VAPOR GENERATION RATE IN NONEQUILIBRIUM CONVECTIVE FILM BOILING

Axially Varying Vapor Superheats in Convective Film Boiling

Journal of Heat Transfer ◽

10.1115/1.3247475 ◽

1985 ◽

Vol 107 (3) ◽

pp. 663-669 ◽

Cited By ~ 14

Author(s):

D. Evans ◽

S. W. Webb ◽

J. C. Chen

Keyword(s):

Steady State ◽

Vertical Tube ◽

Heat Fluxes ◽

Generation Rate ◽

Film Boiling ◽

Vapor Generation ◽

Mass Flow Rates ◽

Time Required ◽

Process Measurements ◽

Vapor Temperature

Axially varying vapor superheats in convective film boiling have been measured for water flowing in a vertical tube at low to moderate pressures and mass flow rates. Using a slow “reflood” process, measurements of wall temperature and nonequilibrium vapor temperature were obtained as functions of distance from the quench front. With the low quench front velocity, the time required to progapate the front a few millimeters corresponds to many fluid residence times, and the thermal hydraulic data thus obtained are quasi-steady state. These experimental results indicate a zone near the quench front where the vapor generation rate is relatively high, followed by a far zone where the generation rate drops off to a relatively low magnitude. The data obtained agree with the very limited previously reported steady-state data. Comparison with existing heat transfer models shows the models give poor predictions of vapor superheats but reasonable predictions of wall heat fluxes.

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Vapor generation rate model for dispersed drop flow

Nuclear Engineering and Design ◽

10.1016/0029-5493(91)90075-s ◽

1991 ◽

Vol 125 (2) ◽

pp. 161-173 ◽

Cited By ~ 7

Author(s):

Cetin Unal ◽

Kemal Tuzla ◽

Asuman F. Cokmez-Tuzla ◽

John C. Chen

Keyword(s):

Generation Rate ◽

Rate Model ◽

Vapor Generation ◽

Drop Flow

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Experimental investigation on pool boiling for downward facing heating with different concentrations of Al2O3 nanofluids

Kerntechnik ◽

10.1515/kern-2020-0090 ◽

2021 ◽

Vol 86 (2) ◽

pp. 96-105

Author(s):

Z. Zhou ◽

Y. Gao ◽

H.-E. Hsieh ◽

H. Miao ◽

Z. Zhang

Keyword(s):

Heat Transfer ◽

Boiling Heat Transfer ◽

Early Stage ◽

Surface Heat ◽

Generation Rate ◽

Film Boiling ◽

Vapor Film ◽

Bubble Generation ◽

Two Factors ◽

The Heat Transfer Coefficient

Abstract An experimental study has been conducted to examine the effect of different concentrations of α-Al2O3 nanofluids on boiling heat transfer for downward facing heating. The experimental results indicated that the surface heat transfer was enhanced with the rise of the nanofluids concentration, due to the bubble generation rate and disturbance increased. For downward facing heating, bubbles were not able to escape since the bouncy force influenced, and the vapor film appeared earlier as the increase of bubble generation rate. However, the heat transfer coefficient remains at a relatively high value in the early stage of film boiling, which suppresses the deterioration of heat transfer, due to the influences of nanofluids. As the various concentrations of nanofluids increased from 0 g/L to 0.012 g/L, it was found that the enhancement of the CHF (critical heat flux) up to 20.5%. After the nanofluids boiling, the surface roughness decreased and the wettability became worse. From the experimental phenomena, under the influence of these two factors, the bubble activity was enhanced.

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