Thermal characteristics of aluminium hollowed bricks filled with phase change materials: Experimental and numerical analyses

• Published in: Applied thermal engineering 2019-06, Vol.155, p.70-81
• Main Authors: Zhang, J.J., Yang, C.H., Zhang, J.S.
• Format: Article
• Language: English
• Subjects: Aluminium hollowed bricks; Aluminum; Bricks; Building materials; Computer simulation; Control systems design; Enthalpy; Experimental study; Free convection; Heating; Laminar flow; Latent heat; Latent heat absorption; Natural convection; Numerical analysis; Numerical simulation; Paraffins; Phase change materials; Porosity; Temperature control; Thermal control systems; Thermal diffusivity; Thermal management; Thermal protection; Thermal response; Variations
• ISSN: 1359-4311; 1873-5606
• DOI: 10.1016/j.applthermaleng.2019.03.103

•Thermal response for brick filled with PCMs can be divided into three periods.•Temperature control times for brick with PCMs are 2.5 times than that without PCMs.•Temperature uniformity of aluminum base is better in latent heat period.•Holes closer to the bottom of sample behave the stronger natural convection. Based on the thermal management requirements of bearing structures in the thermal protection system of aircrafts, a group of aluminium hollowed bricks with low porosity is manufactured. The thermal response characteristics of these bricks filled with 48.3–57.8 °C paraffin are experimentally studied. The results show that the infilling of PCMs may significantly retard the heat transfer through the bricks due to the large latent heat absorption, and the temperature control time is thus 2.5 times that for the case without PCMs. The samples with higher porosity have longer melting duration times and lower entire temperatures after completely melting. A higher porosity or larger hole diameter is more beneficial for the thermal control at the cold end because of the lower effective thermal diffusivity. A numerical model is also established to further analyse the field distributions of the samples. The simulation shows that the natural convection of the liquid PCMs in holes is a laminar flow. In contrast to the sensible heat period, the temperature uniformity of the aluminium base is better in the latent heat period, and the corresponding temperature fluctuation amplitudes along the centre-lines of the holes are larger. Furthermore, whether for bottom heating or top heating, the holes that are closer to the bottom of the sample have stronger natural convection. These findings can provide beneficial guidance for the design of a thermal control system with metallic hollowed geometries.