An updated review on the properties, fabrication and application of hybrid-nanofluids along with their environmental effects

Hybrid-nanofluids are potential fluids that present superior thermophysical properties and thermal performance than common heat transfer fluids mono-nanofluids. Hybrid nanofluid is a new fluid produced by dispersing two dissimilar types of nano-particles into the base fluid. Some researchers have reported that conventional coolants could be replaced by hybrid-nanofluids, particularly fluids that work at very high temperatures. Accordingly, these types of nanofluids could lead to saving energy as well as less harmful environmental impacts. Many researches have been performed on nanofluids in the past decade. Despite the uncertainties in the nanofluids thermal-conductivity, they are still considered as heat transfer fluids with a new technology. In recent years, researchers have been trying to utilize hybrid-nanofluids designed by mixing different nanofluids in mixtures or composite forms. The idea of hybrid-nanofluids to improve heat transfer performance and their advantages has led to relatively good expectations for their applications. This article evaluates recent researches on hybrid-nanofluids, including methods of fabrication, thermophysical properties, nano-particle types and their shapes, pressure drop and heat transfer characteristics, and their applications. Finally, the challenges, environmental and destructive effects of nano-particles on the human body and future approaches in the application of hybrid-nanofluids in heat transfer devices are discussed. (C) 2020 Elsevier Ltd. All rights reserved.