Enhancing the Thermal Performance of a Central Tower Tubular Solar Receiver With Direct Steam Generation by Using Internal Fins and Thicknesses Variation

Abstract This study provides a comprehensive analysis of the thermal behavior of tubular solar receivers used for direct steam generation, focusing on the effects of different wall thicknesses and longitudinal rectangular fins on the internal surface. The study evaluated six tubes, including two tubes with distinct wall thicknesses (5 mm and 3 mm) without fins and four tubes with fins but varying configurations. These tubes represent external tubular receivers used in solar central tower plants and operate at 4.5 MPa with a nonuniform solar flux averaging 0.8 MW/m2. Adding longitudinal fins to the tubes significantly reduced the maximum temperature on the irradiated surface and improved heat transfer to the fluid. The study concluded that the 45F5 receiver, which has three fins on the internal section, outperforms the other receivers, presenting a higher vapor generation. Furthermore, the 45F5 geometry enhances heat transfer, allowing the lowest maximum Biot number. These results are crucial for designing tubular solar receivers with direct steam generation systems and improving their efficiency in generating energy from renewable sources.