Experimental investigation on thermophysical properties of ethylene glycol based copper micro- and nanofluids for heat t
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Experimental investigation on thermophysical properties of ethylene glycol based copper micro- and nanofluids for heat transfer applications
Nader Nikkam1 , Morteza Ghanbarpour2 , Rahmatollah Khodabandeh2 , Muhammet S. Toprak1 * 1 Department of Materials and Nano Physics, KTH- Royal Institute of Technology, SE-16440 Kista, Stockholm, Sweden. 2 Department of Energy Technology, KTH- Royal Institute of Technology, SE-100 44 Stockholm, Sweden ABSTRACT The present work reports on the fabrication, experimental and theoretical investigation of thermal conductivity (TC) and viscosity of ethylene glycol (EG) based nanofluids/microfluids (NFs/MFs) containing copper nanoparticles (Cu NPs) and copper microparticles (Cu MPs). Cu NPs (20-40 nm) and Cu MPs (0.5-1.5 μm) were dispersed in EG with particle concentration from 1 wt% to 3 wt% using powerful ultrasonic agitation, and to study the real impact of dispersed particles the use of surface modifier was avoided. The objectives were to study the effect of concentration and impact of size of Cu particles on thermo-physical properties, including thermal TC and viscosity, of EG based Cu NFs/MFs. The physicochemical properties of NPs/MPs and NFs/MFs were characterized by using various techniques. The experimental results exhibited higher TC of NFs and MFs than the EG base liquid. Moreover, Cu NFs displayed higher TC than MFs showing their potential for use in some heat transfer applications. Maxwell effective medium theory as well as Einstein law of viscosity was used to compare the experimental data with the predicted values for estimating the TC and viscosity of Cu NFs/MFs, respectively. INTRODUCTION There is a strong need in cooling industry to develop heat transfer fluids with improved thermal characteristics. Since the solid particles have higher TC than conventional heat transfer fluids, such as water or EG, suspensions containing solid particles can be a reasonable choice to use as heat transfer fluids. Dispersions containing micrometer size particles (MFs) have already been used to enhance the thermal characteristics of base liquids [1]. Recently, nanofluids (NFs) [2], new suspensions containing nanoscale particles, have attracted attention due to their potential to improve thermal properties of conventional heat transfer fluids such as water or EG. So far we have studied and reported on a wide range of materials and base liquids of NFs/MFs for heat transfer applications including: mesoporous SiO 2 [3], Cu NP/MP [4-5], CNTs [6], Al2 O3 , ZrO2 and TiO 2 [7], CeO 2 [8], and SiC [9-10]. Mainly two methods are used to fabricate NFs/MFs: One-step method where particles are directly formed in the base liquid [4], while in the two-step method particles are synthesized, dried and then dispersed in the base liquids [5]. Many factors such as particle morphology (size and shape), particle concentration, NF/MF preparation method, surface modifier and base liquid can affect the TC and viscosity of NFs/MFs [11-12]. There are very few systematic studies related to the impact of particle si
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