Parametric Analysis of Heat Transfer Fluid Effects on Thermal Stratification in a Latent Heat Energy Storage System

Thermal stratification significantly affects the performance of thermal energy storage (TES) systems, especially in domestic hot water (DHW) applications. While stratification in sensible heat storage is well studied, its optimization in phase change material (PCM)‐based systems has received less attention. This article examines the effects of heat transfer fluid (HTF) inlet temperature and flow rate on stratification and energy performance in a PCM‐based TES tank. Experiments are conducted at flow rates of 200, 300, and 400 LPH with inlet temperatures of 70 and 75 °C. Higher inlet temperatures reduce PCM charging time by 31.03%, 36.00%, and 36.84% for the respective flow rates. Stratification, measured by the MIX number, improves with higher flow rates and temperatures, as shown by lower values. Elevated HTF temperatures increase the temperature gradient, enhancing sensible heating and raising average storage temperature during PCM melting. The Richardson number rose initially but declined rapidly as melting reduced the thermal gradient. After melting, charging efficiency decreases due to weakened stratification. These findings emphasize the importance of controlling HTF operating conditions to enhance stratification and TES efficiency, supporting the development of advanced control strategies and designs for PCM‐based TES in DHW and renewable energy applications.