Experimental comparison of the thermal indoor environment created by a radiant, and a combined radiant and convective cooling system

This study reports the results from an experimental comparison of two cooling systems. The studied systems were a radiant cooling system (radiant ceiling panels and mixing ventilation), and a combined radiant and convective cooling system (combination of a different kind of ceiling panels and diffuse ceiling ventilation). The experiments were conducted in a climate chamber under controlled conditions. Two systems were compared under the cooling loads of 36 W/m2 and 62 W/m2. Both systems kept the room temperature constant at 26°C. The combined radiant and convective cooling system was tested additionally to keep the Predicted Mean Vote (PMV) between ±0.2, which essentially corresponded to a lower room temperature since the experiments were carried out under steady-state conditions. Air temperatures, globe temperatures (operative at 0.6 m and 1.1 m heights), and air velocities were measured at different heights and at different locations in the climate chamber. Both systems created very similar and uniform thermal indoor environments and flow fields. Radiant ceiling cooling compensated for the presence of warm surfaces in the chamber, resulting in very close air and globe (operative) temperatures. It is important not to create local thermal discomfort for the occupants while trying to achieve better overall thermal comfort with a PMV control strategy. The final system selection in practice would depend on factors such as energy performance, costs (initial and operational), available space, control possibilities and so forth, since both systems created very similar thermal indoor environments.