Hilal, F. and Hassen, A. 2026. Estimating the Solar Fraction of a Closed Solar Water Heating System Using the Utilizability F-Chart Method under Various Operating Conditions. Wasit Journal of Engineering Sciences. 14, 1 (Mar. 2026), 1–14. DOI:https://doi.org/10.31185/wjes.Vol14.Iss1.645.