New nanoparticle enhanced fluids

The concept of adding small solid particles to a base fluid to increase the thermal properties of suspension has been long since practiced using millimetre- or micrometre-sized particles, which has led to problems, such as poor suspension stability and channel clogging, which limited practical applicability. In 1995, Choi proposed nanofluids (NF) to increase the thermal conductivity of heat transfer fluids(HTF). NFs are defined as dilute suspensions with solid particles smaller than 100 nm. NFs present some major advantages over conventional colloidal suspensions, such as high stability, reduced particle clogging and high heat transfer capabilities. All these potential advantages have boosted research in the NFs field (more than 10 000 papers have been published in research journals in the last years). Despite the huge effort made in the research and development of NFs in the last decade, there are still significant barriers to their market uptake by commercial implementation in industrial applications. NFs are advanced materials developed by nanotechnology and fall, therefore, within one of the Key Enabling Technologies (KET) supported by the European Commission. In addition, they are mentioned in the Strategic Energy Technology Plan (SET Plan) and the Solar Thermal Electricity Technology Roadmap as potential elements to improve the efficiency of heat exchange, to thus contribute to meet the European Council energy objectives for 2025. NFs constitute an interdisciplinary research topic by nature and in the last years, other nanoparticles enhanced fluids were engineered (i.e. hybrid nanofluids, PEG based nanofluids and ionanofluids).