Proceedings of the 15th International Heat Transfer Conference, IHTC-15 August 10-15, 2014, Kyoto, Japan IHTC15-8604 *Corresponding Author: Mohsen.Sharifpur@up.ac.za 1 INVESTIGATION INTO THE pH AND ELECTRICAL CONDUCTIVITY ENHANCEMENT OF MgO – ETHYLENE GLYCOL NANOFLUIDS Saheed A. Adio, Mohsen Sharifpur Q Q S Josua P. Meyer Nanofluids Research Laboratory, Thermofluids Research Group, Department of Mechanical and Aeronautical Engineering, University of Pretoria, Private Box 0002, Pretoria, South Africa. ABSTRACT The revolution of the industrial and manufacturing sector witnessed with the design and production of high capacity, compact size, portable and light weight devices such as microelectronics and transportation systems is currently posing a critical challenge of thermal management. In order to maintain the compactness of these devices, the conventional method of increasing surface area of heat exchangers by extended surfaces is often ruled out. Recently, researches on the option of using nanofluids as alternative thermal fluids without necessarily increasing the size of heat transfer devices are increasing. However, the issue of its stability is still of a great concern. Actually, stability is essential to the development of technologies that will thrive with the use of this newly formulated heat transfer fluid. Systematic studies on these fluids have shown that pH and electrical conductivity are two interrelated properties which are critical and essential because of their key roles on their stability status. Nevertheless, there has been no detailed research on the pH and electrical conductivity enhancement regarding the ultrasonication energy, temperature variation, nanoparticles size and volume fraction (especially pH). Therefore, in the present work, three different sizes (20, 40 and 100 nm) of MgO nanoparticles at volume fraction up to 2% were prepared using ultrasonication assisted two-step method for 30 and 60 minutes respectively. The pH and electrical conductivity of the prepared samples were studied between the temperature ranges of 20–70 o C. From the available results, the pH and electrical conductivities of MgO-EG nanofluids strongly depend on temperature and volume fraction. On the contrary, it was established that MgO nanoparticles size does not have control on the measured pH and electrical conductivity. However, the patterns obtained were the same for the two ultrasonication times which does not only serve to show the effect of ultrasonication time but also buttresses the repeatability and correctness of the results in this case. It was also found that as low as 0.1% volume fraction produces pH enhancement above 40% and electrical conductivity more than 3000%. KEY WORDS: Thermophysical properties, Nano/Micro scale measurement and simulation, pH enhancement, electrical conductivity, nanofluids, ethylene glycol, nanoparticle 1. INTRODUCTION Industrial techniques and technological advancement are continually being tailored towards sustainable development. This is witnessed in modern manufacturing techniques and devices such as can be found in the microelectronics industries, transportation industries, MEMS and NEMS. The associated thermal management challenges with these new/emerging techniques and devices are very crucial and need urgent attention. In the recent decades, nanofluids have been proposed for use as alternative heat transfer fluid in these devices because conventional heat transfer fluids such as water, engine oil, ethylene glycol etc. have characteristically poor thermal properties. The use of extended surfaces is also often ruled out mainly because it increases the size of the equipment. However, there are still challenges with the use of this newly