Micromachines 2022, 13, 1871. https://doi.org/10.3390/mi13111871 www.mdpi.com/journal/micromachines Article Performance of Air-Conditioning System with Different Nanoparticle Composition Ratio of Hybrid Nanolubricant Nurul Nadia Mohd Zawawi 1 , Wan Hamzah Azmi 1,2, *, Mohd Fairusham Ghazali 1,2 and Hafiz Muhammad Ali 3,4 1 Center for Research in Advanced Fluid and Processes, Universiti Malaysia Pahang, Lebuhraya Tun Razak, Kuantan 26300, Malaysia 2 Faculty of Mechanical and Automotive Engineering Technology, Universiti Malaysia Pahang, Pekan 26600, Malaysia 3 Mechanical Engineering Department, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia 4 Interdisciplinary Research Center for Renewable Energy and Power Systems (IRC-REPS), King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia * Correspondence: wanazmi2010@gmail.com; Tel.: +6-09-4316223 Abstract: To reduce fuel consumption, the automotive air-conditioning (AAC) system’s coefficient of performance (COP) needs to be improved. The use of a diverse selection of hybrid nanolubricant composition ratios is expected to improve the properties of single nanolubricants, resulting in im- proved AAC system performance. The goal of this study was to find the best combination of hybrid nanolubricants for the best performance of the AAC system. Al2O3-SiO2/PAG hybrid nanolubricants at 0.06% volume concentrations with various composition ratios (20:80, 40:60, 50:50, 60:40, and 80:20) were investigated. An initial refrigerant charge of up to 155 g and a compressor speed of up to 2100 rpm were used in the experiment. The cooling capacity, compressor work, and COP of the AAC system were measured to determine its efficiency. The COP enhancement and compressor work reduction were recorded up to 16.31% and 18.65% for the 60:40 composition ratio, respectively. The maximum cooling capacity up to 75.84% was recorded for the 80:20 ratio, followed by 60:40. The maximum COP value of 8.81 for 155 g of hybrid nanolubricants was obtained at 900 rpm with a 60:40 composition ratio. Therefore, for optimal performance in the AAC system, a 60:40 composition ratio of the Al2O3-SiO2/PAG nanolubricant combination is strongly recommended. Keywords: hybrid nanolubricants; composition ratios; PAG; air-conditioning; refrigeration system 1. Introduction In today’s society, an air-conditioning system in a vehicle is a necessary and indis- pensable piece of technology [1] as it is used to provide vehicular thermal comfort for the driver and passenger. The effect of cooling the passenger compartment on the vehicle energy consumption and emissions is highly dependent on the thermal comfort [2] in real conditions. There are a few issues with the current automotive air-conditioning (AAC) system including the fact that it increases fuel consumption while cooling the compart- ments to the desired level of thermal comfort [3,4]. First, vehicles are in a low-efficiency region when operating with the air-conditioning system during idle conditions for an ex- tended period of time [5]. Consequently, increments in the workload, power, and fuel consumption of the vehicles are required to maintain the operation of the AAC system. The next issue is the increase in harmful gasses emitted by vehicles such as carbon dioxide (COx), hydrocarbons (HC), nitrogen oxides (NOx), and carbon monoxide (CO) [6,7] during idling and slow moving traffic. The gases released into the atmosphere will cause air pol- lution [8] and increase the average temperature on Earth. Therefore, these issues are being Citation: Zawawi, N.N.M.; Azmi, W.H.; Ghazali, M.F.; Ali, H.M. Performance of Air-Conditioning System with Different Nanoparticle Composition Ratio of Hybrid Nanolubricant. Micromachines 2022, 13, 1871. https://doi.org/10.3390/ mi13111871 Academic Editors: Tianzhuo Zhan, Mengjie Song, Yanguang Zhou and Yen-Ju Wu Received: 21 September 2022 Accepted: 26 October 2022 Published: 30 October 2022 Publisher’s Note: MDPI stays neu- tral with regard to jurisdictional claims in published maps and institu- tional affiliations. Copyright: © 2022 by the authors. Li- censee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and con- ditions of the Creative Commons At- tribution (CC BY) license (https://cre- ativecommons.org/licenses/by/4.0/).