Ronghua Hong

The interface effect of carbon nanotube suspension on the thermal performance of a two-phase closed thermosyphon

An aqueous solution of carbon nanotubes, treated by a concentrated nitric/sulfuric acid mixture to disentangle the nanotubes, was utilized as the working medium in a two-phase closed thermosyphon to investigate its performance. In comparison with the thermosyphon filled with a distilled water medium, the one filled with carbon nanotube suspension has a high evaporation section wall temperature, incipience temperature, and excursion, as well as thermal resistance. The carbon nantotubes’ nanofluid deteriorates the performance of the gravity-assisted heat pipe. Measurements employing the maximum bubble pressure method demonstrate that suspending carbon nanotubes in bulk water gives rise to increased surface tension. In addition, the contact angle of suspension obtained with the sessile drop method on a copper plate is much smaller than that of water. Alterations of solid-liquid-vapor interfacial properties, arising from the addition of carbon nanotubes, change the boiling mechanism and thus deteriorate the b...

Characteristic boiling curve of carbon nanotube nanofluid as determined by the transient calorimeter technique

Nickel-plated copper sphere is employed as the transient calorimeter to explore the boiling heat transfer characteristics of carbon nanotube (CNT) nanofluid. As compared to water, aqueous gum arabic (GA) solution has an enhanced critical heat flux (CHF), transition boiling, and minimum heat flux in film boiling (Leidenfrost point). CNT nanofluid has higher CHF than GA solution. Better wettability and deposits on the heating surface distort the characteristic boiling curve.

Enhanced Critical Heat Flux During Quenching of Extremely Dilute Aqueous Colloidal Suspensions With Graphene Oxide Nanosheets

In this Technical Brief, we report on preliminary results of an experimental investigation of quenching of aqueous colloidal suspensions with graphene oxide nanosheets (GONs). Extremely dilute suspensions with only 0.0001% and 0.0002% (in mass fraction) of GONs were studied and their critical heat fluxes (CHF) during quenching were determined to increase markedly by 13.2% and 25.0%, respectively, as compared to that of pure water. Such efficient CHF enhancement was interpreted to be caused primarily by the improved wettability of the quenched surfaces, due to deposition of the fish-scale-shaped GONs resulting in self-assembly quasi-ordered microscale morphologies.