Experimental investigations on the thermal behavior of phase change material (PCM) in ventilated slabs

Experiments were conducted using a small wind tunnel to identify the thermal behavior during energy charging processes of phase change material (PCM) in rectangular slabs. A commercially available paraffin-based PCM with a nominal melting temperature range of 26-28 degrees C was encapsulated in high-density polyethylene (HDPE) slabs for thermal storage applications in buildings. The influence of air temperature and velocity as well as the slab inclination angle was evaluated using melting time and energy charging speed. The melting time was 18.8-50.8% shorter at top zone than it at bottom zone of the slabs because of the natural convection. The average energy charging speed increased from 36.3 W to 109.4 W by 201.7% when the inlet air temperature increased from 35 degrees C to 55 degrees C. However, it was slightly enhanced by 8.7% when the air velocity increased from 4 m/s to 5 m/s. The aspect ratio should be considered when studying the impact of inclination angle on energy charging process. The maximum energy storage capacity was 97.2 Wh with a fraction of 20.2% sensible heat with an energy charging speed of 109.4 W when the inlet air temperature was 55 degrees C, the air velocity was 3 m/s, and the inclination angle was 90 degrees.