Experimental investigation of natural convection near a wall containing phase change material

• We measured natural convection characteristics along Phase Change Material panels.
• There is a stationary regime before the phase change effect.
• The phase change effect contains two dynamic stages and one wall temperature slowdown/retrogression event.
• The increase of the heat transfer coefficient during the dynamic stages is expressed as function of the PCM properties.
• The wall temperature slowdown/retrogression arise many questions about the plate thermal properties.

An experimental investigation is conducted to characterize the natural convection heat transfer along panels which contain phase change materials (PCM). A dedicated configuration has been defined for this study. In this configuration, the natural convection heat transfer is triggered by a temperature scan in the ambient air. The temperature scan is responsible for the energy storage and release in the PCM panels. The corresponding experimental set-up was built and several melting and solidification tests were performed, with different values of the ambient temperature scan speed. The tested PCM panel is the Energain®wallboard by DuPont™. The system first reaches a stationary regime when the PCM is fully solid or liquid. During the stationary regime, the wall to air temperature difference and the convection heat flux are constant. The phase change causes an increase of these quantities. It is characterized by a first dynamic stage, a wall temperature slowdown/retrogression process, and a second dynamic stage. The two dynamic stages are well correlated to the PCM thermal characteristics. However, the temperature slowdown/retrogression phenomenon is unexpected. It consists in an extreme slowdown of the wall surface temperature evolution, which turns into a retrogression during the solidification experiments. The temperature slowdown/retrogression has never been observed before with PCM wallboards.