Fewer Dimensions for Higher Thermal Performance: A Review on 2D Nanofluids

The current work aims to offer a specific overview of the homogeneous dispersions of 2D nanomaterials in heat transfer base fluids—so-called 2D nanofluids. This data compilation emerged from the critical overview of the findings of the published scientific articles regarding 2D nanofluids. The applicability of such fluids as promising alternatives to the conventional heat transfer and thermal energy storage fluids is comprehensively investigated. These are fluids that simultaneously possess superior thermophysical properties and can be processed according to innovative environmentally friendly methods and techniques. Furthermore, their very reduced dimensions are suitable for the decrease in the size of thermal management systems, and the devices have attracted a lot of attention from researchers in different fields. Some examples of 2D nanofluids are those which incorporate graphene, graphene oxide, hexagonal boron nitride, molybdenum disulfide nanoparticles, and hybrid formulations. Although the published results are not always consistent, it was found that this type of nanofluid can improve the thermal conductivity of traditional base fluids by more than 150%, achieving values of approximately 6500 W·m−1·K−1 and interface thermal conductance above 50 MW·m−2·K−1. Such beneficial features permit the attainment of increments above 60% in the overall efficiency of photovoltaic/thermal solar systems, a 70% reduction in the entropy generation in parabolic trough collectors and increases of approximately 200% in the convective heat transfer coefficient in heat exchangers and heat pipes. These findings identify those fluids as suitable heat transfer and thermal storage media. The current work intends to partially suppress the literature gap by gathering detailed information on 2D nanofluids in a single study. The thermophysical properties of 2D nanofluids and not of their traditional counterparts, as it is usually encountered in the literature, and the extended detailed sections dedicated to the potential applications of 2D nanofluids are features that may set this research apart from previously published works. Additionally, a major part of the included literature references consider exclusively 2D nanomaterials and the corresponding nanofluids, which also constitutes a major gathering of specific data regarding these types of materials. Upon its conclusion, this work will provide a general overview of 2D nanofluids.