Numerical investigation of the thermal performance of a radiant ceiling cooling panel with segmented concave surfaces

Radiant cooling/heating (RCH) panel systems have recently received increasing attention because of their energy-efficient operation and improved comfort performance. Therefore, this study proposes a novel RCH panel with segmented concave surfaces. The new panel has the same surface area as a conventional flat surface panel. A series of laboratory tests were conducted to investigate the heat transfer characteristics inside a chamber equipped with the new panel. Moreover, a three-dimensional finite volume simulation was developed to investigate the heat transfer, fluid flow, and thermal comfort conditions inside a single room equipped with the proposed panel, and the results were compared with those of a conventional flat surface panel under the same operating conditions and cooling load. First, the curvature cord length ratio to curvature radius (L/R) was optimized in the range of 0 (flat) to 2. In all cases, the surface area was the same, but the coverage area ratio varied. In addition, the impact of different coverage area ratios from 55% to 81% and the influence of adding void spaces of 29 mm and 11 mm between adjacent curved segments were analyzed. The results showed that the simulation achieved good agreement with the experimental results with an accuracy of 98.9%. The coverage area ratio played an essential role in decreasing the indoor air temperature by 2 °C and reducing the floor temperature by 1.6 °C. When the L/R ratio changed from 0 to 1.5 at a coverage ratio of 81%, the average air temperature decreased by 1 °C. Moreover, increasing the L/R ratio from 0 to 2 with void spaces of 2.9 mm and 11 mm reduced the radiation heat transfer coefficient, hr, by 31%, while the convection heat transfer coefficient, hc, at the panel upper surface increased by 174%. Changing only the panel surface shape from flat to concave and segmented enhanced the thermal performance and thermal comfort inside the indoor environment.