Thermally stratified tanks

How tanks fail to stratify is discussed, as well as a new solar collection strategy that allows stratification to be maintained. A theory that models thermally stratified tanks reasonably well is briefly summarized. Tests of tanks fitted with various internal baffle and diffuser configurations are described. Conclusions are: the new collection strategy is essential for maintaining stratification; and most tanks can remain stratified in diurnal cycling. Dip tubes and vertical baffles degrade stratification. Tank walls should have low heat capacity compared to that of water. Tanks with a height to diameter ratio of about four provide the best stratification without excessive thermal losses. Simple inlet and outlet diffusers provide the test thermal stratification.