 days.