Study on Saturated Flow Boiling Heat Transfer Under Vibration Conditions

2012 ◽  
Author(s):  
Yoshitaro Fujiyama ◽  
Hiroyasu Ohtake
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Test Section ◽  
Low Voltage ◽  
Flow Boiling ◽  
Heating Surface ◽  
Nucleate Boiling ◽  
Circuit Board ◽  
Vertical Position ◽  
Saturated Flow

The ability to predict void formation, void fraction and critical heat flux —CHF— in flow boiling under oscillatory flow and vibration conditions is important to the safety technology of nuclear reactor during earthquake. In the present study, the onset of nucleate boiling —ONB— and CHF on saturated flow boiling under vibration conditions were investigated experimentally. Steady state experiments were conducted using a copper thin-film and saturated and subcooled water at 0.1 MPa. The liquid velocity was 0.25, 1.38, 3.20 and 4.07 m/s, respectively; the liquid subcooling was 0 K and 20 K. A heater was made of a printed circuit board. A test section was a rectangular flow channel of 10 mm width and 10 mm height. The test heater was heated by Joule heating of d.c. current from a low-voltage high-current stabilizer. The heating rate of the heater was determined from supplied current and voltage. The temperature of the heater was obtained by referring to the measured electric resistance. The test section was arranged for horizontal position facing upward and for vertical position, respectively. For the vibration condition, the test section was set on a vibration table. The ONB was decided as an occurrence of the first boiling bubble. The critical heat flux was determined as that immediately before the heating surface physically burned-out. The CHF on saturated flow boiling under vibration conditions were investigated experimentally.

Study on Subcooled-Forced Flow Boiling Heat Transfer and Critical Heat Flux of Solid-Water Two-Phase Mixture

1999 ◽  
Author(s):  
Yasuo Koizumi ◽  
Hiroyasu Ohtake ◽  
Manabu Mochizuki
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Liquid Layer ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
Forced Flow ◽  
Superheated Liquid ◽  
Flow Boiling Heat Transfer

Abstract The effect of solid particle introduction on subcooled-forced flow boiling heat transfer and a critical heat flux was examined experimentally. In the experiment, glass beads of 0.6 mm diameter were mixed in subcooled water. Experiments were conducted in a range of the subcooling of 40 K, a velocity of 0.17–6.7 m/s, a volumetric particle ratio of 0–17%. When particles were introduced, the growth of a superheated liquid layer near a heat trasnsfer surface seemed to be suppressed and the onset of nucleate boiling was delayed. The particles promoted the condensation of bubbles on the heat transfer surface, which shifted the initiation of a net vapor generation to a high heat flux region. Boiling heat trasnfer was augmented by the particle introduction. The suppression of the growth of the superheated liquid layer and the promotion of bubble condensation and dissipation by the particles seemed to contribute that heat transfer augmentation. The wall superheat at the critical heat flux was elevated by the particle introduction and the critical heat flux itself was also enhanced. However, the degree of the critical heat flux improvement was not drastic.

Development of an Experimental Facility for Investigating Critical Heat Flux of Saturated Flow Boiling of Refrigerant-123 in Microchannels

2005 ◽  
Author(s):  
Wai Keat Kuan ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Flow Boiling ◽  
Test Facility ◽  
Uniform Heat Flux ◽  
Inlet Temperature ◽  
Experimental Facility ◽  
Copper Block ◽  
Saturated Flow ◽  
Cartridge Heater

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.

Two-Phase Pipe Quenching Correlations for Liquid Nitrogen and Liquid Hydrogen

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
S. R. Darr ◽  
J. W. Hartwig ◽  
J. Dong ◽  
H. Wang ◽  
A. K. Majumdar ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Liquid Nitrogen ◽  
Critical Heat Flux ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
Liquid Hydrogen ◽  
Two Phase ◽  
Cryogenic Flow ◽  
Two Phase Heat Transfer

