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

Abstract

ABSTRACT

A hierarchical manifold microchannel heat sink array for high-heat-flux two-phase cooling of electronics

“…The heat input required to reach the saturation temperature increases with increasing fluid flow rates, which results in the single-phase regime being extended to higher heat fluxes for deeper channels and larger mass fluxes. It has been observed in the literature that increasing mass flux leads to increased wall superheats at incipience in straight microchannels [39]. This trend is also observed in the current system, where all three samples begin boiling at chip superheats of 8 -10 °C for a mass flux of 1300 kg/m²s and 14 -22 °C for a mass flux of 2900 kg/m²s.…”

Fundamental issues, mechanisms and models of flow boiling heat transfer in microscale channels

“…Just to show two examples here, Figure 15 shows comparison of the experimental data of flow boiling heat transfer coefficient with CO 2 by Yun et al [100] No explanation why there is such a big difference even was offered in their paper. Figure 16 shows the comparison of the CO 2 flow boiling heat transfer coefficients of Pettersen [101] Harirchian and Garimella [65] conducted experiments of flow boiling with FC-77 in multiple rectangular microscale channel heat sinks. They analysed the effect of the mass flow rate and the channel size on the flow boiling heat transfer characteristics in microscale channels with a constant channel depth of 400 µm and different channel widths ranging from 100 µm to 5850 µm.…”

A composite heat transfer correlation for saturated flow boiling in small channels

“…In conventional tubes the heat transfer coefficient at high vapor qualities is usually enhanced in the annular flow regime [38,41,42,44]. For small channels, on the other hand, the enhancement of the heat transfer coefficient with increasing vapor quality is shown to be far smaller [1,9,23,24,45]. The enhancement factor must reduce to 1 for pure liquid and pure vapor, and be greater than 1 within the two-phase regime.…”

“…One of the only correlations that was based on a larger set of minichannel and microchannel heat transfer measurements from several independent sources was due to Thome et al [21,22]. While this correlation is fairly successful over a broad parameter range, its main drawback lies in its assumption of a single heat transfer regime, which conflicts with the observation of multiple flow regimes by several researchers [5,23,24,25] as well as the trends of several heat transfer measurements [14,16,19].…”

“…In recent years, a large number of well-characterized experiments with small channels have been published [13,14,16,[23][24][25][26][27][28][29][30][31][32][33][34][35][36][37]. These studies cover a wide range of operating parameters, fluids and physical dimensions, and present a good database against which to validate existing correlations and to support the formulation of new correlations.…”