Qianjun Mao

Bio: Qianjun Mao is an academic researcher from Wuhan University of Science and Technology. The author has contributed to research in topics: Storage tank & Thermal energy storage. The author has an hindex of 1, co-authored 1 publications receiving 43 citations.

A review on container geometry and orientations of phase change materials for solar thermal systems

Abstract: Phase change materials (PCM) are employed to store thermal energy in solar collectors, heat pumps, heat recovery, hot and cold storage. PCMs are encapsulated primarily in shell-and-tube, cylindrical, triplex-tube, spherical, rectangular, and trapezoidal containers. This review focuses on PCM's melting and solidification in different container geometries and their orientations for heat storage in solar thermal systems. The thermal storage performance of PCM depends upon fins, nanoparticle addition, container geometry, and orientations. The operating parameters such as heat transfer fluid temperature, flow rate, and initial temperature of storage material play a dominant role in PCM melting. The use of fins and nanoparticles in the shell-and-tube containers increase the melting rate to 71 and 62.6%, whereas the change in container orientation improved the melting rate up to 47.5%. The addition of fins increases the melting rate significantly, followed by nanoparticles and the container's orientation. The variation of the container's geometry and its orientation improves PCM melting passively. Container materials are preferably stainless steel and aluminum for organic and inorganic PCMs to avoid corrosion. PCM container geometry and orientations are practical passive heat transfer enhancement techniques in the long-term compared to adding nanoparticles and attaching fins. This review focuses on significant aspects of PCM container designs for practical solar thermal storage.

Optical properties and cooling performance analyses of single-layer radiative cooling coating with mixture of TiO2 particles and SiO2 particles

Abstract: Radiative cooling can achieve cooling effect without consuming any energy by delivering energy into outer space (3 K) through “atmospheric window” (8–13 μm) Conventional radiative cooling coating with multi-layer structure was severely restricted during application due to its complex preparation process and high cost In this study, a single-layer radiative cooling coating with mixture of TiO2 particles and SiO2 particles was proposed The algorithm for calculating the radiative properties of the multi-particle system was developed Monte Carlo ray-tracing method combined with that algorithm was used to solve the radiative transfer equation (RTE) of the single-layer radiative cooling coating with mixture of TiO2 particles and SiO2 particles The effects of particle diameter, volume fraction and coating thickness on radiative cooling performance were analyzed to obtain the best radiative cooling performance The numerical results indicated that the average reflectivity of the single-layer radiative cooling coating with mixture of TiO2 particles and SiO2 particles in the solar spectrum can reach 956%, while and the average emissivity in the “atmospheric window” spectrum can reach 949% without additional silver-reflectance layer The average reflectivity in the solar spectrum and average emissivity in the “atmospheric window” spectrum of the single-layer radiative cooling coating with mixture of TiO2 particles and SiO2 particles can increase 46% and 48% compared to the double-layer radiative cooling coating This numerical research results can provide a theoretical guidance for design and optimization of single-layer radiative cooling coatings containing mixed nanoparticles