A theoretical and experimental study on subcooled flow boiling at high heat flux

Subcooled flow boiling of water has been investigated for the horizontal multi-microchannel of which hydraulic diameter is 150μm for unit channel. Eleven rectangular microchannels are made on a top of copper heating block of 5.25mm × 5.25mm. The outlet of the channel is opened to the atmospheric surroundings and the maximum pressure in the channel is lower than 25mmHg. The boiling test is performed under the nearly atmospheric condition. The experimental results are discussed compared with subcooled boiling of water in a microchannel of 155μm in hydraulic diameter with Platinum film microheater of 2000μm in length and 200μm in width obtained by Ping Cheng and his co-workers. According to the authors’ previous experiments on subcooled flow boiling in mini and conventional channels, the critical heat flux decreases with decreasing of the hydraulic diameter of the channel. The boiling in the microchannel turns to film boiling after reaching CHF without microbubble emission boiling (MEB) regardless of liquid subcooling and liquid velocity even if the boiling condition is the same as MEB in the minichannels. In the high heat flux region, whole of the microchannels is completely covered with large coalescing bubbles. The results are much different from those of experiments with Platinum film microheater, which have 14.41 MW/m2 of heat flux in MEB. It is difficult to introduce liquid–vapor exchange including MEB for the large capacitance heat sink in microchannel boiling.

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A Photographic study of subcooled flow boiling burnout at high heat flux and velocity

International Journal of Heat and Mass Transfer ◽

10.1016/j.ijheatmasstransfer.2006.06.020 ◽

2007 ◽

Vol 50 (1-2) ◽

pp. 283-291 ◽

Cited By ~ 8

Author(s):

G.P. Celata ◽

M. Cumo ◽

D. Gallo ◽

A. Mariani ◽

G. Zummo

Keyword(s):

Heat Flux ◽

Flow Boiling ◽

High Heat ◽

High Heat Flux ◽

Subcooled Flow Boiling ◽

Subcooled Flow

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Single-Side Heated Monoblock, High Heat Flux Removal Using Water Subcooled Flow Boiling

Heat Transfer: Volume 2 ◽

10.1115/ht2003-47422 ◽

2003 ◽

Author(s):

Ronald D. Boyd ◽

Ali Ekhlassi ◽

Penrose Cofie ◽

Richard Martin ◽

Hongtao Zhang

Keyword(s):

Heat Flux ◽

Wall Temperature ◽

Test Section ◽

Flow Boiling ◽

Three Dimensional ◽

High Heat ◽

High Heat Flux ◽

Subcooled Flow Boiling ◽

Subcooled Flow ◽

Single Side

Plasma-facing components for fusion reactors and other high heat flux heat sinks are usually subjected to a peripherally non-uniform heat flux. The configuration under study is related to these applications and consists of a single-side heated monoblock cross-section test section with a circular coolant channel bored through the center. The monoblock test section has a heated length of 180.0 mm and has 10.0 mm and 30.0 mm inside diameter and outside square sides, respectively. It was subjected to a constant heat flux on one side only, and the remaining portion of the outside surfaces is not exposed to a heat flux. The inlet channel water temperature was held near at 26.0°C, the exit pressure was maintained at 0.207 MPa, and the mass velocity was 0.59 Mg/m2s. The results consist of three-dimensional monoblock test section wall temperature distributions and a clear display of both critical heat flux and post-critical heat flux for this single-side heated configuration. These results are very encouraging in that they are among the first full set of truly three-dimensional monoblock test section wall temperature measurements for a one-side heated monoblock flow channel which contains the effects of conjugate heat transfer for turbulent, subcooled flow boiling. Comparisons are made between these results for the monoblock test section and those for a single-side heated circular test section.

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