Experimental an‎d Numerical Analysis of Energy Absorption Enhancement in Parabolic Trough Solar Collectors

11/2/2025 12:00:00 AM

Parabolic trough solar collectors are among the most efficient technologies for concentrating solar energy. Improving the performance of these systems through the use of nanofluids, geometric modification of components, an‎d the application of porous materials has been the focus of many recent studies. In this dissertation, three complementary approaches were employed to enhance thermal efficiency, including experimental direct absorption using porous copper foams, the application of mono an‎d hybrid nanofluids, an‎d numerical indirect absorption simulation combined with exergoeconomic analysis. In the experimental part, four copper foam thicknesses (25%, 50%, 75%, an‎d 100% of the inner tube radius) an‎d two gradient foams with radially varying porosity in full-porous an‎d semi-porous configurations were examined. The highest thermal efficiency enhancement, 143.9%, was obtained for the fully porous 100% configuration, achieving an efficiency of 51.35% at an inlet temperature of 20 °C an‎d a flow rate of 120 liters per hour. The optimal configuration was the 25% copper foam with a performance eva‎luation criterion of 1.42. The gradient foam also exhibited a thermal efficiency of 50.3% an‎d a lower pressure dro‎p compared with the 100% foam, resulting in better overall performance. In the second part, titanium dioxide, multi-walled carbon nanotube, an‎d hybrid nanofluids with concentrations of 0.01%, 0.03%, an‎d 0.05% were synthesized an‎d eva‎luated in terms of stability, optical absorption, an‎d thermal conductivity. The results showed that optical absorption had the dominant contribution of 78.73% in improving efficiency. The hybrid nanofluid achieved a thermal efficiency of 49.68% an‎d a performance eva‎luation criterion up to 2.5, enabling a reduction in collector size by 55.8% an‎d in the levelized cost of energy by 55.09%. In the numerical indirect absorption analysis, an innovative receiver with a gradient porous ring an‎d hybrid nanofluid was simulated using OpenFOAM. The results indicated that the porous ring tripled the Nusselt number an‎d increased the thermal an‎d exergy efficiencies by up to 17.3% an‎d 18.5%, respectively. The exergoeconomic analysis also showed an increase in net profit by up to 30.3% an‎d a decrease in total cost per unit heat load by 7.39%.

كلكتور سهموي خطي , فوم مسي , گراديان تخلخل , نانوسيال هيبريدي , راندمان حرارتي , اگزرژي‌-اقتصادي

Parabolic Trough Collector , Porous Foam , Porosity Gradient , Hybrid Nanofluid , Thermal Efficiency , Exergoeconomic

Iman Shahdad

Mahdi Moghimi, Mahdi Navidbakhsh