Molecular dynamics simulation of the thermal properties of the Cu-water nanofluid on a roughed Platinum surface: Simulation of phase transition in nanofluids Nidal H. Abu-Hamdeh a , Eydhah Almatrafi b , M. Hekmatifar c , D. Toghraie c, ⁎, Ali Golmohammadzadeh c a Center of Research Excellence in Renewable Energy and Power Systems, and Department of Mechanical Engineering, Faculty of Engineering, King Abdulaziz University, Jeddah 21589, Saudi Arabia b Mechanical Engineering Department, Center of Excellence in Desalination Technology, King Abdulaziz University, P.O. Box 80200, Jeddah 21589, Saudi Arabia c Sapienza Università di Roma, Via Eudossiana 18, Roma 00184, Italy abstract article info Article history: Received 31 October 2020 Received in revised form 11 November 2020 Accepted 19 November 2020 Available online xxxx Keywords: Atomic barrier Molecular dynamics simulation Thermal behavior Argon Nanofluid Phase transition Copper Thermal conductivity Barrier size influences on the thermal behavior of Ar/Cu nanofluid are reported in this simulation work. Molecular dynamics method is implemented with a large molecular/atomic parallel simulator. Furthermore, Ar/Cu nanofluid is simulated with Universal Force Field (UFF) and Embedded Atom Model (EAM) force fields and these force fields are appropriate to our thermal study. For the thermal behavior of this nanofluid, we record the physical parameters like total energy, thermal conductivity of nanofluid, density, the number of nanofluid atoms in the gas phase, and atomic temperature. Simulation results show that atomic structures have thermal stability with −318 eV value for total energy parameter. Physically, the atomic barrier causes the atomic phase transition phenomena to happen in a shorter time. Numerically, this parameter varies from 0.61 ns to 0.55 ns when the Platinum (Pt) barriers height increases from 5 Å to 10 Å. We calculated that the maximum density of nanofluid atoms reaches to 0.00025 Atom/Å 3 by atomic barriers enlarging. So, we conclude that, by increasing the received heat flux with Ar/Cu nanofluid, the thermal conductivity converged in shorter simulation time. Nu- merically, the thermal conductivity of simulated structures converges to 0.016400 W/m.K after 0.63 ns. © 2020 Elsevier B.V. All rights reserved. 1. Introduction In many industrial processes, heat energy is removed/added from one method to another, and it is become an important procedure in modern essentials. These mechanisms provide process fluid cooling or heating cycle and a source for energy recovery [1–5]. The improvement of cooling/ heating in industrial applications create a saving and pre- serving in energy, reduces process time, optimize thermal behavior, and raise the performance of the apparatus. Some thermal mechanisms are influenced by enhancing the heat transfer rate [6–10]. Numerous re- searches have been done to achieve a comprehension of the heat trans- fer mechanism for their specific aims to heat energy transfer optimization [11–16]. Nanofluid is a right sort of heat energy transfer structure concluding Nano-size fractions between 1 nm to 100 nm, which are uniformly dispersed in various base-fluids [17–20]. However, because of the difference of these atomic structures, no agreement has been achieved on the magnitude of potential advantage of using these nanostructures for heat transfer aims. Historically, Choi classified a promising class of fluids for the first time [21,22]. Choi et al. [23] could measure the thermal conductivity of CNT. They expressed that the ther- mal conductivity of the base-fluid growth appreciably (200% approxi- mately). Ahammed et al. [24] estimated the thermal conductivity of water/graphene nanofluid in difference temperatures. Selvam et al. [25] research about the water-based graphene fluids and ethylene gly- col. They expressed that the thermal behavior enhancement of these nanostructures raised. Ding et al. [26] investigated about the thermal behavior of CNT/ water nanofluid; they said that the optimization of the thermal be- havior was closed to 350%. Akhavan et al. [27] reported the transport coefficients related to graphene/water nanofluid. Witharana et al. [28] and Chen et al. [29] showed that the nanoparticles are an impor- tant parameter for thermal conductivity improves of base-fluids. Fur- thermore, in previous researches, phase transition related to base- fluid was changed [30]. In addition to experimental researches, theoretical methods such as Molecular Dynamics (MD) approach can be used. This computational approach is widely implemented in the thermal and atomics manner study of nanostructures [31–37]. Atomic barriers effect on thermal con- ductivity of fluid and nanofluids were studied effectively by this Journal of Molecular Liquids xxx (xxxx) xxx ⁎ Corresponding author. E-mail addresses: nabuhamdeh@kau.edu.sa (N.H. Abu-Hamdeh), ealmatrafi@kau.edu.sa (E. Almatrafi), davoodtoghraie@yahoo.com, Toghraee@iaukhsh.ac.ir (D. Toghraie). MOLLIQ-114832; No of Pages 7 https://doi.org/10.1016/j.molliq.2020.114832 0167-7322/© 2020 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Journal of Molecular Liquids journal homepage: www.elsevier.com/locate/molliq Please cite this article as: N.H. Abu-Hamdeh, E. Almatrafi, M. Hekmatifar, et al., Molecular dynamics simulation of the thermal properties of the Cu- water nanofluid on a roughed Plati..., Journal of Molecular Liquids, https://doi.org/10.1016/j.molliq.2020.114832