Optimizing Solar Parabolic Trough Receivers with External Fins: An Experimental Study on Enhancing Heat Transfer and Thermal Efficiency

Several researchers have shown that the heat transfer performance of solar parabolic trough (SPT) receivers may be improved by increasing their surface area or by adding internal fins to the tubes. Unfortunately, the manufacture of internally finned tubes involves complex processes, resulting in significant cost increases. On the other hand, the addition of external fins to tubes is more technically and economically feasible in a low-resource setting. This study investigates the potential benefits of integrating external fins on the receiver tubes of a low-cost SPT collector system. Experiments were conducted using an SPT system with a focal length of 300 mm and a collector length of 5.1 m, and they were positioned by an automated Sun tracking system. Tests were undertaken using both smooth and externally finned receiver tubes operating at five different water flow rates. The solar receiver with a finned tube was able to provide a maximum water temperature of 59.34 degrees C compared with that of 56.52 degrees C for a smooth tube at a flow rate of 0.5 L per minute. The externally finned absorber tube was also found to have a maximum efficiency of 18.20% at an average daily solar intensity of 834.61 W/m2, which is approximately 48% more efficient than the smooth tube. The calculations indicate that the experimental SPT system using finned tubes potentially avoids 0.2726 metric tons of CO2e per year, with finned tubes outperforming smooth tubes by up to 44%. The results show that using externally finned receiver tubes can significantly enhance the thermal performance of SPT collector systems.