Discussion of Polyethylene Glycol Mixtures and PEG + MWCNT Nanocolloids’ Behavior in Thermal Applications

Nanocolloids are nanoparticles suspended in fluids with the aim of improving fluid capability at heat transfer, with a focus on thermal conductivity. The major advantage is the increase in thermal conductivity, with a certain influence on isobaric heat capacity and viscosity. Nevertheless, PEGs are able to create steady suspensions due to their chemical composition and are used in a number of applications. This paper discusses both the advantages and the drawbacks of a suspension of PEG 400 and MWCNT nanoparticles in terms of its relevance for heat transfer applications. Our investigation is built on a complex experimental procedure, as well as an analysis of the state of the art and a discussion of the experimental results in the context of the Prandtl number and thermal diffusivity. This analysis also includes different performance evaluation criteria that are extensively employed both in the heat transfer literature and in practice. The addition of MWCNTs to polyethylene glycol decreases the thermal transport, being influenced by both temperature and the addition of NPs. The results for MWCNT nanocolloids indicate an intensification of the pumping power of up to 29.7%. Also, an interesting option is the use of PEG mixtures as base fluids in order to combine their properties.