Mathematical model of flat plate solar thermal collector and its validation Michał Wasik, Marcin A. Bugaj, Tomasz S. Wiśniewski, Maciej Klein, Patryk Chaja and Sebastian Bykuć E3S Web Conf., 70 (2018) 01019 Published online: 03 December 2018 DOI: 10.1051/e3sconf/20187001019