Experimental Study of the Effect of Channel Orientation and Flow Oscillations on Critical Heat Flux

2004 ◽  
Author(s):  
Benjamin Z. Hayes ◽  
Gopinath R. Warrier ◽  
Vijay K. Dhir
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Rectangular Channel ◽  
Oscillation Amplitude ◽  
Saturation Temperature ◽  
Horizontal Flow ◽  
Low Flow ◽  
Cross Sectional ◽  
Average Mass ◽  
Flow Oscillations

Limited studies reported in the literature show that oscillatory flows can reduce critical heat flux (CHF) in boiling channels. In this study the effect of oscillatory flow on the CHF in a rectangular channel is investigated. Oscillation amplitude, average mass flux, and gravity vector orientation were systematically varied in this low-pressure, low-flow study using PF-5060 as the test liquid. The tests were conducted on a test section with a 2 × 2 cm2 cross sectional area and a Hastelloy B-2 ribbon heater mounted flush on one side. The ribbon was 0.406 mm thick and 28.0 cm in length, and was heated using DC power. Oscillations in flow were created by sending a sine wave control signal to a proportional control, solenoid valve. The experiments show that CHF decreases when oscillations are introduced into the flow for vertical upflow (90°) and horizontal flow with the heater surface facing up (0°). CHF values decreased with increasing liquid subcooling, and were nearly insensitive to oscillations at low liquid subcoolings. For horizontal flow, with the heater facing down (180°). CHF was found to be enhanced by the flow oscillations, when the liquid was near saturation temperature.

scholarly journals Orientation Effects on Critical Heat Flux due to Flooding in Thin Rectangular Channel

2002 ◽  
Vol 39 (7) ◽  
pp. 736-742 ◽  
Author(s):  
Futoshi TANAKA ◽  
Kaichiro MISHIMA ◽  
Tamio KOHRIYAMA ◽  
Yukimitsu OKANO
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Rectangular Channel ◽  
Orientation Effects

A study of critical heat flux for low flow of water in vertical round tubes under low pressure

1991 ◽  
Vol 132 (2) ◽  
pp. 225-237 ◽  
Author(s):  
Soon Heung Chang ◽  
Won-Pil Baek ◽  
Tae Min Bae
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Low Pressure ◽  
Low Flow

Subcooled critical heat flux: an assessment of the risk to front-end and beamline components of synchrotron light sources

2010 ◽  
Vol 1 (MEDSI-6) ◽  
Author(s):  
B. Brajuskovic ◽  
D. Capatina ◽  
J. Collins ◽  
P. Den Hartog ◽  
J. Reneker
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Water Saturation ◽  
Saturation Temperature ◽  
Operating Conditions ◽  
Light Sources ◽  
Operational Conditions ◽  
Front End ◽  
Synchrotron Light ◽  
Synchrotron Light Sources

X-ray absorbers in the front ends and beamlines of synchrotron light sources are exposed to very high thermal loads. Many facilities, such as the Advanced Photon Source, are investigating upgrades that will further increase the thermal load. The likelihood of exceeding the limit of subcooled critical heat flux (CHF) in these components was examined. The assessment was performed for both currently possible off-normal operational conditions, such as might occur in the event of a failure of multiple safety interlocks, and the anticipated operating conditions that may result from future upgrades. The subcooled CHF values were calculated using empirical equations frequently cited in the literature and then compared with the computed values of the heat flux at the walls of the component cooling channels in cases where the cooling wall temperature exceeded the water saturation temperature at local hydraulic conditions. Having in mind that the great majority of the available empirical correlations were developed for the conditions characteristic for the operation of heat exchangers in the nuclear power industry, the limitations of this approach are discussed and an experimental study of the subcooled CHF values in the conditions similar to those expected in the front-end and beamline components is proposed.

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.

