An overview of sustainability of heat exchangers and solar thermal applications with nanofluids: A review

Nanofluids have been studied as an innovative alternative fluid solution to enhance the efficiency and profitability of thermal systems in industrial, commercial, and residential applications. The increment of efficiency in thermal systems has many advantages, for example, the reduction of environmental impact, lower energy consumption, and lower costs. In recent years, nanofluids have been economically and environmentally evaluated based on sustainability methodologies to determine their benefit in thermal systems. Hence, the purpose of this work is to highlight the progress of nanofluids in thermal applications and to present an overview of their benefits and areas of opportunity, to ensure a sustainable technological development. Therefore, this work provides a perspective on sustainability assessments of simple and hybrid nanofluids used in thermal systems, such as heat exchangers, solar collectors, and hybrid photovoltaic-thermal (PVT) solar systems focusing on life cycle methodology. Even though nanofluids have to overcome different challenges before becoming a feasible technology, it is indisputable that stable nanofluids with the right nanoparticle selection at an optimum volume concentration, can be implemented in a thermal system bringing positive economic and environmental results.