Thermal comfort investigation of membrane-assisted radiant cooling in outdoor settings

• Published in: Sustainable cities and society Vol. 113; p. 105634
• Main Authors: Yang, Junran, Liang, Yan, Zhong, Ziwen, Dharmasastha, K., Xie, Yongxin, Niu, Jian-Lei
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15-10-2024
• Subjects: Local radiant cooling; Outdoor thermal comfort; Thermal comfort votes; Thermal sensation votes; Urban microclimate; Thermal sensation votes; Urban microclimate; Local radiant cooling; Outdoor thermal comfort; Thermal comfort votes
• ISSN: 2210-6707
• DOI: 10.1016/j.scs.2024.105634

•Local cooling is created outdoors by membrane-assisted radiant cooling panels.•Asymmetric radiant cooling helps offset thermal sensation to neutral zone.•The highest coolness appears in the body parts directly facing cooling surface.•Overall and local thermal sensation compared with UC Berkeley thermal comfort model.
The global warming and urban heat island effect call for mitigation strategies for improving thermal environments in open urban spaces. Radiant cooling can remove heat from the human body via direct thermal radiation, thereby creating the possibility to provide active cooling for people in outdoor environments. While using a transparent membrane, convection energy lost to the ambient airflow can be minimized. However, current research on the thermal comfort of radiant cooling systems is restricted to indoor applications, while outdoor applications remain unclear. To address this need, the study investigated the effect of membrane-assisted asymmetric radiant cooling on people's thermal perception in outdoor environments. A radiant cooling facility in an outdoor setting was built, and its cooling effects were assessed by using 248 human subjects across hot and transitional seasons. It is found that the radiant cooling facility can lower the mean thermal sensation vote (MTSV) by 0.6 to 1.5 units. The degree of cooling depends both on the panel temperature and environmental conditions. At the panel surface temperature of 14.3°C, MTSV was at the neutral zone (-0.5 ≤ MTSV ≤ 0.5) with the environmental UTCI as high as 38.1°C, whereas the thermal sensation of the group without radiant cooling was rated warm to hot. Under this condition, the ambient UTCI scope of no heat stress can be extended by 10.1°C higher. The strongest local cooling sensation appeared in the back, with an average decrease of 1.33 units in MTSV, contributing to lowering the overall thermal sensation of the body. For the first time, it is demonstrated that membrane-assisted radiant cooling panels can effectively improve thermal comfort in open outdoor settings.