Alam Md Shah, Nahar Bodrun, Gafur Md Abdul, Seong Gimyeong, Hossain Muhammad Zamir
Department of Chemistry, Jagannath University, Dhaka 1100, Bangladesh.
Pilot Plant & Process Development Centre, Bangladesh Council of Scientific and Industrial Research (BCSIR), Dhaka 1205, Bangladesh.
Nanomaterials (Basel). 2022 May 5;12(9):1568. doi: 10.3390/nano12091568.
This paper presents the experimental forced convective heat transfer coefficient (HTC) of nanorods (NRs) zinc oxide-ethylene glycol nanofluids (ZnO-EG NFs) in laminar flow. First, ZnO NRs were synthesized using a hydrothermal method that uses zinc acetate dihydrate [Zn(CHCOO)·2HO] as a precursor, sodium hydroxide as a reducing agent, and polyvinylpyrrolidone (PVP) as a surfactant. The hydrothermal reaction was performed at 170 °C for 6 h in a Teflon-lined stainless-steel tube autoclave. The sample's X-ray diffraction (XRD) pattern confirmed the formation of the hexagonal wurtzite phase of ZnO, and transmission electron microscopy (TEM) analysis revealed the NRs of the products with an average aspect ratio (length/diameter) of 2.25. Then, 0.1, 0.2, and 0.3 vol% of ZnO-EG NFs were prepared by adding the required ZnO NRs to 100 mL of EG. After that, time-lapse sedimentation observation, zeta potential (ζ), and ultraviolet-visible (UV-vis) spectroscopy was used to assess the stability of the NFs. Furthermore, the viscosity () and density () of NFs were measured experimentally as a function of vol% from ambient temperature to 60 °C. Finally, the HTC of NFs was evaluated utilizing a vertical shell and tube heat transfer apparatus and a computer-based data recorder to quantify the forced convective HTC of NFs in laminar flow at Reynolds numbers () of 400, 500, and 600. The obtained results indicate that adding only small amounts of ZnO NRs to EG can significantly increase the HTC, encouraging industrial and other heat management applications.
本文介绍了纳米棒（NRs）氧化锌-乙二醇纳米流体（ZnO-EG NFs）在层流中的实验强制对流换热系数（HTC）。首先，采用水热法合成ZnO NRs，该方法使用二水合醋酸锌[Zn(CH₃COO)₂·2H₂O]作为前驱体，氢氧化钠作为还原剂，聚乙烯吡咯烷酮（PVP）作为表面活性剂。水热反应在聚四氟乙烯内衬的不锈钢管高压釜中于170℃下进行6小时。样品的X射线衍射（XRD）图谱证实了ZnO六方纤锌矿相的形成，透射电子显微镜（TEM）分析表明产物的NRs平均长径比（长度/直径）为2.25。然后，通过向100 mL乙二醇中加入所需的ZnO NRs制备了体积分数为0.1%、0.2%和0.3%的ZnO-EG NFs。之后，利用延时沉降观察、zeta电位（ζ）和紫外可见（UV-vis）光谱来评估NFs的稳定性。此外，还在从环境温度到60℃的范围内，实验测量了NFs的粘度（μ）和密度（ρ）随体积分数的变化。最后，利用立式壳管式传热装置和基于计算机的数据记录仪评估NFs的HTC，以量化NFs在雷诺数（Re）为400、500和600时层流中的强制对流HTC。所得结果表明，仅向乙二醇中添加少量的ZnO NRs就能显著提高HTC，这对工业和其他热管理应用具有促进作用。
