Abstract
Experimental thermal stratification evaluation of a packed bed latent heat storage is done during charging cycles. The packed bed latent heat storage system consists of adipic acid encapsulated in aluminum spheres. Sunflower oil is used as the heat transfer fluid during charging cycles. Stratification number profiles are used to evaluate thermal stratification in the storage system. Charging experiments are carried out with three different flow-rates (4 ml/s, 8 ml/s and 12 ml/s). Charging experiments are also done using the same flow-rate (8 ml/s) with three different set heater temperatures (220 °C, 240 °C and 260 °C). The lowest charging flow-rate (4 ml/s) shows the best variation of the stratification number profile since it shows the least drop from the peak value and the shortest charging interval. Different set heater temperatures show almost identical stratification number profiles. The effect of the charging flow-rate is more significant than the effect of the charging set heater temperature when evaluating thermal stratification for this particular system.
Highlights
The charging efficiency of thermal energy storage (TES) tanks is enhanced by thermal stratification
Limited recent studies have been reported on thermal performance and stratification for medium temperature applications using thermal oils [6,7,8,9,10], it necessary to carry out this study to understand the efficiency of these systems
The aim of this paper is to evaluate the charging stratification performance a Sunflower oil based packed bed latent heat storage system using adipic acid encapsulated in aluminum spheres
Summary
The charging efficiency of thermal energy storage (TES) tanks is enhanced by thermal stratification. A thermal gradient exists between the top and the bottom of the storage tank. The region between these two regions in liquid based TES systems known as thermocline should be kept at a minimal possible thickness for increased efficiency of the systems. Studies on thermal stratification have been predominantly on water storage for domestic hot water systems [1,2,3,4,5]. For higher medium temperature applications (100 oC to 300 oC), the hot water storage tank is not suitable since water has to be pressurized for these applications making storage tank design complicated. Limited recent studies have been reported on thermal performance and stratification for medium temperature applications using thermal oils [6,7,8,9,10], it necessary to carry out this study to understand the efficiency of these systems
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