Mixed convection and entropy generation in an open cavity for thermal control applications using GO + MXene hybrid nanofluids and phase change material

Purpose The primary purpose of this study is to investigate the mixed convection and entropy generation performance of an open cavity using a combination of phase change materials (PCM), metal foam and hybrid nanofluids (HyNFs). By evaluating various cavity orientations, PCM layer thicknesses and nanoparticle concentrations under different flow conditions, the research aims to identify the optimal configuration for uniform heat distribution. Ultimately, the study seeks to provide an effective and innovative thermal control perspective for optimizing heat generation systems. Design/methodology/approach A numerical approach was used to analyze an open cavity integrating a PCM, metal foam and GO + MXene hybrid nanofluids. Computations were performed under laminar flow conditions (Re = 100 and 1,000) with a constant heat flux of 1,000 W/m² applied to all cases. The study systematically evaluated three different cavity orientations, two PCM layer thicknesses (0.2D and 0.5D), and varying nanoparticle weight concentrations (0.1, 0.2 and 0.3 Wt.%) to assess their combined effects on mixed convection, melting performance and entropy generation. Findings The results demonstrate that the vertical upper cavity orientation is optimal for uniform heat distribution, reaching steady state significantly faster (1,200 s earlier) than the horizontal setup. Notably, adding nanoparticles suppressed natural convection, which decreased melting performance. However, the highest Nusselt number (Nu) was achieved using 0.3 Wt.% hybrid nanofluid across all conditions, with the vertical upper cavity doubling the Nu compared to other configurations. In addition, maximum total entropy generation occurred in the vertical bottom cavity model (0.2D), yielding values approximately four times higher than the horizontal 0.5D model. Originality/value This paper presents a broad perspective for thermal control applications. It presents the first reported study to evaluate the performance of an open-cavity system using a GO + MXene hybrid nanofluid (HyNF) in combination with a PCM layer. A significant novelty is the use of both Nusselt number (Nu) and Entropy Generation (EnG) analysis to evaluate system efficiency. The study fills a gap in the literature by detailing how cavity orientation (Horizontal vs. Vertical) and PCM layer thickness.