Recently, two-phase cryogenic flow boiling data in liquid nitrogen (LN2) and liquid hydrogen (LH2) were compared to the most popular two-phase correlations, as well as correlations used in two of the most widely used commercially available thermal/fluid design codes in Hartwig et al. (2016, “Assessment of Existing Two Phase Heat Transfer Coefficient and Critical Heat Flux on Cryogenic Flow Boiling Quenching Experiments,” Int. J. Heat Mass Transfer, 93, pp. 441–463). Results uncovered that the correlations performed poorly, with predictions significantly higher than the data. Disparity is primarily due to the fact that most two-phase correlations are based on room temperature fluids, and for the heating configuration, not the quenching configuration. The penalty for such poor predictive tools is higher margin, safety factor, and cost. Before control algorithms for cryogenic transfer systems can be implemented, it is first required to develop a set of low-error, fundamental two-phase heat transfer correlations that match available cryogenic data. This paper presents the background for developing a new set of quenching/chilldown correlations for cryogenic pipe flow on thin, shorter lines, including the results of an exhaustive literature review of 61 sources. New correlations are presented which are based on the consolidated database of 79,915 quenching points for a 1.27 cm diameter line, covering a wide range of inlet subcooling, mass flux, pressure, equilibrium quality, flow direction, and even gravity level. Functional forms are presented for LN2 and LH2 chilldown correlations, including film, transition, and nucleate boiling, critical heat flux, and the Leidenfrost point.

Experimental Study of Flow Critical Heat Flux in Low Concentration Water-Based Nanofluids

2008 ◽  
Author(s):  
Sung Joong Kim ◽  
Tom McKrell ◽  
Jacopo Buongiorno ◽  
Lin-Wen Hu
Keyword(s):  
Experimental Study ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Test Section ◽  
Flow Boiling ◽  
Saturation Temperature ◽  
Outlet Temperature ◽  
Flow Loop ◽  
Maximum Heat ◽  
Low Concentration

Nanofluids are known as dispersions of nano-scale particles in solvents. Recent reviews of pool boiling experiments using nanofluids have shown that they have greatly enhanced critical heat flux (CHF). In many practical heat transfer applications, however, it is flow boiling that is of particular importance. Therefore, an experimental study was performed to verify whether or not a nanofluid can indeed enhance the CHF in the flow boiling condition. The nanofluid used in this work was a dispersion of aluminum oxide particles in water at very low concentration (≤0.1 v%). CHF was measured in a flow loop with a stainless steel grade 316 tubular test section of 5.54 mm inner diameter and 100 mm long. The test section was designed to provide a maximum heat flux of about 9.0 MW/m2, delivered by two direct current power supplies connected in parallel. More than 40 tests were conducted at three different mass fluxes of 1,500, 2,000, and 2,500 kg/m2sec while the fluid outlet temperature was limited not to exceed the saturation temperature at 0.1 MPa. The experimental results show that the CHF could be enhanced by as much as 45%. Additionally, surface inspection using Scanning Electron Microscopy reveals that the surface morphology of the test heater has been altered during the nanofluid boiling, which, in turn, provides valuable clues for explaining the CHF enhancement.

Critical heat flux enhancement on a downward face using porous honeycomb plate in saturated flow boiling

2017 ◽  
Vol 109 ◽  
pp. 454-461 ◽  
Author(s):  
Laishun Wang ◽  
Abdul R. Khan ◽  
Nejdet Erkan ◽  
Haiguang Gong ◽  
Koji Okamoto
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Flow Boiling ◽  
Saturated Flow ◽  
Flux Enhancement

Nucleate Boiling and Critical Heat Flux From Protruded Chip Arrays During Flow Boiling

1993 ◽  
Vol 115 (1) ◽  
pp. 78-88 ◽  
Author(s):  
C. O. Gersey ◽  
I. Mudawar
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Single Phase ◽  
Liquid Velocity ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Subcooled Flow

The effects of chip protrusion on the forced-convection boiling and critical heat flux (CHF) of a dielectric coolant (FC-72) were investigated. The multi-chip module used in the present study featured a linear array of nine, 10 mm x 10 mm, simulated microelectronic chips which protruded 1 mm into a 20-mm wide side of a rectangular flow channel. Experiments were performed in vertical up flow with 5-mm and 2-mm channel gap thicknesses. For each configuration, the velocity and subcooling of the liquid were varied from 13 to 400 cm/s and 3 to 36° C, respectively. The nucleate boiling regime was not affected by changes in velocity and subcooling, and critical heat flux generally increased with increases in either velocity or subcooling. Higher single-phase heat transfer coefficients and higher CHF values were measured for the protruded chips compared to similar flush-mounted chips. However, adjusting the data for the increased surface area and the increased liquid velocity above the chip caused by the protruding chips yielded a closer agreement between the protruded and flush-mounted results. Even with the velocity and area adjustments, the most upstream protruded chip had higher single-phase heat transfer coefficients and CHF values for high velocity and/or highly-subcooled flow as compared the downstream protruded chips. The results show that, except for the most upstream chip, the performances of protruded chips are very similar to those of flush-mounted chips.

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