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The heat transfer improvement using nanofluids inside varying shape heat exchangers is a still challenge to avoid from heat losses in chemical and petrochemical industries. In the stated study, the friction loss (f), pressure drop (∆P), average heat (have) transfer and average Nusselt (Nuave) numbers were evaluated numerically (ANSYS-FLUENT) and experimentally at varying 0.025 mass%, 0.05 mass%, 0.075 mass%, and 0.1 mass% concentrations of the low dimensional Zinc nanospheres-based nanofluids and base fluid (DW) in the square shaped heat exchanger. All the nanofluids and base fluid (DW) were assessed both experimentally and numerically for different thermophysical, hydrodynamic, and heat transfer characteristics. The addition of Zinc nanospheres in base fluid (DW) showed enhanced energy transportation at all mass% concentrations numerically and experimentally against Reynold numbers (Re) changing from 4550 to 20,367. Thermal conductivity, viscosity and density were measured at varying temperature ranges from 20 to 45 °C, where different changes were recorded in all properties against temperature values. Further, 2-D numerical model for single nanofluids was validated using laboratory scale distilled water (DW) as a base liquid. Further continuity, momentum, and energy equations were been evaluated by constructing a k−ɛ model and 2-dimensional domain. The maximum pressure drop (∆P/L) was recorded at 0.1 mass% which is 5152.72 m.Pas, while the friction loss (f) was 0.0188. Similarly, the average heat transfer (h) and Nusselt numbers (Nu) were calculated numerically and experimentally, where it has found the maximum heat transfer was 7095.25 Wm2 K−1 (61%) and the average Nusselt numbers (Nu) were 93.73 (57.3%) at the highest 0.1 mass%. Both numerical (ANSYS) and experimental results showed improved energy transportation at 0.1 mass% concentration against the highest Reynold number (Re) in comparison to base fluid (DW) and other mass%. The consequences confirmed the significance of the ANSYS model and experimental results with an average difference of ± 8.1%. [ABSTRACT FROM AUTHOR]

Covalent and non-covalent nanofluids were tested inside a circular tube fitted with twisted tape inserts with 45° and 90° helix angles. Reynolds number was 7000 ≤ Re ≤ 17,000, and thermophysical properties were assessed at 308 K. The physical model was solved numerically via a two-equation eddy-viscosity model (SST k-omega turbulence). GNPs-SDBS@DW and GNPs-COOH@DW nanofluids with concentrations (0.025 wt.%, 0.05 wt.% and 0.1 wt.%) were considered in this study. The twisted pipes' walls were heated under a constant temperature of 330 K. The current study considered six parameters: outlet temperature, heat transfer coefficient, average Nusselt number, friction factor, pressure loss, and performance evaluation criterion. In both cases (45° and 90° helix angles), GNPs-SDBS@DW nanofluids presented higher thermohydraulic performance than GNPs-COOH@DW and increased by increasing the mass fractions such as 1.17 for 0.025 wt.%, 1.19 for 0.05 wt.% and 1.26 for 0.1 wt.%. Meanwhile, in both cases (45° and 90° helix angles), the value of thermohydraulic performance using GNPs-COOH@DW was 1.02 for 0.025 wt.%, 1.05 for 0.05 wt.% and 1.02 for 0.1 wt.%. [ABSTRACT FROM AUTHOR]