Cheedarala Ravi Kumar, Song Jung Il
Department of Mechanical Engineering, Changwon National University Changwon 51140 Republic of Korea
RSC Adv. 2019 Oct 7;9(54):31735-31746. doi: 10.1039/c9ra04563e. eCollection 2019 Oct 1.
We report the synthesis of thermally heated pop-up reduced graphene oxide (Pop-rGO) and its nanofluid (Pop-rGO-Nf) in DI water for extended critical heat flux (CHF) in a nucleate pool boiling experiment. When Pop-rGO-Nf is boiled over a nichrome (NiCr) wire heater the CHF values were increased up to 132%, 156%, and 175% with increasing concentrations of 0.0005 vol%, 0.001 vol%, and 0.005 vol% at heat fluxes of '' = 264 333 kW m, 339 202 kW m, and 327 895 kW m, respectively, because of the higher surface area of 430 m g. We also found a decrease in the CHF value from 0.05 vol% (175%) to 0.01 vol% (153%) for Pop-rGO-Nf due to the nanofluid concentration reaching the saturation point. After nucleate pool boiling, the developed Pop-rGO-Nf built-up layer on the NiCr wire surface showed regular π-π stacking with novel micro-rippled structures having uniform nanocavities and nanochannels. The nanocavities strongly helped vapor bubbles to escape from the NiCr wire surface. In addition, the nanochannels were formed by hydrogen bonding of adjacent carboxyl groups of each Pop-rGO nanosheet. The surface hydrophobicity of the built-up layers increased with the increase of the concentration of the Pop-rGO-Nfs, and the surface morphology, roughness average ( ) and hydrophobicity were determined using FE-SEM, AFM and contact angle (CA) analysis. In our present investigation, during and after the nucleate CHF experiments with Pop-rGO-Nfs, for the first time, we obtained a higher CHF value of 175% at 0.01 vol% and a higher CA of 118° obtained at 0.05 vol%, due to the increase in surface hydrophobicity and the novel micro-rippled structures. We anticipate that the present results suggest that pool boiling employing Pop-rGO-Nf can dissipate the critical heat flux of electronic chips to a greater extent, allowing the enhancement of the cooling performance in existing two-phase heat transfer devices.
我们报告了在去离子水中热加热弹出式还原氧化石墨烯（Pop-rGO）及其纳米流体（Pop-rGO-Nf）的合成，用于在池沸腾实验中扩展临界热流密度（CHF）。当Pop-rGO-Nf在镍铬（NiCr）丝加热器上沸腾时，在热流密度分别为264333kW/m²、339202kW/m²和327895kW/m²的情况下，随着浓度从0.0005体积%、0.001体积%增加到0.005体积%，CHF值分别提高了132%、156%和175%，这是因为其具有430m²/g的较高比表面积。我们还发现，由于纳米流体浓度达到饱和点，Pop-rGO-Nf的CHF值从0.05体积%（175%）降至0.01体积%（153%）。在池沸腾后，在NiCr丝表面形成的Pop-rGO-Nf堆积层呈现出规则的π-π堆积，具有新颖的微波纹结构，带有均匀的纳米腔和纳米通道。纳米腔极大地帮助蒸汽泡从NiCr丝表面逸出。此外，纳米通道是由每个Pop-rGO纳米片相邻羧基的氢键形成的。堆积层的表面疏水性随着Pop-rGO-Nf浓度的增加而增加，并使用场发射扫描电子显微镜（FE-SEM）、原子力显微镜（AFM）和接触角（CA）分析来确定表面形态、平均粗糙度（ ）和疏水性。在我们目前的研究中，在使用Pop-rGO-Nf进行池沸腾CHF实验期间和之后，由于表面疏水性增加和新颖的微波纹结构，我们首次在0.01体积%时获得了175%的较高CHF值，在0.05体积%时获得了118°的较高接触角。我们预计，目前的结果表明，采用Pop-rGO-Nf的池沸腾可以在更大程度上消散电子芯片的临界热流，从而提高现有两相传热设备的冷却性能。
