Affiliations: Department of Mechanical Engineering, University of
Minnesota, 111 Church Street SE, Minneapolis, MN 55455, USA | Division of Mechanical Engineering, Ajou University,
Wonchon-Dong, Suwon, 443-749, Korea | Division of Mechanical Engineering, Ajou University,
Wonchon-Dong, Suwon, 443-749, Korea. E-mail: hyunkim@ajou.ac.kr
Abstract: The characteristics of boiling and critical heat flux (CHF) behavior
of nano-fluids with alumina and silver nano-particles suspended in de-ionized
water (pure water) were studied with circular plate heaters in the present
study. Enhancements of CHF in nano-fluids in the wide range of particle sizes
and concentrations were compared with those in pure water. Also, the effects of
the particle deposition on CHF enhancement were investigated. All experiments
were performed at the atmospheric pressure condition. The results show that the
measured boiling curves in nano-fluids were shifted to the right and CHF were
significantly enhanced for different nano-particle sizes and concentrations.
The CHF of nano-fluids was increased as the size of the nano-particles
decreased. On the other hand, nano-particle concentration value showing the
maximum CHF had a critical value. In each pool boiling experiment of
nano-fluids, nano-particles were deposited on the heater surface. Assuming that
this phenomenon caused the CHF enhancement, pool boiling experiments of pure
water were carried out with these nano-particle deposited heaters. The results
of these tests were similar to those of the test of the nano-fluids for the CHF
enhancement. The main cause of CHF enhancement was found to be the change of
the heater surface structure. In order to analyze boiling phenomena of pure
water and Al2O3 nano-fluids, boiling process was visualized by using a high
speed camera.
Keywords: CHF, Nano-particle deposition, Superheat, Nano-fluids, Pool boiling
