Experimental study on optical properties of various paraffin-based PCM glazing unit and radiative transfer model optimization

Integrating phase change material (PCM) into glazing units can lead to the ability of dynamic response to solar radiation and enhance thermal mass. In order to clarify the optical performance of phase change material glazing unit (PCMGU) during the dynamic response stage, this study analyzes the variations of transmittance and reflectance of PCMGUs filled with different paraffins during phase change process, by using a spectrophotometer and a temperature measurement device. Additionally, the impact of the paraffin cooling rate on this process was also examined. The experimental results indicate that: (1) During the solid-liquid phase change process, the curve of PCMGU transmittance and reflectance versus paraffin temperature exhibits a significant linear characteristic, with 75–93 % of transmittance and reflectance changes appearing during this stage; (2) Adjusting the paraffin cooling rate does not alter this linear characteristic; (3) Approximately 19 % and 36 % of PCMGU transmittance and reflectance changes occur during the solid-solid phase change process, respectively. Finally, based on the experimental patterns, the radiative transfer model for PCMGU was optimized, reducing its calculation error to a range of 0.17–0.92 times that of previous models (in terms of root mean square error).