Abstract This paper addressed the scarcity of experimental studies on the duo effect of magnetic excitation and hybrid nanofluid on the thermo-convection characteristics in enclosures. Novel Fe2O3-MWCNT (80:20)/deionized water (DIW) nanofluids with volume concentrations (φ) of 0.05–0.4 vol% were employed in a rectangular cavity exposed to magnetic excitation (4.89–21.95 mT) to examine the thermo-convection heat transfer behavior. The prepared hybrid magnetic nanofluids (HMNFs) were characterized for their stability, viscosity, thermal conductivity, and morphology. The DIW and stable HMNFs were charged into the cavity and differentially heated at ΔT of 20–35 °C under steady conditions. The results showed that without magnetic excitation, the average Nusselt number (Nuav) were observed to augment as Rayleigh number (Ra) and ΔT increased. Nuav and average heat transfer ( Q av) were augmented for φ ≤ 0.2 vol% but they depreciated with φ > 0.2 vol% when compared with DIW. As the viscosity of HMNFs and φ increased heat transfer was noticed to depreciate. At ΔT = 35 °C, highest Nuav (11.33%) and Q av (11.21%) were achieved with φ = 0.05 vol%. With the magnetic excitation of 4.89–21.95 mT applied to the bottom, side (vertically and horizontally) and top (perpendicular and parallel to ΔT direction) walls of the cavity containing 0.05 vol% HMNF at ΔT = 35 °C, Q av was enhanced by 0.86%–1.46% and 1.72%–5.02% for the bottom and side walls when compared with the case of no magnetic excitation. Highest Q av (2.69%–5.02%) was recorded when the magnetic excitation was applied vertically on the side wall. Conclusively, the obtained results were observed to be strongly related to φ, ΔT, strength of magnetic excitation, use of HMNFs, position, and configuration of magnetic excitation.

中文翻译：

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水基磁性杂化纳米流体在磁激发矩形腔内传热性能的实验研究

摘要 本文解决了关于磁激发和混合纳米流体对外壳热对流特性的双重影响的实验研究的稀缺性。体积浓度 (φ) 为 0.05–0.4 vol% 的新型 Fe2O3-MWCNT (80:20)/去离子水 (DIW) 纳米流体被用于暴露于磁激发 (4.89–21.95 mT) 的矩形腔中，以检查热对流传热行为。制备的混合磁性纳米流体 (HMNFs) 具有稳定性、粘度、导热性和形态特征。将 DIW 和稳定的 HMNF 装入腔体并在稳定条件下以 20-35°C 的 ΔT 差异加热。结果表明，在没有磁激励的情况下，观察到平均努塞尔数 (Nuav) 随着瑞利数 (Ra) 和 ΔT 的增加而增加。当 φ ≤ 0.2 vol% 时，Nuav 和平均传热 (Q av) 增加，但与 DIW 相比，当 φ > 0.2 vol% 时，它们会贬值。随着 HMNF 的粘度和 φ 增加，传热被注意到贬值。在 ΔT = 35 °C 时，最高的 Nuav (11.33%) 和 Q av (11.21%) 达到了 φ = 0.05 vol%。将 4.89–21.95 mT 的磁激发施加到含有 0.05 vol% HMNF 的腔体的底部、侧面（垂直和水平）和顶部（垂直和平行于 ΔT 方向）壁，在 ΔT = 35 °C 时，Q av 增强与无磁激励的情况相比，底部和侧壁分别增加了 0.86%–1.46% 和 1.72%–5.02%。当磁激励垂直施加在侧壁上时，记录到最高 Q av (2.69%–5.02%)。最后，观察到所得结果与 φ、ΔT、