Numerical analysis of performance enhancement in a shell and double-coil heat exchanger using three passive flow and heat transfer methodsZakarya Ahmed, Waqid Al-Mussawi, Pooya Ghodratallah, Abdellatif M. Sadeq, Shaymaa Abed Hussein, Husam Rajab and Borhen LouhichiEur. Phys. J. Plus, 140 6 (2025) 567DOI: https://doi.org/10.1140/epjp/s13360-025-06496-6