Performance analysis of a stationary parabolic trough solar collector with a flat metallic receiver incorporating paraffin wax PCM

This study evaluates the performance of a parabolic trough solar collector (PTSC) equipped with a novel flat metallic receiver designed to enhance heat transfer and storage under stationary non-tracking conditions in Sinop, T & uuml;rkiye. Two receiver configurations were fabricated and experimentally tested: one with paraffin wax (PW) integrated as a phase change material (PCM) and one without PW. The experimental study was conducted in two stages. In the first stage, the influence of mass flow rate on system performance was examined under high (HF), medium (MF), and low (LF) flow conditions. The average thermal efficiencies of the receiver with PW were 37.85%, 35.27%, and 27.55% for HF, MF, and LF, respectively, while the receiver without PW achieved 38.97%, 29.82%, and 19.36%. Increasing the mass flow rate enhanced thermal efficiency in both configurations; however, this effect was considerably more pronounced for the receiver without PW, where the HF efficiency exceeded the MF and LF cases by 30.7% and 101.1%, respectively. For the PW-integrated receiver, the corresponding improvements were limited to 7.3% and 37.3%, indicating a stabilizing effect of latent heat storage. Based on these findings, the HF condition was identified as the optimum operating regime and selected for the second experimental stage. In this stage, the thermal storage performance of the two receivers was directly compared at the same HF rate. The results showed that the PW-integrated receiver achieved 16.6% higher thermal efficiency and 47% higher exergy efficiency than the receiver without PW. Moreover, the latent heat release provided by PW significantly improved temperature stability and system performance during periods of declining solar radiation. Overall, the proposed paraffin-wax-integrated design represents an effective approach for enhancing PTSC performance under stationary operating conditions without requiring complex system modifications. Although long-term cycling tests were not performed, paraffin wax was selected due to its well-documented thermal reliability in previous studies. The reported results are based on a comparative experimental evaluation conducted under real outdoor operating conditions and are intended to highlight the relative performance differences between the two receiver configurations; long-term PCM stability, detailed economic analysis, and optical optimization are beyond the scope of the present study.