Experimental Investigation of Critical Heat Flux in Microchannels for Flow-Field Probes

Abstract

Critical heat flux (CHF) of water in circular stainless steel microchannels with inner diameters ranging from ∼127μm to ∼254 μm was investigated. Forty-five CHF data points were acquired over mass velocities ranging from 1,200 kg/m2s to 53,000 kg/m2s, heated lengths from 2 cm to 8 cm, and exit qualities from −0.2 to 0.15. Most of the exit qualities fell below 0.1. It was found that CHF conditions were more dependent on mass velocity and heated length than on exit thermal condition. The results were also compared to six CHF correlations, with a mean average error ranging from 22% to 261.8%. A new correlation was proposed to better predict the critical heat flux data under the thermal-hydraulic conditions studied in this investigation. In developing the correlation, 319 data points were added from two previous studies.

Scale effects on flow boiling heat transfer in microchannels: A fundamental perspective

“…2 and 3, which are drawn for G ¼ 200 and 1000 kg/m 2 s, respectively. Such high mass fluxes have been investigated in literature; for example the highest mass flux employed by Steinke and Kandlikar [29] with water was 1782 kg/m 2 s, and recently Kosar et al [30] employed extremely high mass fluxes up to 53,000 kg/m 2 s in circular microchannels ranging from 127 to 254 mm in diameter in their CHF studies. It is seen that as the mass flux increases, the relative importance of inertia goes up significantly, while shear forces also become larger.…”

Boiling heat transfer enhancement in mini/microtubes via polyhydroxyethylmethacrylate (pHEMA) coatings on inner microtube walls at high mass fluxes

“…An increase in the velocity of bubbles with respect to the fluid and more dominant condensation effects due to the subcooled fluid bulk in smaller channels are possible explanations [35]. In addition, the heated length over diameter ratio could be relatively large, and emerging bubbles could occupy a significant portion of the tube cross-section [23,36,37], which significantly affects the liquid supply to the heated wall and the flow morphology inside the tube resulting in a more dominant effect of diameter on CHF compared to the conventional size channels. Indeed, the CHF value was observed to be three times larger for the smallest tested microtube compared to the largest tested microtube.…”

History, Advances, and Challenges in Liquid Flow and Flow Boiling Heat Transfer in Microchannels: A Critical Review

“…On the other hand, specific correlations have been developed in the literature based on the researchers' own experimental data, e.g., Refs. [170,173,174,176,177]. They are able to correlate the parent data set well but generally do not fare as well with other data sets.…”