Turning points emerging in the effect of thermal conductivity of phase change materials on utilization rate of latent heat in buildings

Nowadays, thermal conductivity as a key parameter affecting the thermal performance of PCM has attracted much attention. However, the thermal performance evaluation of ultra-high thermal conductivity PCM is scarce, especially in field of building energy conservation. Therefore, we traversed the range of thermal conductivity that can be prepared at present and within the expected time frame, which is 0.08-49.28 W.m(-1)K(-1). In addition, a novel index, Utilization Rate of Latent Heat (URLH), was proposed to evaluate matching degree between PCM and a certain application background in buildings, so as to explore the reason of poor energy-saving effect of PCM under some application backgrounds. We found that the thermal conductivity of PCM is not the higher the better in buildings, in other words, a turning point appears. The optimal thermal conductivity is about 0.6 W.m(-1)K(-1) and when the value is lower than 0.3 W.m(-1)K(-1), URLH is equal to 0 in the cases of Shanghai. Therefore, we recommend PCM re-searchers to evaluate the URLH before using PCM to avoid the ineffective use of materials. Through the analysis of URLH, researchers can know the specific parameters that affect the thermal performance of PCM and obtain the way to optimize them. (C) 2021 Elsevier Ltd. All rights reserved.