Renewable and Sustainable Energy Reviews 15 (2011) 1646–1668 Contents lists available at ScienceDirect Renewable and Sustainable Energy Reviews journal homepage: www.elsevier.com/locate/rser A review on applications and challenges of nanofluids R. Saidur a,∗ , K.Y. Leong b , H.A. Mohammad c a Department of Mechanical Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia b Department of Mechanical Engineering, National Defense University of Malaysia, Sg Besi Camp, 57000 Kuala Lumpur, Malaysia c Department of Mechanical Engineering, College of Engineering, Universiti Tenaga Nasional, Km 7, Jalan Kajang-Puchong, 43009 Kajang, Selangor, Malaysia article info Article history: Received 27 May 2010 Accepted 12 November 2010 Keywords: Applications of nanofluids Thermal conductivity Challenges of nanofluids abstract Nanofluids are potential heat transfer fluids with enhanced thermophysical properties and heat transfer performance can be applied in many devices for better performances (i.e. energy, heat transfer and other performances). In this paper, a comprehensive literature on the applications and challenges of nanoflu- ids have been compiled and reviewed. Latest up to date literatures on the applications and challenges in terms of PhD and Master thesis, journal articles, conference proceedings, reports and web materials have been reviewed and reported. Recent researches have indicated that substitution of conventional coolants by nanofluids appears promising. Specific application of nanofluids in engine cooling, solar water heating, cooling of electronics, cooling of transformer oil, improving diesel generator efficiency, cooling of heat exchanging devices, improving heat transfer efficiency of chillers, domestic refrigerator-freezers, cooling in machining, in nuclear reactor and defense and space have been reviewed and presented. Authors also critically analyzed some of the applications and identified research gaps for further research. Moreover, challenges and future directions of applications of nanofluids have been reviewed and presented in this paper. Based on results available in the literatures, it has been found nanofluids have a much higher and strongly temperature-dependent thermal conductivity at very low particle concentrations than conven- tional fluids. This can be considered as one of the key parameters for enhanced performances for many of the applications of nanofluids. Because of its superior thermal performances, latest up to date literatures on this property have been summarized and presented in this paper as well. However, few barriers and challenges that have been identified in this review must be addressed carefully before it can be fully implemented in the industrial applications. © 2011 Elsevier Ltd. All rights reserved. Contents 1. Introduction .......................................................................................................................................... 1647 2. Overview of applications of nanofluids .............................................................................................................. 1648 3. Thermal conductivity of nanofluids ................................................................................................................. 1649 4. Applications of nanofluids ........................................................................................................................... 1651 4.1. Cooling of electronics ......................................................................................................................... 1651 4.2. Nanofluids in cameras, microdevices, and displays .......................................................................................... 1653 4.3. Application in chillers ........................................................................................................................ 1653 4.4. Application in domestic refrigerator ......................................................................................................... 1654 4.5. Engine cooling/vehicle thermal management ............................................................................................... 1655 4.6. Detection of knock occurrence in a gas SI engine ............................................................................................ 1657 4.7. Application as a coolant in machining ....................................................................................................... 1657 4.8. Cooling of diesel electric generator [110] .................................................................................................... 1657 4.9. Diesel combustion ............................................................................................................................ 1658 4.10. Boiler flue gas temperature reduction ...................................................................................................... 1658 4.11. Solar water heating ......................................................................................................................... 1658 4.12. Cooling and heating in buildings ........................................................................................................... 1659 4.13. Application in transformer .................................................................................................................. 1659 ∗ Corresponding author. Tel.: +60 3 79674462; fax: +60 3 79675317. E-mail address: saidur912@yahoo.com (R. Saidur). 1364-0321/$ – see front matter © 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.rser.2010.11.035