Experimental study of the coupled wall system of pipe-encapsulated PCM wall and nocturnal sky radiator for self-activated heat removal

摘要

The coupled pipe-encapsulated PCM wall system with a nocturnal sky radiator is a novel type of building envelope structure for low energy buildings. It absorbs outdoor heat and stored it by using the pipe encapsulated PCM inside the wall in the daytime, and the stored heat is automatically discharged into space through the sky radiator by the effect of the gravity heat pipe at nighttime. It makes full use of the natural cooling source, which can effectively reduce indoor heat gain through the envelope and improve the utilization efficiency of PCM. In this paper, an experiment platform integrating the pipe encapsulated PCM wall module, the nocturnal radiator module, the heat pipe circulation module and measurement system together is established. The heat transfer characteristics of the wall system in four cases under the dynamic boundaries are tested, and the performances are contrastively discussed. Comparing to the wall without nocturnal radiation, the coupled wall system can well reduce the indoor cooling load and the wall internal surface temperature. The wall internal surface average heat flux can reduce 10.2 W/m(2), and the cumulative indoor heat gains can reduce 29.7%. The results show the good thermal performance and energy-saving potential of this coupled pipe-encapsulated PCM wall system with a nocturnal sky radiator. With the development of new materials for enhancing the capability of radiative cooling such as the glass-polymer hybrid metamaterial, the performance of the coupled wall system may be significantly improved when these materials are used in the sky radiators. (C) 2021 Elsevier B.V. All rights reserved.