Abstract

The parabolic trough collector (PTC) solar thermal air heater has become increasingly important in various applications due to its ability to achieve higher solar concentration, reduced heat loss, and improved efficiency. However, fluctuations in solar radiation and lower heat transfer rates can limit the overall performance of solar air heaters. The current research main objectives are overcome the above difficulties and investigates the thermal performance of PTC based solar heater configured with 80:20 ratios of hybrid nanofluid (CNT: copper oxide) and excessive heat energy stored and utilized by different ratios of palmitic: stearic acid (PA:SA) phase change material (PCM). To analysis the different PA:SA ratios on heat storage and charging/discharging behaviour, and the combined action of hybrid nanofluid and PCM on air temperature, heat transfer rate, pressure drop, and overall thermal efficiency behaviour is studied. The experimental results demonstrate significant improvements in thermal performance, and the system functioned with 50:50 ratios of PA:SA with 0.1 % concentration of hybrid nanofluid (CNT: CuO), showing the highest air temperature (79.3 ± 3 °C), enhanced heat transfer rate (877.1 ± 26 W), better heat storage capacity (1350 ± 40 kJ/kg), marginal enhancement in pressure drop (67 ± 1 Pa), and optimum thermal efficiency (63.1 ± 1 %). These findings confirm that the combined use of hybrid nanofluids and optimized PCMs can significantly enhance heat transfer, energy storage, and thermal efficiency, making it a promising approach for improving solar thermal collector performance. © 2025 Elsevier Ltd