The objective of the present work is to investigate experimentally the thermal behavior of a packed
bed of combined sensible and latent heat thermal energy storage (TES) unit. A TES unit is designed,
constructed and integrated with constant temperature bath/solar collector to study the performance
of the storage unit. The TES unit contains paraffin as phase change material (PCM) filled in spherical
capsules, which are packed in an insulated cylindrical storage tank. The water used as heat transfer
fluid (HTF) to transfer heat from the constant temperature bath/solar collector to the TES tank also
acts as sensible heat storage (SHS) material. Charging experiments are carried out at constant and
varying (solar energy) inlet fluid temperatures to examine the effects of inlet fluid temperature and
flow rate of HTF on the performance of the storage unit. Discharging experiments are carried out by
both continuous and batchwise processes to recover the stored heat. The significance of time wise
variation of HTF and PCM temperatures during charging and discharging processes is discussed in
detail and the performance parameters such as instantaneous heat stored and cumulative heat stored
are also studied. The performance of the present system is compared with that of the conventional
SHS system. It is found from the discharging experiments that the combined storage system
employing batchwise discharging of hot water from the TES tank is best suited for applications
where the requirement is intermittent.
r 2006 Elsevier Ltd. All rights reserved.