Enhancement of critical heat flux using nano-fluids for Invessel Retention–External Vessel Cooling

• Published in: Applied thermal engineering 2012-03, Vol.35, p.157-165
• Main Authors: Pham, Q.T., Kim, T.I., Lee, S.S., Chang, S.H.
• Format: Article
• Language: English
• Subjects: Applied sciences; Boiling; CHF; Contact angle; Cooling; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Heat flux; Heat transfer; IVR; Nano-fluids; Nanocomposites; Nanomaterials; Nanostructure; Orientation; Pool boiling; Roughness; Theoretical studies. Data and constants. Metering; Vessels
• ISSN: 1359-4311
• DOI: 10.1016/j.applthermaleng.2011.10.017

This study investigated the pool boiling critical heat flux (CHF) of water-based nano-fluids under atmospheric pressure for Invessel Retention (IR)–External Vessel Cooling (EVC). The heated surface was a stainless steel foil inclined at different orientation angle from 0° (horizontal downward facing position) to 90° (vertical position). Three working nano-fluids with high suspension stability were selected by the zeta potential method to investigate the effect of each nano-fluid on CHF at the heated surface, which were 0.05% Alumine (Al2O3), 0.05% carbon nanotubes (CNT) + 10% boric acid and 0.05% Al2O3 + 0.05% CNT. It was observed that these nano-fluids enhanced CHF significantly (up to 220%) compared to deionized (DI) water. Furthermore, for all test fluids, CHF increased when the orientation angle increased. The surface characterization after boiling tests shows that the CHF enhancement with nano-fluids can be related to the increase of both surface roughness and wettability caused by nanoparticle deposition during the boiling processes. ▸ Selection of high suspension stability nano-fluids by zeta potential method (0.05% aluminum oxide (Al2O3); 0.05% carbon nanotubes (CNT) + 10% boric acid; and 0.05% Al2O3 + 0.05% CNT). ▸ Nano-fluids enhanced critical heat flux (CHF) significantly (up to 220%) compared to deionized (DI) water. ▸ CHF increased when the orientation angle increased. ▸ CHF enhancement with nano-fluids can be related to the increases of both surface roughness and wettability caused by nanoparticle deposition during the boiling processes.