Investigation of the Effects of pH Scale and Ultrasonic Waves on the Stability of Copper Oxide Nanoparticles in the Pool Boiling Process

In this study, the effects of pH and ultrasonic waves on the performance and stability of CuO have been studied. The CuO nanofluid (deionized water-based) was used to increase the boiling heat transfer coefficient. Boiling heat transfer coefficient of fluid increased by the addition of nanoparticles into the fluid, but due to the instability of nanoparticles by increasing temperature and time, nanoparticles were precipitated on the heat transfer surface. Therefore, it led to a reduction in the boiling heat transfer coefficient. Moreover, it is necessary to obtain the optimal concentration of nanoparticles in the fluid to determine the minimum amount of deposition. The use of methods to reduce the deposition of nanoparticles such as increasing the stability of nanoparticles and also an optimal concentration made an increase in heat transfer coefficient. To overcome this challenge, two conventional methods were employed including pH change (9.5, 10 and 10.5) and ultrasonic radiation (with 25%, 50%, and 75% of power). The results indicated that the maximum enhancements of boiling heat transfer coefficient were achieved at nanoparticles concentration of 0.125% under ultrasonic radiation with 50% power and the pH value of 10 as average of 37.48% and 22.68%, respectively.