Performance comparison of medium temperature domestic packed bed latent heat storage systems

Thermal performances of three packed bed latent heat medium temperature thermal energy (TES) storage systems are evaluated during charging and discharging cycles at low (4 mL s(-1)), medium (6 mL s(-1)) and high (8 mL s(-1)) flow-rates. The three phase change materials (PCMs) used in the storage systems are adipic acid, erythritol and eutectic solder (Sn63Pb67). Each TES tank comprises of a packed bed of 40 similar aluminium spherical capsules with the three different PCMs inside each tank. The thermal performance of these systems is evaluated in terms of the temperature profiles, total energy, total exergy, useful energy and useful exergy, during charging and discharging. Erythritol did not undergo phase transition during discharging at all the flow-rates due to super-cooling. The erythritol TES system shows the greatest efficiencies with regards to all the performance parameters considered with an overall energy efficiency of about 39.1%. The efficiencies of all the TES systems generally decreased with an increase in the heat transfer fluid (HTF) flow-rate. Although the eutetic solder TES stored and discharged greater quantities of energy at all the flow-rates, its performance was reduced by the lower degree of thermal stratification in the tank and longer charging and discharging times. (C) 2019 Elsevier Ltd. All rights reserved.