<p>Enhancement in heat transfer can be realized by adding nanoparticles to boost the thermal properties of the base fluid, increase the tube surface area, and modify the flow trajectory of the fluid. In the present investigation, the convective heat transfer and pressure loss characteristics of Al₂O₃-Ethylene glycol and Al₂O₃-Water-based nanofluid in the vertically positioned helically coiled tube with micro-fin are studied by ANSYS FLUENT 19.2 through numerical methods. The effects of nanofluid mass fraction (1–4%), Reynolds number changing (10,000–30,000), micro-fin number (4–12), and the coil diameter (100–200 mm) on the heat transfer coefficient and pressure drop characteristics are carried out. The heat transfer and pressure drop characteristics are found to be highly sensitive to changes in Reynolds number and nanoparticle volume concentration. Furthermore, an increase in micro-fin density contributes to elevated heat transfer coefficients and higher pressure losses in nanofluid. The study confirms that the thermal performance index of Al₂O₃-Ethylene glycol nanofluid is universally lower than that of Al₂O₃-Water nanofluid across all nanofluid mass fraction.</p>