Thermal conductivity of CuO–DI water nanofluids using 3-ω measurement technique in a suspended micro-wire

There are growing needs to measure the thermal properties using low volume fluid samples in various fields such as biotechnology and nanofluids and there has been significant research toward miniaturization of these measurement device. In this paper, a device that uses 3-ω method for the purpose of thermal conductivity measurement is designed and presented. The 3-ω method requires temperature data in the frequency domain requires relatively smaller sample and power and hence is devoid of transient errors. The sensor is a platinum wire of 50 μm in diameter and 30 mm in length, which is immersed in a cylindrical bore that can accommodate a sample size of 25 μl. The device is validated with de-ionized water with the accuracy between ±0.2% and ±1.2%. Using the device, the thermal conductivity of CuO-deionized water nanofluids is measured for volume fractions of nanoparticles namely 0.025%, 0.05% and 0.1% for temperatures between 15 and 35 °C. An enhancement in thermal conductivity over the base fluid is witnessed for the tested temperature and volume fraction. Finally, the influence of pH ranging including the iso-electric point on the thermal conductivity is also studied and presented.