Flow Boiling Heat Transfer to a Dielectric Coolant in a Microchannel Heat Sink

Abstract

This paper presents an experimental study of flow boiling heat transfer in a microchannel heat sink. The dielectric fluid Fluorinert FC-77 is used as the boiling liquid after it is fully degassed. The experiments were performed at three flow rates ranging from 30 to 50 ml/min. The heat transfer coefficients, as well as the critical heat flux, were found to increase with flow rate. Wall temperature measurements at three locations (near the inlet, near the exit, and in the middle of heat sink) reveal that wall dryout first occurs near the exit of the microchannels. The ratio of heat transfer rate under critical heat flux conditions to the limiting evaporation rate was found to decrease with increasing flow rate, asymptotically approaching unity. Predictions from a number of correlations for nucleate boiling heat transfer in the literature are compared against the experimental results to identify those that provide a good match. The results of this work provide guidelines for the thermal design of microchannel heat sinks in two-phase flow.

Microchannel size effects on local flow boiling heat transfer to a dielectric fluid

“…At higher heat fluxes, as the convective heat transfer starts to dominate, the curves diverge and, as in the single-phase region, more heat is dissipated as mass flux increases at a fixed wall temperature. These trends are also consistent with results in the literature [12,13,14]. The same behavior is observed in all the smaller microchannels for mass fluxes of 700 kg/m 2 s and larger.…”

“…Chen and Garimella [9] compared the boiling heat transfer coefficients and pressure drops for flow rates of 260, 349, and 445 kg/m 2 s. Liu and Garimella [12] carried out an experimental study of flow boiling heat transfer in microchannels (275 μm × 636 μm) cut into a copper block, using DI water with mass fluxes ranging from 341 to 936 kg/m 2 s. Chen and Garimella [13] performed an experimental study of flow boiling of FC-77 in a copper microchannel (10 channels, 405 μm × 2.5 mm) heat sink at flow rates ranging from 80 to 133 kg/m 2 s. Pate et al [14] explored two-phase heat transfer in parallel microchannels with hydraulic diameter of 253 μm using FC-72 as the test fluid. Six re-entrant type cavities, spaced evenly on the base of each channel, were used to promote controlled nucleation.…”

“…Mass fluxes in the range of 535-2138 kg/m 2 s were considered. All these studies [9,12,13,14] showed that beyond the onset of nucleate boiling, the boiling curves collapsed on a single curve for all mass flow rates; as the heat flux was increased further, the curves diverged and became dependent on mass flux. Lin et al [15] performed an experimental study of two-phase flow of refrigerant R141b in circular tubes of diameter of 1.8, 2.8, 3.6 mm and one square tube of 2 × 2 mm 2 with different mass fluxes ranging from 50…”

Review and Comparative Analysis of Studies on Saturated Flow Boiling in Small Channels

“…Many studies have arrived at a similar conclusion with regard to the predominance of the nucleate boiling regime in microchannel flow boiling [26,27,35,40,45,78,53,69,73,79,134].…”

“…Yan and Lin [28] Bao et al [32] Lin et al [29] Agostini et al [31] Saitoh et al [82] Yun et al [33] Qi et al [79] Harirchian and Garimella [74] Chen and Garimella [69,73] Bertsch et al [30] Average over all data sets 24. Bao et al [32] Lin et al [29] Agostini et al [31] Saitoh et al [82] Yun et al [33] Qi et al [79] Harirchian and Garimella [74] Chen and Garimella [69,73] Bertsch et al [30] Average over all data sets -39.…”