Thermal Conductivity of Ionic Liquid-Based Nanofluids Containing Magnesium Oxide and Aluminum Oxide Nanoparticles

Abstract

A promising nanomaterial, magnesium oxide (MgO) and a commonly studied nanomaterial, aluminum oxide (Al₂O₃) were used to enhance the thermal conductivity of two ionic liquids, i.e., 1-ethyl-3-methylimidazolium dicyanamide ([emim][DCa]) and 1-ethyl-3-methylimidazolium tricyanomethanide ([emim][TCM]) of potential as heat transfer medium. Effects of nanoparticle material, size, shape as well as mass concentration on thermal conductivity enhancement were investigated experimentally, along with stability analysis of the nanoparticle suspensions. The thermal conductivity of [emim][TCM] can be enhanced by up to 40% by adding 15 wt.% of polyhedral MgO nanoparticles. The thermal conductivity of Al₂O₃ ionanofluids does not vary much with nanoparticle size while that of MgO ionanofluids tends to increase as the nanoparticle size decreases. The Maxwell-Garnett model and the Hamilton–Crosser model could estimate the thermal conductivity of [emim][DCa]-based nanofluids containing Al₂O₃ and MgO nanoparticles, respectively, while under-prediction prevailed for [emim][TCM]-based nanofluids. Besides, challenges were encountered during zeta potential measurements created by the ionic liquids themselves. New methods need to be developed to correctly measure the zeta potential of ionic liquid-based nanofluids.

Acknowledgments

The Swedish Research Council is gratefully acknowledged for financial support of this research. This work is a contribution to the EU COST Action CA15119: NanoUptake. The company Malvern Panalytical is acknowledged for support with zeta potential measurements. The authors would like to thank Professor Lars Wadsö at LTH for help with instrument TPS 2500. The authors are affiliated members of NanoLund.

Disclosure Statement

No potential conflict of interest was reported by the authors.

Additional information

Notes on contributors

Marcus Hothar

Marcus Hothar is a PhD student at the Department of Energy Sciences at the Faculty of Engineering of Lund University, Sweden. He obtained his master’s degree in chemical engineering at Lund University in 2018 and has since then been pursuing his doctoral degree. His fields of interest are heat transfer, colloidal chemistry, nanotechnology, and sustainability. The research topic he pursues is nanofluids, especially those based on ionic liquids, and their potential as heat transfer fluids.

Zan Wu

Zan Wu is currently an Associate Professor at the Department of Energy Sciences, Lund University, Sweden. He received his BS and PhD from Zhejiang University, Hangzhou, China in 2008 and 2013, respectively. He worked as a postdoctoral fellow, a senior researcher, and then he was promoted as tenured Associate Professor in 2018, all at Lund University. He is leading projects granted by various funding agencies, especially the Swedish Research Council. His research interests are mainly multiphase flow, heat transfer enhancement by micro/nanostructures, phase change, microreactors, microfluidics and nanofluidics, and renewable energy. He has coauthored about 100 peer-reviewed journal articles, 30+ peer-reviewed conference papers, 1 invited monograph, and 6 invited book chapters. The h-index is 27, and the number of citations is more than 2,900. He currently serves as associate editor of the Heat Transfer Engineering journal.

Bengt Sundén

Bengt Sundén received his MSc in 1973 and PhD in 1979 and became Docent in 1980, all from Chalmers University of Technology, Gothenburg, Sweden. He was appointed Professor of Heat Transfer at Lund University, Lund, Sweden in 1992 and served as Head of the Department of Energy Sciences, Lund University for 21 years, 1995–2016. He has served as Professor Emeritus and Senior Professor since 2016. The research activities mainly include various heat transfer enhancement techniques, gas turbine heat transfer, computational modeling, and analysis of multiphysics and multiscale transport phenomena for fuel cells, nano- and microscale heat transfer, boiling and condensation, aerospace heat transfer, and thermal management of batteries. He has supervised 51 PhD students and many post docs as well hosted many visiting scholars and PhD students. He serves as Guest or Honorary Professor of several prestigious universities. He is a Fellow of ASME, a regional editor for Journal of Enhanced Heat Transfer since 2007, an associate editor of Heat Transfer Research since 2011, ASME J. Heat Transfer, 2005–2008, ASME J. Thermal Science, Engineering and Applications, 2010–2016, and ASME J. Electrochemical Energy Conversion and Storage, 2017–2023. He was a recipient of the ASME Heat Transfer Memorial Award 2011 and Donald Q. Kern Award 2016. He received the ASME HTD 75th Anniversary Medal 2013. He has edited 30+ books and authored 3 major textbooks. He has published more than 500 papers in well-established and highly ranked journals. The h-index is 47, and the number of citations is more than 10,000.