Prediction of Critical Heat Flux for Saturated Flow Boiling Water in Vertical Narrow Rectangular Channels

An experimental facility is developed to investigate critical heat flux (CHF) of saturated flow boiling of Refrigerant-123 (R-123) in microchannels. Six parallel Microchannels with cross sectional area of 0.2 mm × 0.2 mm are fabricated on a copper block, and a Polyvinyl Chloride (PVC) cover is then placed on top of the copper block to serve as a transparent cover through which flow patterns and boiling phenomena could be observed. A resistive cartridge heater is used to provide a uniform heat flux to the microchannels. The experimental test facility is designed to accommodate test sections with different microchannel geometries. The mass flow rate, inlet pressure, inlet temperature of Refrigerant-123, and the electric current supplied to the resistive cartridge heater are controlled to provide quantitative information near the CHF condition in microchannels. A high-speed camera is used to observe and interpret flow characteristics of CHF condition in microchannels.

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Experimental Investigation of Critical Heat Flux and Boiling-Bubble Behavior in Saturated Flow Boiling under Vibration Condition

The Proceedings of the National Symposium on Power and Energy Systems ◽

10.1299/jsmepes.2016.21.a233 ◽

2016 ◽

Vol 2016.21 (0) ◽

pp. A233

Author(s):

Tomonobu Nara ◽

Hiroyasu Ohtake ◽

Koji Hasegawa ◽

Junpei Ogawa

Keyword(s):

Heat Flux ◽

Experimental Investigation ◽

Critical Heat Flux ◽

Flow Boiling ◽

Bubble Behavior ◽

Saturated Flow ◽

Vibration Condition

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Correlation for Flow Boiling Critical Heat Flux in Thin Rectangular Channels

Journal of Heat Transfer ◽

10.1115/1.3216037 ◽

2009 ◽

Vol 131 (12) ◽

Cited By ~ 14

Author(s):

Futoshi Tanaka ◽

Takashi Hibiki ◽

Kaichiro Mishima

Keyword(s):

Heat Flux ◽

Critical Heat Flux ◽

Flow Boiling ◽

Rectangular Channels ◽

Hydraulic Design ◽

Wide Range ◽

Outlet Flow ◽

Triggering Mechanisms ◽

Small Channels ◽

Heated Length

The effect of heated length on critical heat flux (CHF) in thin rectangular channels under atmospheric pressure has been studied. CHF in small channels has been widely studied in the last decades but most of the studies are based on flow in round tubes and number of studies focused on rectangular channels is relatively small. Although basic triggering mechanisms, which lead to CHF in thin rectangular channels, are similar to that of tubes, applicability of thermal hydraulic correlations developed for tubes to rectangular channels are questionable since heat transfer in rectangular channels are affected by the existence of nonheated walls and the noncircular geometry of channel circumference. Several studies of CHF in thin rectangular channels have been reported in relation to thermal hydraulic design of research reactors and neutron source targets and correlations have been proposed, but the studies mostly focus on geometrical conditions of the application of interest and therefore effect of channel parameters exceeding their interest is not fully understood. In his study, CHF data for thin rectangular channels have been collected from previous studies and the effect of heated length on CHF was examined. Existing correlations were verified with data with positive quality outlet flow but none of the correlations successfully reproduced the data for a wide range of heated lengths. A new CHF correlation for quality region applicable to a wide range of heated lengths has been developed based on the collected data.

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