Thermal Distribution Performance of NPCM: NaCl, NaNO₃ and KNO₃ in the Thermal Storage System

Abstract

The experiment is studied on thermal distribution in the thermal energy storage system with non-phase change materials (NPCM): NaNO 3 , KNO 3 and NaCl in the range of 25 ° C - 250 ° C . The cylindrical storage system was made of stainless steel with 25.6 cm-diameter and 26.8 cm-height that was contained of these NPCM. There was one pipe for heat transfer fluid (HTF) with 1.27 cm-diameter that manipulates in the storage tank and submerges to NPCM. The inner pipe was connected to the 2.27 cm-diameter outer HTF tube. The tube was further connected to the thermal pump, heater and load. The pump circulates the synthetic oil (Thermia oil) within the pipe for heat transferring purposes (charging and discharging). An electric heater is used as the heat source. The limitation of the charging oil temperature is maintained at 250 ° C with the flow rates in the range of 0.58 to 1.45 kg/s whereas the inlet temperature of the discharge oil is maintained at 25 ° C. Thermal performances of TES (thermal energy storage) such as charging and discharging times, radial thermal distribution, energy storage capacity and energy efficiency have been evaluated. The experimental results show that the radial thermal distribution of NaCl for TR inside, TR middle and TR outside was optimum of temperature down to NaNO 3 and KNO 3 respectively. Comparison of NPCMs with oil, flow rates for NaCl were charging and discharging heat transfer than KNO 3 and NaNO 3 . The thermal stored NaCl ranged from 5712 - 5912 J; KNO 3 ranged from 7350 - 7939 J and NaNO 3 ranged from 6623 - 6930 J respectively. The thermal energy stored for experimental results got with along the KNO 3 , NaNO 3 and NaCl respectively. The thermal energy efficiency of NaCl, KNO 3 and NaNO 3 was in the range 66% - 70%.