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Article History

Received: 22 July 2023

Revised: 22 July 2023

Accepted: 15 January 2024

First Online: 9 September 2024

CONFLICT OF INTEREST

: The authors of this work declare that they have no conflicts of interest.

: <i>H</i> Pitch length of twisted tape (mm)<i>W</i> Width of twisted tape (mm)<i>P</i>/<i>d</i> Pitch ratio in corrugated tube<i>y</i> Twist ratio (H/W) Twisted tape thickness (mm)Pr Prandtl numberNu Nusselt number Specific heat capacity <i>f</i> Friction factor<i>K</i> Thermal conductivity of fluid <i>m</i> Consistency index (Pa s^<i>n</i>)<i>D</i> Diameter of tube (m)<i>L</i> Tube length (m) Inlet pressure (Pa) Average velocity (m/s) Outlet pressure (Pa)κ Turbulent kinetic energy ν Volume () Wall temperature <i>n</i> Power Law index Average heat transfer coefficient  Bulk temperature  External diameter (mm) Average heat transfer (W) Absorbed heat transfer (W) Input electrical power (W) Outlet temperature (°C) Inlet temperature (°C) Mass flow rate  Heat flux Re Reynolds number<i>R</i> Resistance (Ω) Voltage (V)(<i>e</i>/<i>D</i>) Height ratio in corrugated tube<i>V</i> Velocity vector (m/s)<b>Abbreviation</b>TT Typical twisted tapeexp ExperimentalPre Predicted<b>Greek symbols</b>ρ Density (kg/m³)μ Dynamic viscosity (N s/m²)Φ Volume concentration of nanofluid, %η Thermal performance factorβ Ratio of the nanolayer thickness to the original particle radiusε Dissipation rate of turbulent kinetic energy (m²/s³)ω Specific dissipation rate (s^–1)τ Shear stress (N/m²)<b>Subscripts</b>i Internalw Wallf Fluid0 Outeravg AverageMR Metznerapp Apparentbf Base fluidnf Nanofluidnp Nanoparticle