Journal Published Online: 01 May 2012
Volume 9, Issue 5

Flow Visualization, Critical Heat Flux Enhancement, and Transient Characteristics in Pool Boiling Using Nanofluids

CODEN: JAIOAD

Abstract

This paper presents the experimental outcome of a study of the pool boiling heat transfer characteristics of alumina and CuO nanofluid in distilled water using a 0.19 mm diameter NiCr wire. A series of experiments were conducted in order to visualize the flow, critical heat flux (CHF) enhancement, and transient characteristics of nanofluid. The boiling phenomenon was visualized using a 0.1 g/l concentration of alumina nanofluid. The average bubble diameter was measured and was found to increase with increased heat flux. The average bubble contact angle decreased from 69° during the initial stages of boiling to 33° at CHF. Massive vapour bubbles were observed on the test heater surface near the CHF, inducing vapour blankets and forming hot/dry spots. The increase in the CHF could be well explained by the hot/dry spot theory. Pool boiling experiments conducted using low volume concentrations of CuO-water nanofluid at atmospheric pressure in distilled water showed an increase in the CHF by 30 % at a 0.3 g/l concentration. The transient behaviour of nanofluid, examined by exposing the heater surface at a constant heat flux of 700 kW/m2, indicated CHF enhancement of 5.21 % to 6.77 % for the two time durations. Based on the experimental investigations, it was concluded that the CHF enhancement is due to nanoparticle coating, which changes the thickness of the surface as a function of time and surface wettability and corroborates the hot/dry spot theory.

Author Information

Hegde, Ramakrishna
National Institute of Technology, Surathkal, IN
Rao, Shrikantha
Dept. of Mechanical Engineering, National Institute of Technology, Surathkal, IN
Reddy, R.
Reva Institute of Technology, Yelahanka, Bangalore, IN
Pages: 16
Price: $25.00
Related
Reprints and Permissions
Reprints and copyright permissions can be requested through the
Copyright Clearance Center
Details
Stock #: JAI104443
ISSN: 1546-962X
DOI: 10.1520/JAI104443