Effect of Cross-Sectional Perturbation on Critical Heat Flux Criteria in Microchannels

2013 ◽  
Vol 135 (10) ◽  
Author(s):  
Mark J. Miner ◽  
Patrick E. Phelan
Keyword(s):  
Experimental Data ◽  
Heat Flux ◽  
Phase Velocity ◽  
Critical Heat Flux ◽  
Flow Boiling ◽  
Channel Diameter ◽  
Cross Sectional ◽  
Growing Body ◽  
Circular Microchannel ◽  
Expanding Channel

A variety of predictive correlations for critical heat flux (CHF) are examined in light of the growing body of work exploring enhanced flow boiling CHF via cross-sectional expansion. The analysis considers the effect of a small perturbation of the diameter of a circular microchannel on the predictions made by the selected criteria, and seeks to demonstrate an optimum rate of expansion. It is demonstrated that a nonzero diameter expansion necessarily improves performance under several criteria for critical heat flux, and an optimum expansion rate exists for many of these criteria. CHF relations are seen to follow a few distinct types, and those relations which contemplate effects which may directly influence CHF, such as pressure and phase velocity, tend to better reflect the experimentally demonstrated effect of the expanding channel diameter on CHF. Experimental data are examined from several investigators, including the authors' group, and the validity of both the criteria and the analysis is compared to the data.

Critical Heat Fluxes and Flow Patterns in High-Pressure Boiling Water Flows

1964 ◽  
Vol 86 (1) ◽  
pp. 12-22 ◽  
Author(s):  
F. E. Tippets
Keyword(s):  
Heat Flux ◽  
High Pressure ◽  
Critical Heat Flux ◽  
Rectangular Channel ◽  
Motion Pictures ◽  
Flow Patterns ◽  
Heat Fluxes ◽  
Boiling Water ◽  
Forced Flow ◽  
Flux Level

High-speed motion pictures (4300 pictures/sec) of boiling water flow patterns in conditions of forced flow at 1000 psia pressure in a vertical heated rectangular channel were taken over the range of mass velocities from 50 to 400 lb/sec-ft2, fluid states from bulk subcooled liquid flow to bulk boiling flow at 0.66 steam quality, and heat fluxes up to and including the critical heat flux level. Eighty critical heat flux determinations were made in the course of the experiment at 1000 psia in conditions of bulk boiling. The motion pictures provide photographic evidence of the general arrangement of the flow in conditions of bulk boiling at high pressure with heat fluxes near and including the critical heat flux level.

scholarly journals EXPERIMENTAL INVESTIGATION OF CRITICAL HEAT FLUX IN ANNULUS AT LOW PRESSURE AND LOW FLOW PARAMETERS

2020 ◽  
Vol 28 ◽  
pp. 50-58
Author(s):  
Daniel Vlček ◽  
Ladislav Suk ◽  
Kamil Števanka ◽  
Taron Petrosyan
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Flow Boiling ◽  
Low Pressure ◽  
Low Flow ◽  
Inconel 625 ◽  
Outer Diameter ◽  
Flow Parameters ◽  
Low Mass ◽  
Vertically Aligned

Steady state flow boiling experiments were conducted on a technically smooth Inconel 625 tube with outer diameter 9.1 mm at inlet pressures 131, 220 and 323 kPa, inlet temperatures 62, 78 and 94 °C and approximately 400, 600 and 1000 kg/(m2.s) mass flow. Water of these parameters was entering into the vertically aligned annulus, where the uniformly heated tube was placed until the critical heat flux (CHF) appeared. The experimental data were compared to estimations of CHF by local PGT tube correlation and Groeneveld’s look-up tables for tubes. The results imply that in the region of low pressure and low mass flux, the differences between calculations and experiments are substantial (more than 50 % of CHF). The calculations further imply that look-up tables and tube correlations should be corrected to the annulus geometry. Here, the Doerffer’s approach was chosen and led to a substantial enhancement of CHF estimation. Yet, a new correlation for the region of low pressure and flow is needed.

An Experimental Study on the Critical Heat Flux for Low Flow of Water in Bilaterally Heated Vertical Annuli Under Low Pressure Conditions

2014 ◽  
Author(s):  
Lei Zhou ◽  
Guangxu Liu ◽  
Yuanfeng Zan ◽  
Xiao Yan
Keyword(s):  
Experimental Study ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Nuclear Power ◽  
Low Pressure ◽  
Operating Conditions ◽  
Low Flow ◽  
Plant Design ◽  
Water Reactors ◽  
Vertical Annuli

Critical heat flux (CHF) has been widely studied in the past decades because of its importance for nuclear power plant design. But most of the studies are based on flow under normal operating conditions for light water reactors. CHF under low flow and low pressure is of significance when considering operating transients and accidents. In this study, experimental study has been carried out on CHF for low flow rate and low pressure water flow in vertical bilaterally heated annuli. Parameter trends on CHF is discussed and a new predictive correlation was fitted based on the CHF data points. This study is meaningful for concerned nuclear engineering and similar experiment design.

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