Experimental studies on the operating characteristics of air-layer-integrated radiant cooling units

Radiant cooling is widely acknowledged as an energy-efficient approach to indoor thermal environment regulation. It offers an improved environment in terms of thermal comfort, compared to traditional air-cooling methods, but suffers from condensation risk and insufficient cooling power in hot and humid climates. To overcome these limitations, an Air-Layer-Integrated Radiant Cooling Unit (AIRCU) was developed, which seals a layer of dry air between an infrared transparent membrane and the radiant cooling surface. This innovative approach allows the use of lower radiant cooling temperatures to increase cooling power while concurrently maintaining the membrane at a higher temperature to minimize the risk of condensation. In our previous studies, the heat transfer model of AIRCUs was established, and the feasibility of the concept was verified. However, there is a lack of research on the operating characteristics of AIRCUs. In this paper, both experimental and numerical studies are conducted to investigate the operating characteristics of the AIRCUs under diverse cooling temperatures, chilled water flow rates, and cooling loads. Results indicated that the thermal environment created by the AIRCUs was uniform, and it can be characterized by uncooled surface temperature and radiant cooling surface temperature. Under different load conditions, the chilled water supply temperature was suggested as the control variable to adjust the thermal environment. To satisfy the thermal comfort, the operative temperature should be controlled within 23.6 ℃ ∼ 26.4℃. This study provides valuable guidance on operating variable settings and environmental control of the AIRCU and promotes its application. © 2024 Elsevier Ltd.