**6. Thermal Applications**

The previous sections showed how dispersing carbon-based nanomaterials in conventional working fluids could positively affect these liquids properties, especially when it comes to their overall thermal conductivity. On the contrary, this section concentrates on utilizing carbon-based suspensions in three heat and mass transfer systems widely used in the energy sector, namely, PTSCs, nuclear reactors systems, and AC&R systems. This is because the previous attempts that many researchers undertook to enhance the performance of these systems were mainly through design modifications, such as adding turbulators, geometric and construction materials variations, and surface alterations. However, these techniques have reached a point where limited enhancements can be accomplished. Therefore, to break these boundaries for further progress, some scientists have proposed exchanging the working fluids of these thermal applications with nanofluids [293]. This is because employing a working fluid that possesses higher thermal conductivity would eventually improve the heat transfer rate in these systems, as will be demonstrated next.
