Effects of Temperature and Particle Size on the Thermal Property Measurements of Al₂O₃−Water Nanofluids

Abstract

An experimental investigation was conducted on the effective thermal conductivity and viscosity of Al2O3 water-based nanofluids. The thermal conductivity was determined using the transient hot wire (THW) method. The results show that the thermal conductivity of Al2O3 nanofluids increases with increasing nanoparticle concentrations in a distinct linear trend. Adding (1 to 5) % of Al2O3 nanoparticles to water increases the effective thermal conductivity of Al2O3 nanofluids by (6 to 20) % at room temperature. There is a substantial increase in the enhancement of thermal conductivity as temperature increases. At 55 °C, this value increases to around 16 %. The thermal conductivity enhancement decreases from (30 to 10) % while the particle size increases from (10 to 35) nm, but enhancement increases when the particle size is above 35 nm. The increase in thermal conductivity is 27.5 % for a particle size of 150 nm. In the viscosity measurements, the effective viscosity increases up to 60 % as the volume concentration increases from 1 % to 5 % at 25 °C. As the temperature increases, the viscosity of Al2O3 nanofluids decreases exponentially. Experimental results also indicate that the viscosity of nanofluids is much higher when the nanoparticle size is smaller.

Viscosity of nanofluids based on an artificial intelligence model

“…Nguyen et al [7] Kwek et al [35] conducted an experimental investigation into the variation in temperature and volume concentration on the viscosity of Al 2 O 3 -water suspensions.…”

Thermal Property Measurement of Al2O3-Water Nanofluids

“…As discussed by Kwek et al (2010), different sizes of the Al 2 O 3 nanoparticles and the surfactant, Cetyltrimethylammonium Bromide (CTAB), were purchased from Sigma Nanoamor and Aldrich respectively. During the experiments, we dispersed the Al 2 O 3 nanoparticles with an average diameter of 25 nm and particle density of 3.7 g/cm 3 into 100 ml of the de-ionized water to prepare the different volume concentrations (1%, 2%, 3%, 4%, and 5%).…”

“…1. Schematics of the THW setup (Kwek et al, 2010). circuit, and a thin platinum wire surrounded by a circular nanofluid container, which is maintained by a thermostat bath.…”

“…This measured unbalanced voltage over the natural logarithm of time was plotted in Fig. 2 by using Equation (2) (Kwek et al, 2010). The thermal conductivity is then calculated from the slope and intersect.…”

A Review and Parametric Investigation Into Nanofluid Viscosity Models

“…The results indicate decreasing relative viscosity values with increasing nanoparticle diameter values for the Graham [43] model while the contrary is the case for the RW [12] model, in which the relative viscosity increases with nanoparticle diameter. Data from the experimental work of Lu and Fan [55], and Kwek et al [56] indicate a drop in the value of g r with increasing d p values. The disparity in the model predictions and the empirical data emphasizes the need to employ functional mechanisms in modeling the viscosity.…”