Enhancement of thermal conductivity of Cu-Cr dispersed nanofluids according to multiscale modeling Sarbeswar Das a , V. Karthik a , Shyamal Kumar Pabi a , Asit Behera b , Swadhin Kumar Patel c , Biswajit Swain c , Rakesh Roshan c , A. Behera c a Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Kharagpur 721302, India b School of Mechanical Engineering, Kalinga Institute of Industrial Technology, Bhubaneswar 751024, India c Department of Metallurgical and Materials Engineering, National Institute of Technology, Rourkela 769008, India article info Article history: Received 15 January 2020 Accepted 8 March 2020 Available online xxxx Keywords: Nanofluids Mechanical alloying Brownian motion MD-Stochastic model Thermal conductivity abstract Nanofluids are the suspension of nanoparticles (<100 nm) in conventional heat transfer fluids like water, ethylene glycol, etc. They often show enhanced thermal conductivity as compared to the base fluids. In the present work, thermal conductivity enhancement of Cu-Cr dispersed nanofluids is being studied by experiments as well as modeling. The modeling of the nanofluid is based on the mechanism that evenly dispersed nanoparticles within a nanofluid undergo Brownian motion. The heat pickup by the nanopar- ticles from the heat source during collision was estimated from MD simulation. This has been coupled with stochastic stimulation to estimate thermal conductivity enhancement. In experiments, the Cu-1% Cr and Cu-3%Cr nanoparticles have been synthesized by mechanical alloying. The measured quantity of synthesized nanoparticles has been dispersed in ethylene glycol using programmed ultrasonication. Different surfactants like sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB) and oleic acid have been used to prepare nanofluids. The effect of particle loading and surfactant concentra- tion on stability of ethylene glycol based nanofluids has been visually studied by TEM and Zeta potential analysis. In the best cases of Cu-Cr dispersed nanofluids was stable for 5 days from the time of synthesis. The thermal conductivity of ethylene glycol based Cu-Cr nanofluid has been measured by transient hot wire method using Flucon LAMBDA equipment. Ó 2020 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of the scientific committee of the 2nd International Conference on Processing and Characterization of Materials. 1. Introduction Heat transfer is one of the most important processes in many industrial and consumer products. The inherently poor thermal conductivity of conventional fluids puts a fundamental limit on heat transfer. However, conventional heat transfer fluids, such as water, ethylene glycol, oil, etc. are not suitable in all of these appli- cations. Based on the fact that heat transfer in suspensions takes place through the interface between the dispersoids and liquid, researchers have tried to enhance the heat transfer rate by using dispersoids with higher surface area-to-volume ratio, i.e., by using particles with reduced size [1–4]. Modern nanotechnology has enabled to produce particles with size less than 100 nm having surface area-to-volume ratio several orders of magnitude larger than millimeter or micrometer-sized particles. Thus, recognizing an opportunity to apply this emerging nanotechnology to the established thermal engineering. The nanofluids can be produced by various combinations of nanoparticles or nanotubes with the base fluids. Choi (1995) first prepared the nanofluid by dispersing nanoparticles into liquid medium [5]. The commonly used base flu- ids are water, ethylene glycol or oil. In order to get stable a nano- fluid with optimum thermal properties, several dispersion techniques have been applied to minimize nanoparticles agglom- eration, such as ultrasonic vibration. 2. Thermal conductivity enhancement in nanofluids Few of the earlier investigations on thermal conductivity enhancement of nanofluids have been carried out that have been given in Table 1: https://doi.org/10.1016/j.matpr.2020.03.330 2214-7853/Ó 2020 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of the scientific committee of the 2nd International Conference on Processing and Characterization of Materials. Materials Today: Proceedings xxx (xxxx) xxx Contents lists available at ScienceDirect Materials Today: Proceedings journal homepage: www.elsevier.com/locate/matpr Please cite this article as: S. Das, V. Karthik, S. K. Pabi et al., Enhancement of thermal conductivity of Cu-Cr dispersed nanofluids according to multiscale modeling, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2020.03.330