Assessment of the process of boiling heat transfer during rewetting of a vertical tube bottom flooded by alumina nanofluid. (March 2016)

• Record Type: Journal Article
• Authors: Paul, Gayatri; Das, Prasanta Kumar; Manna, Indranil
• Is Part Of: International journal of heat and mass transfer. Volume 94(2016:Mar.)
• Page Start: 390
• Page End: 402
• Publication Date: 2016-03
• Subjects: Rewetting -- Bottom flooding -- Alumina nanofluid -- Apparent rewetting temperature -- Boiling curve -- Nanoparticle deposition; Heat -- Transmission -- Periodicals; Mass transfer -- Periodicals; Chaleur -- Transmission -- Périodiques; Transfert de masse -- Périodiques; Electronic journals; 621.4022
• DOI: 10.1016/j.ijheatmasstransfer.2015.11.013
• Languages: English
• ISSNs: 0017-9310

Abstract

Highlights: Rewetting phenomenon of vertical tubes by bottom flooding is investigated. Rewetting takes place earlier in case of alumina dispersed nanofluids than water. Rewetting temperature and boiling curves are estimated from temperature transients. Concentration of particles and coolant velocity strongly affects rewetting process. While using nanofluids, the deposition of nanoparticles augments heat transfer rate. Abstract: The present investigation focusses on the rewetting of a vertical tube bottom flooded by alumina dispersed water nanofluids. Emphasis is on the estimation of the apparent rewetting temperature and most importantly the construction of boiling curve from the temperature–time responses recorded during the rewetting phenomenon. The boiling curves provide an insight into the different regimes of boiling under flow conditions. Rewetting in nanofluids takes place faster than water. Rewetting in general, depends on coolant inlet velocity, initial wall temperature and axial location of the tube from the inlet. For nanofluids, it also depends on the concentration of nanoparticles. An earlier rewetting and an enhanced maximum heat flux exhibited by nanofluids can be attributed to the deposition of nanoparticles which results in the formation of several micro-cavities. This in turn alters the surface wettability and roughness, thereby inducing an enhanced rate of heat transfer and an earlier collapse of vapor film. The deposition of nanoparticles and its morphology, confirmed from microscopic and spectroscopic analysis, supports this conjecture.