Heat transfer correlation for boiling flows in small rectangular horizontal channels with low aspect ratios

Lee, Han Ju; Lee, Sang Yong

doi:10.1016/s0301-9322(01)00054-4

Cited by 283 publications

(105 citation statements)

References 19 publications

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“…It was shown that the saturated flow boiling heat transfer coefficient in a microchannel heat sink is a strong function of mass velocity and depends only weakly on the heat flux. This result, as well as the results by Lee and Lee [30], indicates that the dominant mechanism for water micro-channel heat sinks is forced convective boiling but not nucleate boiling.…”

Section: Heat Transfersupporting

confidence: 78%

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Boiling in micro-channels

Hetsroni¹

2010

Bulletin of the Polish Academy of Sciences: Technical Sciences

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Abstract. Boiling heat transfer in micro-channels is a subject of intense academic and practical interest. Though many heat transfer correlations have been proposed, most were empirically formulated from experimental data. However, hydrodynamic and thermal aspects of boiling in micro-channels are not well understood. Moreover, there are only a few theoretical models that link the heat transfer mechanism with flow regimes in micro-channels. Also, there are discrepancies between different sets of published results, and heat transfer coefficients have either well exceeded, or fallen far below, those predicted for conventional channels. Here we consider these problems with regard to micro-channels with hydraulic diameters ranging roughly from 5 µm to 500 µm, to gain a better understanding of the distinct properties of the measurement techniques and uncertainties, the conditions under which the experimental results should be compared to analytical or numerical predictions, boiling phenomenon, as well as different types of micro-channel heat sinks. Two-phase flow maps and heat transfer prediction methods for vaporization in macro-channels are not applicable in micro-channels, because surface tension dominates the phenomena, rather than gravity forces. The models of convection boiling should correlate the frequencies, sizes and velocities of the bubbles and the coalescence processes, which control the flow pattern transitions, together with the heat flux and the mass flux. Therefore, the vapour bubble size distribution must be taken into account. The flow pattern in parallel micro-channels is quite different from that in a single micro-channel. At same values of heat and mass flux, different, time dependent, flow regimes occur in a given micro-channel. At low vapour quality, heat flux causes a sudden release of energy into the vapour bubble, which grows rapidly and occupies the entire channel cross section. The rapid bubble growth pushes the liquid-vapour interface on both caps of the vapour bubble, at the upstream and the downstream ends, and leads to a reverse flow. We term this phenomenon as explosive boiling. One of the limiting operating conditions with flow boiling is the critical heat flux (CHF). The CHF phenomenon is different from that observed in conventional size channels.

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Section: Heat Transfersupporting

confidence: 78%

“…The heat transfer coefficient of boiling flow through a horizontal rectangular channel with low aspect ratio (0.02-0.1) was studied by Lee and Lee [30]. The detail experimental study of flow boiling heat transfer in two-phase heat sinks was performed by Qu and Mudawar [5].…”

Section: Heat Transfermentioning

confidence: 99%

Boiling in micro-channels

Hetsroni¹

2010

Bulletin of the Polish Academy of Sciences: Technical Sciences

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“…At most, a few relevant works seem to be recently published as the references [14][15][16][17][18][19][20]. In an extremely narrow duct, the duct height (not a hydraulic diameter) would be compared to the Laplace constant,…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation of Gas-Liquid Two-Phase Flow in a Horizontally Placed Hydrophobic Rectangular Channel (Part 1, Influence of Abrupt Expansion)

Ueda¹,

Nakajima

Ishii³

et al. 2012

High Temperature Materials and Processes

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This paper aims to computationally investigate flow patterns of gasliquid twophase with an abrupt expansion. To do so, the present computation is nicely verified against the previous experimental results for a good wettability surface. These rectangular channels have a thickness narrower than the Laplace constant of the present situation. Under a poor wettability condition, this narrow thickness affects the flow pattern; e.g., the air phase forms channeling behind the expansion in a low airflow rate whereas the air phase becomes fragments of bubbles due to the expansion under a good wettability condition.

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“…However, even the best predictions showed a mean absolute error (MAE) of 40% against the large experimental database, and predicted less than half of the measured data to within a deviation of ±30%. It was also noted in [1] that most of the existing minichannel and microchannel heat transfer correlations were developed based on small data sets [13][14][15][16][17][18][19][20]. As a result, these correlations usually performed well in the parameter range over which they were fit, but did not extrapolate well beyond their often narrow operating range [1].…”

Section: Introductionmentioning

confidence: 99%

“…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].…”

Section: Introductionmentioning

confidence: 99%