Heat transfer performance and hydrodynamic behavior of turbulent nanofluid radial flows Gilles Roy a, * , Iulian Gherasim b , François Nadeau a , Gérard Poitras a , Cong Tam Nguyen a a Faculty of Engineering, Université de Moncton, Moncton, NB, E1A 3E9, Canada b Department of Building Services, Faculty of Civil Engineering and Building Services, Technical University “Gheorghe Asachi”, 45A Mangeron, 700050 Iasi, Romania article info Article history: Received 25 October 2011 Received in revised form 14 March 2012 Accepted 14 March 2012 Available online 22 April 2012 Keywords: Turbulent radial flow Nanofluids Confined radial flow Heat transfer enhancement Pumping power Nanofluid performance Performance evaluation criterion CFD Numerical investigation abstract This paper presents a numerical investigation of heat transfer and hydrodynamic behavior of various types of water-based nanofluids inside a typical radial flow cooling device. Turbulent radial nanofluid flow between two parallel disks with axial injection is considered. Several turbulence models were evaluated. The RANS-based k  u SST turbulence model was chosen for subsequent simulations. A single phase fluid approach was used throughout with temperature dependant nanofluid effective properties. Results show that although heat transfer enhancement is found for all types of nanofluids considered, energy-based performance comparisons indicate that they do not necessarily represent the most effi- cient coolants for this type of application and flow conditions. Ó 2012 Elsevier Masson SAS. All rights reserved. 1. Introduction Nanoparticle suspensions (i.e. nanofluids) have generated an impressive amount of interest over the past 15 years. Indeed, the lackluster performances of typical coolants such as water, ethylene glycol and various oils have lead engineers to seek solutions for the increasing needs of heat transfer enhancement in current and future applications. For example, the reduction in size of high- performance electronic equipment (including micro processors) typically result in higher heat densities requiring more effective means of cooling. This can be accomplished by incorporating physical changes to the system (i.e. modifying the geometry of cooling apparatus) or by using alternate coolants. A review of literature on nanofluids will illustrate that the bulk of research on the subject initially consisted of determining nanofluid effective thermophysical properties such as thermal conductivity and viscosity (see for example Refs. [1,2] and [3]). More recently, attention has turned to their potential as coolants in practical engineering applications. Indeed, several studies on confined flow applications, including microchannels [4], radiator flat tubes [5] and finned tube heating units [6], have illustrated that nanofluids do have interesting heat transfer enhancement capabilities that would render them good candidates for usage in practical or industrial applications. Although several authors acknowledge that increases in viscosity will undoubtedly have effects on the overall performance of nanofluids in confined flow applications (for example, [7]), few have evaluated their overall performance. In some applications, their use could be somewhat compromised because of such increases in viscosity. Indeed, some authors have come to the conclusion that nanofluids are typically not favorable solutions when an overall energy balance analysis is considered, [8,9]. Furthermore, some studies have shown experimentally that the heat transfer of a SiC particle suspension in water is less effi- cient than using the base fluid alone, [10]. On the other hand, they found that the same SiC nanoparticles placed in an ethylene glycol/ water mixture (50/50 volume ratio) will improve the cooling efficiency. One other potentially interesting application of nanofluids recently considered is the confined impinging jet and/or radial flow cooling device. These types of flows are of considerable interest in the engineering community because of their numerous * Corresponding author. E-mail address: gilles.c.roy@umoncton.ca (G. Roy). Contents lists available at SciVerse ScienceDirect International Journal of Thermal Sciences journal homepage: www.elsevier.com/locate/ijts 1290-0729/$ e see front matter Ó 2012 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.ijthermalsci.2012.03.009 International Journal of Thermal Sciences 58 (2012) 120e129