Nanocolloids Based on PEG Mixtures with Several Nanoparticles: Experimental Study on Viscosity, Thermal Conductivity, Density and Isobaric Heat Capacity

An original experimental investigation was conducted to characterize the thermophysical behavior of various nanocolloids. These suspensions utilized a binary mixture of PEG 200 and PEG 400 as the base fluid, with dispersed nanoparticles of copper (Cu), silver (Ag), alumina (Al₂O₃), and magnesium oxide (MgO). Comprehensive measurements were performed to ascertain their thermal conductivity, dynamic viscosity, density, and specific heat capacity, facilitating a comparative analysis of their performance attributes. All thermophysical properties were acquired across a temperature range of up to 333.15 K. Viscosity was additionally scrutinized over a broad range of shear rates, up to 264 s⁻¹, and the presence of hysteresis effects was assessed through cyclic thermal loading. Results indicate a marginal increase in viscosity, approximately 10 %, upon nanoparticle integration. Notably, the observed viscosity hysteresis of the nanocolloids closely mirrored that of the PEG mixture. Regarding thermal transport properties, specific heat exhibited enhancements up to 10 %, and thermal conductivity up to 11.1 %, contingent upon the specific nanoparticle material. The study further provides novel correlations and discusses their agreement with existing theoretical and empirical models.