Experimental investigations of high-temperature shell and multi-tube latent heat storage system

High-temperature thermal energy storage (TES) systems improve the reliability and performance of solar-thermal utilization systems due to their ability to levelize the gap between the energy supply and demand. The present work focuses on conducting extensive experimental investigations to study the performance characteristics of a latent heat storage (LHS) system. A customized experimental facility was designed and developed with air as the heat transfer fluid operating at a maximum temperature of 400 degrees C. Sodium nitrate used as the phase change material (PCM) was filled in the shell side of a multi-tube heat exchanger and performance parameters such as charging/discharging time, energy stored/discharged, and output power were estimated by varying the flow rate and inlet temperature of air. The axial and radial temperature distributions reveal that the heat transfer occurs predominantly due to natural convection during the charging process, whereas, discharging takes place primarily due to conduction heat transfer in the axial direction. The energy storage of similar to 19.5 MJ was achieved with maximum PCM temperature reaching up to 365 degrees C. A comparison with cast steel and concrete based sensible heat storage (SHS) mediums operating at similar experimental conditions indicates that the LHS medium possesses high energy storage density and low storage cost, however, a combination of SHS and LHS mediums can meet the diverse load requirements in the end-user applications.