The impact of using twisted double tube of innovative turbulator on the efficiency of a flat panel solar collector with geometric optimization

Background: Fluids as water, ethylene glycol, etc. employed to enhance heat transfer, have a lower thermal conductivity (TC) coefficient compared to metals and even metal oxides. This paper presents computational fluid dynamics (CFD) simulation of the twisted double tube heat exchanger (HE) filled with two-phase MWCNT-TiO2/ water hybrid nanofluid (Hnf). Methods: The FLUENT 16 software is employed for numerical simulations of the HE with novel turbulator. The hybrid nanofluid is simulated using the two-phase mixture model and turbulent flow is modeled utilizing Realizable k-? turbulence model. The Reynolds number (Re) alters from 7000 to 28000, the volume fraction of nanoparticles (?) varies from 1.0 to 4.0%, and the pitch ratio of the innovative turbulator is 1.0, 2.0, 3.0, and 4.0. Outcomes proved average Nusselt number (Nuave) and pressure drop are strongly influenced by Re and ?. Results: The maximum thermal efficiency and HE pressure drop correspond to ? = 4%, Re = 28000, and a pitch ratio of 4. When ? = 4% and Re = 28000, adding turbulator with a pitch ratio of 4 inside the heat exchanger enhances Nuave by 106.92% in comparison with heat exchanger without turbulators. When ? = 4% and Re = 28000, adding turbulator with a pitch ratio of 4 inside the heat exchanger increases the pressure drop by 296.19% compared to HE without turbulators. Finally, exergy efficiency of HE with a turbulator with a pitch ratio of 4 is improved by 21.83% as Re increases from 7000 to 28000 when ? = 4%.