Thermal environment and thermal comfort built by decoupled radiant cooling units with low radiant cooling temperature

Abstract

A decoupled radiant cooling unit (DRCU), which uses an infrared-transparent and conductive resistant (ItCr) layer to cover the radiant cooling surface and prevent it from contacting with air, reduces the condensation risk and simultaneously increases the cooling capacity. The cooling capacity could be enhanced using a low radiant cooling temperature (e.g., <15.0 °C), which is lower than conventional cooling capacity (e.g., 18.3 °C). However, one interesting problem under low radiant cooling temperatures is whether the thermal environment and thermal comfort built by the DRCU will be significantly affected. The present study developed a computational fluid dynamic model to investigate the thermal environment created by a DRCU inside a small chamber. Four cases with the radiant cooling temperatures of 18.3 °C, 14.7 °C, 9.5 °C and −2.3 °C and radiant cooling areas of 9.0 m2, 7.2 m2, 5.4 m2 and 3.6 m2 were investigated. The thermal environment was evaluated using temperature and velocity distributions, and the thermal comfort was evaluated through predicted mean vote (PMV), predicted percentage dissatisfied (PPD) and percentage dissatisfied (PD). The results indicated that the thermal environment and thermal comfort created by the DRCU under low radiant cooling temperatures satisfied the comfort criteria of the ASHRAE Standard.