Particle concentration levels of various nanofluids in plate heat exchanger for best performance Arun Kumar Tiwari a , Pradyumna Ghosh b , Jahar Sarkar b,⇑ a Department of Mechanical Engineering, Institute of Engineering &Technology, GLA University, Mathura 281406, India b Department of Mechanical Engineering, Indian Institute of Technology (BHU), Varanasi 221005, India article info Article history: Received 3 December 2014 Received in revised form 29 April 2015 Accepted 29 May 2015 Keywords: Nanofluids Particle volume fraction Experimentation Heat transfer Pressure drop Best performance abstract A heat exchange device using nanofluid needs to operate at best nanoparticle loading to get the maxi- mum heat transfer performance. In this paper, an attempt has been made to optimize different nanofluid particle volume fractions based on a maximum heat transfer rate, convective heat transfer coefficient, overall heat transfer coefficient, effectiveness and performance index. The novelty of the present study is the optimization of particle volume fraction of various nanofluids based on experimentation in the commercial plate heat exchanger for wide range of nanoparticle volume fraction (0–3%). Effects of other operating conditions on the optimization have been discussed as well. Results show that for maximum enhancement of heat transfer characteristics, different nanofluids work at different optimum volume concentrations. For CeO 2 /water, Al 2 O 3 /water, TiO 2 /water and SiO 2 /water nanofluids, the optimum volume concentrations are 0.75%, 1%, 0.75% and 1.25%, respectively, at the flow rate of 3 lpm. The corresponding maximum heat transfer enhancements are about 35.9%, 26.3%, 24.1%, and 13.9%, respectively. Present study indicates that the optimum concentration for maximum performance index is lower than that for maximum heat transfer rate. Moreover the effect of nanomaterials is more predominant than that of heat transfer fluid temperature or volume flow rate. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction To crater the growing demand of energy density, nanofluids (innovative heat transfer fluids-suspended by nanometer-sized solid particles) have been proposed for performance improvement of various heat exchange devices and large number of research works has been published within last two decades. Due to a num- ber of advantages, over the years the use of plate heat exchangers has rapidly gone up in various engineering applications. As a result, there is a growing academic interest in heat transfer characteristics of plate heat exchanger by using nanofluids. Even as work with nanofluids has started for about the last two decades, research on plate heat exchanger using nanofluids is a recent development. A large number of studies have been reported on both numerical and experimental investigations of plate heat exchangers by using various nanoparticles (Al 2 O 3 , ZnO, CuO, TiO 2 , SiO 2 and carbon nanotube)-dispersed water, or, by using ethylene glycol-based nanofluids. Reported studies include comparison of various nanofluids for plate heat exchanger and the effects of var- ious operating and design parameters (temperature, flow rate, chevron angle, nanoparticle loading, etc.) with various configura- tions on the heat transfer, pressure drop and energetic as well as exergetic performances. A large number of numerical and experi- mental [1–21] investigations have been carried out to study both laminar and turbulent regimes. Recently, Safi et al. [22] calculated heat transfer coefficient of multiwalled carbon nanotube–TiO 2 hybrid nanofluid in plate heat exchanger through experiments. It has been observed [23] that there is an optimum nanoparticle loading (or concentration) yielding maximum performance of heat exchangers. Although, a large number of studies have showed the effect of particle loading of nanofluids on the heat exchange perfor- mances, literature on the optimization of particle loading are very limited. Xie et al. [23] first experimentally optimized the diamond nanoparticle loading by varying in the range of 0.5–2% for maxi- mum heat transfer coefficient through an in-tube convective heat transfer. Corcione and his co-workers [24–31] numerically opti- mized particle loading for natural convection heat transfer of nanofluids in plate and enclosures with various configurations and annular spaces between concentric cylinders. Jamshidi et al. [32] statistically optimized particle volume fraction, based on numerical data for helical tube. Corcione and his colleagues [33– 35] also numerically optimized particle loading of nanofluids through an in-tube heat transfer for both laminar and turbulent http://dx.doi.org/10.1016/j.ijheatmasstransfer.2015.05.118 0017-9310/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +91 9919787557. E-mail address: jsarkar.mec@itbhu.ac.in (J. Sarkar). International Journal of Heat and Mass Transfer 89 (2015) 1110–1118 Contents lists available at ScienceDirect International Journal of Heat and Mass Transfer journal homepage: www.elsevier.com/locate/ijhmt