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Rheological Behaviour of SiO2/PAO Nanolubricant for an Electric-Driven Compressor Automotive Air-Conditioning System

Muhammad Aminullah Abdul Rahman , Wan Hamzah Azmi , Anwar Ilmar Ramadhan

Published
July 29, 2026

Vol. 9 No. 2 (2026)
Pages 598-611

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Abstract

Compressor lubricants play a crucial role in refrigeration systems by controlling friction, sealing effectiveness, and heat removal, with lubricant viscosity a key parameter that affects hydrodynamic losses and energy efficiency. This study aimed to systematically characterise the rheological behaviour of silicon dioxide/polyalphaolefin (SiO₂/PAO) nanolubricants under compressor operating conditions. SiO₂/PAO nanolubricants with concentrations of 0.01–0.03% were prepared using a two-step method without the use of surfactants, and dynamic viscosity measurements were conducted over a temperature range of 25 to 100 °C and shear rate from 549 to 4320 s⁻¹. The experimental data were further used to understand the viscosity trends under thermal and shear conditions. Both PAO lubricant and SiO₂/PAO nanolubricants exhibited Newtonian rheological behaviour. The incorporation of SiO₂ nanoparticles led to controlled, concentration-dependent changes in viscosity. The 0.01% SiO₂/PAO nanolubricant exhibited the smallest viscosity change (0.7%) even at high temperatures and shear rates, compared with higher concentrations. The findings show that low-concentration SiO₂/PAO nanolubricants, especially at 0.01%, offer good rheological stability with minimal viscosity penalty, providing an advantage to the electric-driven compressor automotive air-conditioning system (EDC-AAC) by reducing compressor work by 3.5%.

Keywords

SiO₂ nanoparticles; PAO; Nanolubricants; Rheological; Electric compressor; Automotive Air Conditioning

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Published July 29, 2026
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Copyright Copyright (c) 2026 A.R.M. Aminullah, W.H. Azmi, Anwar Ilmar Ramadhan
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Keywords
  • SiO₂ nanoparticles
  • PAO
  • Nanolubricants
  • Rheological
  • Electric compressor
  • Automotive Air Conditioning

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