Critical Heat Flux During Flow Boiling in Mini and Microchannel-a State of the Art Review

Abstract

A state of the art review of critical heat flux during flow boiling through mini and microchannels has been provided based on the open literature. This review mainly examines three aspects, namely the experimental investigations, the available correlations and the state of prediction using those correlations and finally the proposed physical mechanisms as well as the theoretical models. Before discussing the specific literature on microchannels, a brief overview of critical heat flux for pool and flow boiling is provided. The review has been concluded with a summary of the available information on this topic and the need for future research.

Surface Structure Enhanced Microchannel Flow Boiling

“…Two-phase microchannel heat sinks are attractive to cool advanced electronic devices because they harness the latent heat of vaporization to dissipate high heat fluxes in a compact form factor. However, minimizing flow instabilities during boiling while enhancing the critical heat flux (CHF) to maximize heat dissipation has been difficult to achieve [4][5][6]. These flow instabilities which can be triggered by several mechanisms including explosive bubble expansion [7], upstream compressibility [8,9] and density wave oscillation [10] can lead to large pressure drop fluctuations across the channels and temperature spikes associated with liquid dry-out.…”

Critical Heat Flux in Flow Boiling in Microchannels

“…Very recent and important experimental investigations are given in Table 2.1 [26]. In case of microtubes; both single and multiple tubes have been used [27][28][29][30][31].…”

“…In this section, the correlations for the CHF in microchannels have been examined. Table 2.2 provides a compilation of correlations relevant for the CHF in microchannel [26]. Critical heat flux varies proportionally with the mass velocity and the enthalpy needed for vaporization [37][38][39][40].…”

“…Figures 1.1 , 1.2 , 1.3 , 1.4 and 1.5 show the heat transfer mechanisms and systems for fl ow boiling in microchannels [ 5 ]. The data of Huo et al [ 25 ], Shiferaw et al [ 26 ] and Chen et al [ 27 ] show that, data from the same experimental set up may vary for different observations. E o = 1.6 proposed in [ 28 ] is not always the transition criterion from macroscale to microscale.…”

Assessment of Annular Flow Boiling in the Context of Computational Fluid Dynamics (Cfd) Simulations, Experiments, and Existing Correlations

“…Above this critical heat-flux value, the flow displays instabilities which may result in time varying dry spots on the heating surface (typically experiencing higher qualities) or, in some cases, it may lead to inverted annular flow where the flow has liquid flowing in the core region -with vapor flowing in the annulus region. See [9][10][11] etc.…”