Journal of Energy Storage 55 (2022) 105408 Available online 4 August 2022 2352-152X/© 2022 Elsevier Ltd. All rights reserved. Research Papers Heat storage system for air conditioning purpose considering melting in existence of nanoparticles Z. Li a, b , Hakeem A. Othman c, d , Alia M. Alzubaidi e , Hosam A. Saad f , Yuelei Zhang b , Chenggang Hu b , Abed Saif Alghawli g, * a Faculty of Mechanical Engineering, Opole University of Technology, Opole, 45758, Poland b Hongwei Institute of Innovative Design, Mianyang, Sichuan, 621000, China c Department of Mathematics, AL-Qunfudhah University college, Umm Al-Qura University, Saudi Arabia d Department of Mathematics, Rada'a College of Education and Science, Albaydha University, Albaydha, Yemen e Department of Mathematics, AL-Qunfudhah University College, Umm Al-Qura University, Saudi Arabia f Department of Chemistry, College of Science, Taif University, P.O. Box 11099, Taif 21944, Saudi Arabia g Department of Computer Science, Al-Afaj College of Science and Humanities, Prince Sattam bin Abdulaziz University, Al-Afaj 710-11912, Saudi Arabia A R T I C L E INFO Keywords: PCM Charging Unsteady phase change process MWCNT nanoparticles Melting time FVM ABSTRACT Mixture of MWCNT nanoparticles and paraffn with melting point of 24.5 ◦ C has been utilized for saving the energy inside the ventilating system. The utilized duct for transportation of air has various tubes containing the paraffn and four styles for such obstacles have been presented. Finite volume method for modeling the melting procedure was utilized and validation test based on previous numerical article indicated good accommodation. Temperature of system at t = 0 is 6.5 ◦ C less than 24.5 ◦ C and hot laminar air fow with temperature of 14 K greater than initial temperature makes the paraffn to melt. With adding MWCNT nanoparticles the required time of charging reduce from 7.015 h to 6.74 h when DR = 0.16 which is associated with promising infuence of such particles in augmentation of heat absorption. Moreover, as diameter of tube changes from 9.7 cm to 5 cm, the melting time declines from 6.74 h to 4.12 h. The needed time of process declines around 58.7 % with utilizing smaller tubes in existence of nanoparticles. 1. Introduction Heat energy can be saved in thermochemical, sensible and latent and thermal storage [1–5]. The latent thermal storage in PCMs has more favorable features compared to other thermal storage mechanisms, as PCM has different benefcial properties [6–11]. PCM can be applied as a thermal resource at a fxed temperature with a minimum temperature falls within the thermal recovery [12–16]. It has a great energy capacity with a small storage volume, non-corrosion, low vapor pressure and chemical stability at operating temperature [17–22]. So, paraffn is one of the most effcient ways employed in heat energy storage uses [23–29]. Numerous engineering uses, including electronic cooling technology, ventilation, air conditioning and waste heat recovery are practical to PCM [30–38]. Saving heat in the substances to apply for various goals like generate electricity or saving in battery can be categorized [39–42]. In various renewable energy applications, LHTES by employing PCMs stays widely applied, because of the feature of great energy saving capability and almost the same temperature [43–48]. PCMs are cate- gorized into 4 main groups according to the phase change feature; which are liquid to gas, solid to solid, solid to gas and solid to liquid [49–53]. Solid to solid PCMs cannot save a considerable value of energy than the others [54–59]. Inversely, the leak challenge does not happen in this heat storage systems that are imperative for solid to liquid mechanisms [60–63]. The melting procedure of PCM including tilted fn was conducted by Fekadu et al. [64]. They saw that recognizing the optimum number of fns and using rectangular container can decrease the charging period of paraffn and tilted fns at 45 o can reduce PCM melting period inside a rectangular container at a great rate. The authors of [65] proved that the vertical arrangement obtains slight greater stream strength amounts than the horizontal arrangement within both discharging and charging procedures for medium PCM liquid fraction. An empirical analysis presented by Usman et al. [66] was done on various shapes of a thermal sink. They saw that implanting fns in various styles reduced the base * Corresponding author. E-mail addresses: haoali@uqu.edu.sa (H.A. Othman), amzubidi@uqu.edu.sa (A.M. Alzubaidi), a.alghauly@psau.edu.sa (A.S. Alghawli). Contents lists available at ScienceDirect Journal of Energy Storage journal homepage: www.elsevier.com/locate/est https://doi.org/10.1016/j.est.2022.105408 Received 13 February 2022; Received in revised form 12 July 2022; Accepted 26 July 2022