Natural convection heat transfer in isosceles prismatic roof with perforated partition and phase change material

Abstract

In this work, both numerical and experimental studies are conducted to predict the natural convection heat transfer characteristics in the isosceles prismatic roof with the perforated partition and phase change material. This study can provide energy-saving methods for the design of passive buildings, responding to the increasingly tense energy crisis. Through post-processing, the effects of tilt angle (θ=30°and45°), partition perforation size (φp=0.014mand0.024m), and volume of paraffin (Vpcm=0m3and1.1×10-4m3) on the flow field inside the triangular cavity were investigated. The CFD results of different turbulence models are compared with the measured temperature data to achieve the most suitable turbulence model. By comparing the heat transfer coefficient calculated by the empirical formula with the numerical results of various turbulent models, it can be found that the error of the zero equation model is the smallest. The root mean square error (RMSE) between the numerical and the experimental results is only 0.6 %, so this turbulent flow model is used for the subsequent analysis in this study. The results also showed that the heat convection coefficient of the large inclination angle is about 10 % higher than that of the small inclination angle, and the velocity of the flow at the top of the partition is significantly improved, and the convection effect is better. The perforation of the partition forms the chimney effect and causes obvious updraft. The heat transfer from the air to the PCM is not as expected, and the effectiveness of the PCM is minimal.