The PhD thesis of researcher Mohammed Qasim Abdul Hasan was discussed at the College of Engineering, University of Basra, titled Numerical Study of Heat Transfer in a Vessel-Impeller Mixer with Flexible Baffles includes The study investigated heat exchange within tube bundles placed inside a vessel with a rotating frame, both with and without flexible baffles. Several flexible baffles are positioned inside the vessel’s circumference. The rotating frame transforms free convection into mixed convection, featuring hot and cold tubes placed throughout the vessel, with the rotating frame centrally located. Key variables studied include tube size (r*), number of tubes (Nht = Nct = 1–4), and the tubes’ radial position (e*), as well as their interactions with rotational velocities (ω* = 0–400) and Rayleigh numbers (Ra = 10³–10⁵). The results indicate that the Nusselt number increases substantially with an increase in both rotational speed and Rayleigh number, influenced by tube size, position, and number. For Ra = 10⁵ and 10³ without baffles, the Nusselt number increases by 74.59% and 9.57%, respectively, as ω* rises from 0 to 200. At ω* = 200, reducing the tube’s radial position from 0.45 - 0.3 increases the Nusselt number by 135.95% and 75.83% for Ra = 105 and 103, respectively, at a fixed r* = 0.03. Additionally, at Ra = 10⁵, ω* = 200, r* = 0.03, and e* = 0.35, reducing the number of tubes from 4 to 1 results in a 69.23% increase in the Nusselt number. Further analysis reveals that with flexible baffles, the Nusselt number is strongly influenced by tube size, radial position and number, especially at higher rotational speeds and Rayleigh numbers. Specifically, for Ra = 10⁵ and 10³, the Nusselt number increases by 82.9% and 10.2%, respectively, as ω* increases from rest to 200. At ω* = 200, Furthermore, for a smaller tube radius (r* = 0.01) with e* = 0.35, Nht = 4, and Ra = 10⁵, flexible baffles further improve skin friction reduction relative to the non-baffled configuration, achieving reductions of 83.6%, 83.3%, 43.7%, and 41.7% at ω* = 50, 100, 200, and 400, respectively. To promote the thesis, the study employs the Nelder-Mead optimization method to assess the impact of rotational speeds, tube radial positions, and Rayleigh numbers (Ra = 10³–10⁵) in identifying optimal performance conditions. The analysis finds peak performance at e* = 0.32378 and ω* = 366.48 for Ra = 10³, and at e* = 0.32 and ω* = 379.43 for Ra = 10⁵. These results underscore the importance of fine-tuning rotational speed and tube positioning as the Rayleigh number increases to maximize system efficiency. Several research papers derived from this thesis have been published in peer reviewed international journals indexed in Scopus and Clarivate databases.