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Effect of Diffuser Height on Thermocline in Stratified Chilled Water Storage Tank
Author(s): Firas Hassan, Maathe Theeb
Keywords: cool thermal energy storage; stratification; thermal performance; diffuser height; inlet diffuser.
Chilled water energy storage using thermal stratification technique currently used in the vast area because it contributes to reducing energy consumption and refrigeration capacity as well as low maintenance, operating and capital costs. In this paper, experimental tests were carried out on a small-scale vertical cylindrical storage tank equipped with an elbow-type conventional diffuser at inlet heights of 20, 170, 320 and 470mm for flow charging rates from 1.5-7.5l/min. for obtaining a good thermal separation. The degree of stratification was estimated by means of temperature distributions and performance metrics which involve thermocline thickness, the half-cycle figure of merit and equivalent lost tank height. The results show that the decrease in diffuser height above the tank floor tends to the steep thermocline or satisfactory thermal separation, the stratification and thermal performance were obtained at diffuser height of 20 mm within the limiting volume flow rates 1.5-4.5 l/min. better than those at volume flow rates ranging from 5.5-7.5l/min. and much better than at diffuser heights of 170, 320 and 470mm for various flow rates.