Flow Boiling Heat Transfer and Two-Phase Flow Instability of Nanofluids in a Minichannel

Abstract

Single-phase convective heat transfer of nanofluids has been studied extensively, and dif ferent degrees of enhancement were observed over the base fluids, whereas there is still debate on the improvement in overall thermal performance when both heat transfer and hydrodynamic characteristics are considered. Meanwhile, very few studies have been devoted to investigating two-phase heat transfer of nanofluids, and it remains inconclu sive whether the same pessimistic outlook should he expected. In this work, an experimen tal study of forced convective flow boiling and two-phase flow was conducted for Al20 3-water nanofluids through a minichannel. General flow boiling heat transfer char acteristics were measured, and the effects of nanofluids on the onset of nucleate boiling (ONB) were studied. Two-pliase flow instabilities were also explored with an emphasis on the transition boundaries of onset of flow instabilities (OFl). It was found that the presence of nanoparticles delays ONB and suppresses OFl, and the extent is correlated to the nanoparticle volume concentration. These effects were attributed to the changes in available nucleation sites and sin face wettability as well as thinning of thermal boundary layers in nanofluid flow. Additionally, it was observed that the pressure-drop type flow instability prevails in two-phase flow of nanofluids, but with reduced amplitude in pressure, temperature, and mass flux oscillations.ALO^-water nanofluids with two nanoparticle volume concen trations (0.01 vol. % and 0.1 vol. %) were used in this work. They were prepared following the same method described in Ref.[40], Journal of Heat Transfer

Boiling heat transfer of nanofluids: A review of recent studies

“…Yet, there are a group of researchers interested in presenting other sub-phenomena, such as flow boiling instabilities, bubble formation and flow patterns regarding flow boiling heat transfer of nanofluids. Yu et al [51], for instance, conducted an experimental study on forced convective flow boiling and two-phase flow of Al 2 O 3 -water nanofluids through a mini-channel. They were studying the effects of nanofluids on the onset of nucleate boiling (ONB) and two-phase flow instabilities with an emphasis on the transition boundaries of onset of flow instabilities (OFI).…”

Experimental studies of flow boiling heat transfer by using nanofluids

“…Also, in the case of using nanoparticles with dilute concentration, bubble size was smaller, but bubble density is found to be more with the same heat flux applied to water. Yu et al [64] conducted an experimental study of forced convective flow boiling and two-phase flow of CHF of flow boiling using NFs Fig. 15 Parameters and subphenomenon influence the HTC and CHF during flow boiling heat transfer using nanofluids Al 2 O 3 -water nanofluids through a mini-channel.…”

Determination of the heat transfer coefficient from IRT measurement data using the Trefftz method

“…Process of flow boiling in small channel was susceptible for various kinds of instability than in traditional size channels. In [2] the two-phase flow instability of nanofluids in a minichannel have been presented.…”