Effects of heater surface orientation on the critical heat flux—II. A model for pool and forced convection subcooled boiling

Heat removal through pool boiling is limited by the phenomena of critical heat flux (CHF). CHF enhancement is vitally important in order to satisfy demand for the cooling technology with high heat flux in In Vessel Retention (IVR). Various surface modifications of the boiling surface, e.g., integrated surface structures and coating of a micro-porous have been proven to effectively enhance the CHF in saturated pool boiling. We have been proposed a novel method of attaching a honeycomb structured porous plate on a considerably large heater surface. Previous results, by the authors in [1] reported that CHF has been enhanced experimentally up to more than approximately twice that of a plain surface (approximately 2.0 to 2.5 MW/m2) with a diameter of 30 mm heated surface. However, it is necessary to demonstrate the method together with infinite heater surface within laboratory scale. It is important that cooling techniques for IVR could be applicable to a large heated surface as well as remove high heat flux. Objective of this study is to investigate the CHF of honeycomb porous plate and metal solid structure in nanofluid boiling or water boiling on a large heated surface. Water-based nanofluid offers good wettability and capillarity. While metal solid structure is installed on honeycomb porous plate to increase the number of vapor jet. Experimental results of honeycomb porous plate and combination of honeycomb porous plate and metal solid structure in water-based nanofluid boiling shows that CHF is increased up to twice [2] and thrice, respectively compared to plain surface in water boiling. To the best of the author’s knowledge, the highest value (3.1 MW/m2) was obtained for a large heated surface having a diameter of 50 mm which is regarded as infinite heated surface. This demonstrates potential for general applicability to have more safety margin in IVR method.

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Critical Heat Flux in Forced Convective Subcooled Boiling With Multiple Impinging Jets

Journal of Heat Transfer ◽

10.1115/1.2824051 ◽

1996 ◽

Vol 118 (1) ◽

pp. 241-243 ◽

Cited By ~ 22

Author(s):

M. Monde ◽

Y. Mitsutake

Keyword(s):

Heat Flux ◽

Critical Heat Flux ◽

Impinging Jets ◽

Subcooled Boiling

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Subcooled Boiling Heat Transfer for Turbulent Flow of Water in a Short Vertical Tube

Journal of Heat Transfer ◽

10.1115/1.3194768 ◽

2009 ◽

Vol 132 (1) ◽

Cited By ~ 20

Author(s):

Koichi Hata ◽

Suguru Masuzaki

Keyword(s):

Heat Transfer ◽

Heat Flux ◽

Turbulent Flow ◽

Critical Heat Flux ◽

Boiling Heat Transfer ◽

Vertical Tube ◽

Test Tube ◽

Subcooled Boiling ◽

Transfer Coefficients ◽

Infrared Thermal Imaging

The subcooled boiling heat transfer and the critical heat flux (CHF) due to exponentially increasing heat inputs with various periods (Q=Q0 exp(t/τ), τ=22.52 ms–26.31 s) were systematically measured by an experimental water loop flow and observed by an infrared thermal imaging camera. Measurements were made on a 3 mm inner diameter, a 66.5 mm heated length, and a 0.5 mm thickness of platinum test tube, which was divided into three sections (upper, mid, and lower positions). The axial variations of the inner surface temperature, the heat flux, and the heat transfer coefficient from nonboiling to critical heat flux were clarified. The results were compared with other correlations for the subcooled boiling heat transfer and authors’ transient CHF correlations. The influence of exponential period (τ) and flow velocity on the subcooled boiling heat transfer and the CHF was investigated and the predictable correlation of the subcooled boiling heat transfer for turbulent flow of water in a short vertical tube was derived based on the experimental data. In this work, the correlation gave 15% difference for subcooled boiling heat transfer coefficients. Most of the CHF data (101 points) were within 15% and −30 to +20% differences of the authors’ transient CHF correlations against inlet and outlet subcoolings, respectively.

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