Convective Heat Transfer and Stability of Oil –Based Nanofluid

Objectives: Design and building a dedicated device (test rig) for measuring the convective heat transfer coefficient for an oil – based nanofluid under a laminar flow regime and a uniform heat flux. Preparing a stable oil – based nanofluid. Measuring experiment the stability of oil – based on nanofluid. Methods/Statistical Analysis: The nanofluid was prepared via two steps method, with three different mixing processes. Lubricating oil was used as a host liquid with aluminum oxide (Al2O3) as nanoparticles, with two particle sizes of 80 nm and 30 nm and different concentrations of (0.2, 0.6, 1 and 2) %wt. In order to study the effect of nanofluids on heat transfer coefficient, a dedicated test rig designed and built consisting of horizontal copper pipe, oil gear pump, nanofluid tank, heater and heat exchanger as a major components of the rig in addition of the accessory components and measuring devices.The stability of the nanofluid measured experimentally with Zeta Potential Analyzer. Findings: The heat transfer coefficient increased with increasing of the particle loading and decrease the particle size, the maximum enhancement in heat transfer coefficient at 2% wt was (7.83% and 16.75%) for 80 nm and 30 nm particle sizes, respectively. The best stability was found to be with 30 nm particle size at lower particle loading of (0.2% wt) and this concentration was recommended to use due to the excellent stability, lower cost and almost unnoticeable increasing in pressure drop. The nanofluid stability decreases with increasing both the particle size and particle loading. Application/Improvements: The base fluid of the used nanofluids is lubricating oil of automobile engine and the study showed an enhancement in the heat transfer coefficient with small penalty in pressure drop especially for the samples of low concentration and smallest particle size.