Heat Energy Transfer Using Butyl Stearate as Phase Change Material for Free-Cooling Applications

Abstract

Buildings exploit 4% of the total annual global energy consumption and account for 33% of the greenhouse gas (GHG) emissions around the world. A significant portion of this energy is consumed in buildings for heating, cooling, and air-conditioning purposes. Phase change materials (PCMs) can be used as cold accumulators for nighttime ventilation of buildings, also termed the “free-cooling concept.” An experimental test setup was established in the Laboratory for Advanced Energy Materials at US-Pakistan Center for Advanced Studies in Energy (USPCAS-E) for investigating heat transfer during charging and discharging using butyl stearate as PCM for free-cooling application. Effects of airflow rate and different metal additions on PCM charging and discharging were also assessed. Analysis of the data indicated that the increased airflow cuts the PCM charging time but reduces the time for useful cold availability. The addition of metals like aluminum (Al) and copper (Cu) powders to the PCM enhances the heat transfer rate during the charging process by 25 and 15%, respectively. Variation in size of the metal particles reveals that finer the metal size, more it enhances the heat transfer rate of the PCM during the charging process. The results and performance characteristics of the PCM show that it will be suitable for free-cooling applications.