Currently, most heat exchanger systems use water, hydroalcoholic mixtures or oil. These three traditional options are low or very low heat transfer fluids with thermal conductivities of 0.61 0.25 and 0.145 W·m-1·K-1, for water, ethylene glycol and oil, respectively. Until now, these three liquids are the most frequently used solutions because they are cheap, easily accessible and in the case of low demanding tasks, they are effective. Nevertheless, for some applications the equipment size or weight, and/or the process time are too high, and it is therefore necessary to seek alternatives.
The use of different grades of graphene to prepare aqueous colloidal suspensions offer the best option from a performance point of view and effectiveness one. Currently, the cost of graphene is not too high, and at low dosage, around 2%, the selling price of the nanofluid could be competitive. On the other hand, graphene colloidal solutions are lubricants and stable in a wide range of pH, therefore the corrosion and erosion problems of metal oxide based nanofluids should not appear. And finally, the use of graphene nanofluids is an improvement from CFC’s regarding care for the environment.