The CueH2O nanofluids was prepared through two-step
method (Cu nanoparticle, the average diameter is about 25 nm
and 50 nm, supplied by Shanghai ChaoWei Nanotechnology Co.
Ltd., China; the base fluid is deionized water). A certain amount of
nanopowders were blended with deionized water, and some
dispersing agents (SDBS) were added, then adjusted the pH value of
nanofluids to 8 by HCl and NaOH in analytical grade. The suspension
were stirred 30 min by magnetic stirring apparatus and
oscillated 40 min through ultrasonic oscillation apparatus at 90 W
(KQ2200DE, Kunshan of Jiangsu Equipment Company, China).