Studies on nanoparticle coating due to boiling induced precipitation and its effect on heat transfer enhancement on a vertical cylindrical surface

• Published in: Experimental thermal and fluid science 2012-04, Vol.38, p.229-236
• Main Authors: Hegde, Ramakrishna N., Rao, Shrikantha S., Reddy, R.P.
• Format: Article
• Language: English
• Subjects: Applied sciences; BHT; Boiling; Chemistry; Coating; Colloidal state and disperse state; Condensed matter: structure, mechanical and thermal properties; Cylindrical surface; Energy; Energy. Thermal use of fuels; Exact sciences and technology; General and physical chemistry; Heat transfer; Heaters; Heating equipment; Nanocomposites; Nanofluid; Nanomaterials; Nanostructure; Physical and chemical studies. Granulometry. Electrokinetic phenomena; Physics; Surface roughness; Theoretical studies. Data and constants. Metering; Thermal properties of condensed matter; Thermal properties of small particles, nanocrystals, nanotubes
• ISSN: 0894-1777; 1879-2286
• DOI: 10.1016/j.expthermflusci.2011.12.011

Pool boiling experiments were conducted to study the heat transfer characteristics using low concentrations (0.1–0.5g/l) of Alumina-nanofluid at atmospheric pressure in distilled water. The study involved investigation on the effect of nanoparticle coating on the vertical test surface exposed to multiple heating cycles, heat transfer characteristics of nanoparticle coated surface in distilled water and pool boiling behavior of Alumina nanofluid subjected to transient characteristics. In order to quantify the result, surface roughness of the cylindrical surface was measured at different concentrations of nanofluid before and after the experiments. At atmospheric pressure, different concentrations of nanofluids displayed different degrees of deterioration in boiling heat transfer. Coating of nanoparticles was observed on the heater surface due to boiling induced precipitation. The nanoparticle coated heater when tested in pure water showed significant increase in CHF comparable to CHF of bare heater tested in pure water. Study on transient characteristics of the nanofluid, keeping the heat flux constant for a specified time interval showed degradation in boiling heat transfer. The longer the duration of exposure of the heater surface, the higher was the degradation in heat transfer. Based on the experimental investigations it can be concluded that nanoparticle coating can be a potential substitute for enhancing the heat transfer.