Study of the thermal performance of sensible heat energy unit

An experimental investigation was carried out to study the thermalperformance of a sensible heat storage unit. For this purpose an experimentalset up has been designed and series of tests have been carried out. Somecommon materials for sensible heat energy storage such as soda lime spheresand river gravels were examined. A bed of 0.072 m3 size with an average voidfraction of 0.45 was tested for thermal energy storage using water as a workingfluid which was heated using electric heaters.The effect of the storage material, charging time, bed size, inlet water flowrate, input heat, and load variation on the performance of sensible heat energystorage unit represents the main system parameters.The temperature distribution at both axial and radial locations in the bedwas measured. This was made for both solid and fluid in the two cases of flow:circulating and non-circulating, for both charging and recovery modes.In the case of non-circulating flow, isothermal contour lines of the fluid aredrawn at all axial and radial sections inside the test section for the two storagematerials during charging and recovery times. This was done to demonstratethe behaviour of the fluid during the stagnation conditions.In the case of circulating flow, variation of the exit fluid temperature withcharging and recovery times at different inlet flow rates, aspect ratio, inputheat and exit flow rates (load demand) are also shown.The study showed that using river gravels is much superior for thermalenergy storage than using soda lime spheres due to their high thermalproperties. River gravels take less time for storage in comparison with so~alime spheres. A larger size of bed gives higher storage capacity for thematerials used. As the inlet flow rate increases during charging mode, moreheat is absorbed by the bed. For recovery, the time decreases as the inletwater flow rate increases. When the outlet flow rate (load demand) decreases,a higher exit water temperature is obtained. The recovery time increases as theinput heat increases.