Sakhail Islam Biaz, Golam Sharoar Fahim, M I Islam, Nahyan Ahnaf Pratik, Md. Hasan Ali
ABSTRACT Flat plate collector (FPC) is a solar thermal technology to use solar energy for heating in the residential and commercial sectors; however, their performance is strongly influenced by the configuration of the riser tubes, which affects both heat transfer and hydraulic losses. This study experimentally investigated thermal, hydraulic, and exergy performance while maintaining a constant absorber plate area. Type I and Type II are two spiral configurations with different tube diameters and flow path lengths and Type III is a elbow‐based square configuration. In the assessment of performance, water was used as the working fluid with flow rates of 0.4, 0.5, 0.63, and 0.8 kg/min. The results indicate that the Type II outperformed the other configurations across all operating conditions, achieving a maximum temperature rise of 5.55°C, 155.52 W heat gain, and 66.98% thermal efficiency at a flowrate of 0.4 kg/min. Hydraulic analysis indicated that Type I experienced the highest pressure drop of 570 Pa at 0.8 kg/min due to its extended flow length and smaller hydraulic diameter, while Type II exhibited the lowest pressure drop owing to its larger tube diameter and reduced flow length. Type III showed intermediate hydraulic losses, attributed to elbow‐induced minor losses associated with abrupt flow redirection. Exergy analysis further confirmed the superior thermodynamic performance of the Type II configuration, with a maximum exergy efficiency of 1.86%–1.88% at 0.4 kg/min. This study established that geometrical orientation of the riser tubes provides a key factor in increasing performance in flat‐plate solar collector designs.