Investigating the effects of nano-enhanced phase change material on melting performance of LHTES with novel perforated hybrid stair fins

Abstract

The unique features of LHTES have led researchers to seek ways to resolve its main deficiency, namely low heat transfer parameters. Accordingly, the present study aims to improve these parameters by: (1) introducing new geometries and arrangements of extended surfaces (upward, downward, and hybrid stair fins), (2) implementing perforations, and (3) using nano-enhanced PCM with different liquid fraction of CuO nanoparticles (0.5, 1.0, and 1.5 %) along with the selected geometry. This is achieved by discretizing the 3D and unsteady state governing equations based on collocated grids and the finite volume method. Moreover, the well-established enthalpy-porosity method is used to model the melting process. The numerical method has been proven to predict melting processes accurately in various numerical tests. Based on the results, it is determined that all the considered ideas improved the melting parameters by varying amounts. Melting performance parameters in the most efficient case, LHTES equipped with perforated hybrid USD fins with nano-enhanced PCM (1.5 % CuO-Lauric acid), are improved compared to the reference case by 178, 208, and 141 % in terms of Nusselt number, PCM charging power, and total stored energy, respectively. Compared to the previously designed LHTES, these enhancements result in a 66 % reduction in melting time.