Abstract

Solar thermal heat ventilation and air-conditioning (HVAC) systems featuring parabolic trough collectors (PTCs) were found to have high efficiency at medium temperatures, be eco-friendly, and offer long-term operation. However, it found the challenges to the thermal performance of the system to be varied, depending on the availability of solar energy and the low heat transfer coefficient. This research on solar thermal collectors configured with PTC, whose thermal performance is enriched by the adaptations of myristic acid phase change material (PCM) and different volume fraction hybrid nanofluid composed by 2:1 ratios of iron oxide (Fe3O4) and copper nanoparticles via an ultrasonication process. The effectiveness of PCM and varying volume concentrations of hybrid nanofluid, both with and without a heat recovery system, on the thermal performance and melting-solidification time of a solar thermal PTC system is evaluated. The investigation results are compared to those of the system operated with water fluid without a heat recovery system. The solar thermal PTC system featured with myristic acid as a PCM/1.5 vol% hybrid nanofluid, along with a heat recovery system, has demonstrated exceptional thermal performance and achieved a thermal conductivity of 0.86 W/m·K, a specific heat capacity of 3690 J/kg·K, an enhanced heat transfer coefficient of 357 W/m2·K, and an improved latent heat of fusion of 302 kJ/kg. The integration of a heat recovery system further improved energy distribution, ensuring better heat absorption and prolonged thermal retention. These findings highlight the potential of a hybrid nanofluid with PCM in enhancing heat transfer and thermal energy storage for efficient HVAC applications. © 2025 Elsevier Ltd