Parametric analysis of the phase change material wall combining with micro-channel heat pipe and sky radiative cooling technology

Abstract To address the problem of heat removal by phase change material (PCM) wall at nighttime in the summer season, a new cooling wall that makes use of the high latent heats of PCMs, the high heat conductivities of micro-channel heat pipes (MHPs), and the passive cooling of sky radiative cooling (RC) is introduced, and is named the MHP-RC-PCM wall. In this study, preliminary experiments were first conducted to determine the emissivity of the radiative plate and the properties of PCMs (paraffin, RT28HC). Next, numerical models of the MHP-RC-PCM wall were established to simulate the thermal behavior, and the model was validated with the experimental results. The parameters that affect the thermal behavior of the MHP-RC-PCM wall, including the phase transition temperature, latent heat of the PCM, number of MHPs, and year-round thermal behavior were investigated. The results showed that the phase transition temperature (Tm) of the PCM had a significant influence on the interior surface temperature, liquid fraction and cooling load reduction ratio of the MHP-RC-PCM wall, whereas the PCM latent heat had little effect. The cooling load reduction ratio was approximately 4% for Tm = 31 °C, which was higher than that for Tm = 26 °C. In addition, it was determined that the year-round energy-saving of the MHP-RC-PCM wall were approximately 18.2% greater than that of the Brick wall with the same thickness, and 0.4% higher than that of PCM wall in Guangzhou City, China.