Chemical Engineering Program, Texas A&M University, College Station, TX 77843-3122, USA.
Center for Advanced Materials Research, University of Sharjah, 27272 Sharjah, United Arab Emirates; Department of Sustainable and Renewable Energy Engineering, University of Sharjah, 27272 Sharjah, United Arab Emirates.
Sci Total Environ. 2021 Apr 1;763:144202. doi: 10.1016/j.scitotenv.2020.144202. Epub 2020 Dec 25.
Nanofluids (NFs) have been expanding their applications in many areas as high-performance heat transfer fluid (HTF) for heating and cooling purposes. This is mainly due to the improved thermophysical properties relative to the base fluid (BF). The addition of nanoparticles (NPs) to BF, to obtain NFs, increases the thermal conductivity, hence better heat transfer properties and thermal performance. The properties of NFs can be considered somehow intermediate between those of the BF and the added solid NPs. The improved heat transfer using NFs results in increased energy conversion efficiency, which results in reduced energy consumption for heating or cooling applications. BF and their environmental impacts (EIs) have been widely discussed within the scope of their applications as a HTF, with most of the attention given to the improved energy efficiency. The IEs of NPs and their toxicity and other characteristics have been extensively studied due to the widespread applications on newly engineered NPs. However, with the evolution of expanding the applications of NFs, the different EIs were not well addressed. The discussion should consider both the base fluid and NPs added in combination as the NF constitutes. The current work presents a brief discussion on the EIs of NFs. The discussion presented in this work considers the NPs as the primary contributor to the EIs of different NFs. It was found that the EIs of NFs depend significantly on the type of NP used, followed by the BF, and finally, the loading of NPs in BF. The use of non-toxic and naturally occurring NPs at lower NPs loading in water as NF promises a much lower EIs in terms of toxicity energy requirements for production, and other EIs, while still maintaining high thermal performance. The production methods of both NPs, i.e., synthesis route, and NF, i.e., one-step or two-step, were found to have a significant effect on the associated EIs of the produced NF. The simpler NP synthesis route and NF production will result in much lower chemicals and energy requirements, which in turn reduce the EIs.
纳米流体（NFs）作为一种高性能传热流体（HTF），在加热和冷却方面的应用不断扩大。这主要是由于其相对于基础流体（BF）的热物理性能得到了改善。向 BF 中添加纳米颗粒（NPs）以获得 NFs，可以提高导热系数，从而改善传热性能和热性能。NFs 的性能可以被认为介于 BF 和添加的固体 NPs 之间。使用 NFs 可以提高传热效率，从而提高能源转换效率，降低加热或冷却应用的能耗。BF 及其环境影响（EIs）在作为 HTF 的应用范围内已经得到了广泛的讨论，其中大部分注意力都集中在提高能源效率上。由于对新设计的 NPs 的广泛应用，NPs 的毒性和其他特性及其环境影响（EIs）已经得到了广泛的研究。然而，随着 NFs 应用范围的不断扩大，不同的 EIs 并没有得到很好的解决。讨论应该考虑到 NF 由基础流体和添加的 NPs 共同构成的情况。目前的工作对 NFs 的 EIs 进行了简要讨论。本工作认为 NPs 是不同 NFs 环境影响的主要贡献者。结果表明，NFs 的 EIs 显著取决于所使用的 NP 类型，其次是 BF，最后是 BF 中 NPs 的负载量。在水中使用无毒且天然存在的 NPs 作为 NF，在生产毒性、能源需求和其他 EIs 方面具有较低的要求，同时仍保持较高的热性能。发现 NPs 和 NF 的生产方法，即合成路线和一步法或两步法，对所产生的 NF 的相关 EIs 有显著影响。更简单的 NP 合成路线和 NF 生产将导致化学品和能源需求大大降低，从而降低 EIs。
