Post-dryout heat transfer to high-pressure water flowing upward in vertical channels with various flow obstacles

Anghel, Ionut Gheorghe; Anglart, Henryk

doi:10.1016/j.ijheatmasstransfer.2012.08.036

Cited by 13 publications

(2 citation statements)

References 27 publications

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“…The focus of this work is to apply NT on circular vertical pipe test sections, which is a common geometry for two-phase flow experiments, implemented, for example, at the HWAT test loop in Stockholm, 16 Sweden. In this case, the axial symmetry of the investigated object makes one of the pivot points obsolete, since any rotation around the center of the circular test section results would result in an equivalent measurement.…”

Section: Tomography On Axially Symmetric Objectsmentioning

confidence: 99%

Neutron tomography of axially symmetric objects using 14 MeV neutrons from a portable neutron generator

Andersson

Andersson-Sundén

Sjöstrand

et al. 2014

Review of Scientific Instruments

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In nuclear boiling water reactor cores, the distribution of water and steam (void) is essential for both safety and efficiency reasons. In order to enhance predictive capabilities, void distribution assessment is performed in two-phase test-loops under reactor-relevant conditions. This article proposes the novel technique of fast-neutron tomography using a portable deuterium-tritium neutron generator to determine the time-averaged void distribution in these loops. Fast neutrons have the advantage of high transmission through the metallic structures and pipes typically concealing a thermal-hydraulic test loop, while still being fairly sensitive to the water/void content. However, commercially available fast-neutron generators also have the disadvantage of a relatively low yield and fast-neutron detection also suffers from relatively low detection efficiency. Fortunately, some loops are axially symmetric, a property which can be exploited to reduce the amount of data needed for tomographic measurement, thus limiting the interrogation time needed. In this article, three axially symmetric test objects depicting a thermal-hydraulic test loop have been examined; steel pipes with outer diameter 24 mm, thickness 1.5 mm, and with three different distributions of the plastic material POM inside the pipes. Data recorded with the FANTOM fast-neutron tomography instrument have been used to perform tomographic reconstructions to assess their radial material distribution. Here, a dedicated tomographic algorithm that exploits the symmetry of these objects has been applied, which is described in the paper. Results are demonstrated in 20 rixel (radial pixel) reconstructions of the interior constitution and 2D visualization of the pipe interior is demonstrated. The local POM attenuation coefficients in the rixels were measured with errors (RMS) of 0.025, 0.020, and 0.022 cm(-1), solid POM attenuation coefficient. The accuracy and precision is high enough to provide a useful indication on the flow mode, and a visualization of the radial material distribution can be obtained. A benefit of this system is its potential to be mounted at any axial height of a two-phase test section without requirements for pre-fabricated entrances or windows. This could mean a significant increase in flexibility of the void distribution assessment capability at many existing two-phase test loops.

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Section: Tomography On Axially Symmetric Objectsmentioning

confidence: 99%

Neutron tomography of axially symmetric objects using 14 MeV neutrons from a portable neutron generator

Andersson

Andersson-Sundén

Sjöstrand

et al. 2014

Review of Scientific Instruments

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“…In the design of CFB boiler in Shanghai Boiler Factory, the evaporation heating surface arranged downward is used. At present, many studies investigate the heat transfer characteristics of the watercooled wing-wall, [7][8][9][10][11][12][13][14][15][16][17] including the influence of different heating methods, mass flow, and pressure on heat transfer. However, the ultrasupercritical CFB boiler has a large working pressure span and a complicated operation mode necessary to prevent the deterioration of heat transfer and deformation of the heating element due to the maldistribution of the working fluid and then affect the safe operation of the boiler.…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation on gas‐liquid flow distribution in downward parallel pipes of a 660 MW ultrasupercritical CFB boiler

Xin

Niu

et al. 2020

Intl J of Energy Research

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The arrangement of downward flowing evaporation heating surface in the furnace can effectively reduce the height of the furnace in the ultrasupercritical circulating fluidized bed boiler. According to the structural parameters of 660 MW ultrasupercritical circulating fluidized bed boiler, the scaled experimental system was established on the basis of the similarity criterion. The distribution of the gas-liquid two-phase flow in the parallel branch pipes of the downward and the upward water-cooled wing-wall was studied under the rated loads of 25%, 50%, and 70% THA. The void fraction distribution, flow distribution of each phase, and dryness distribution in each branch pipe of the downcomers and the risers of the water-cooled wing-wall were measured via the quick-closing valve method and the split-phase measurement method. In the downward water-cooled wingwall, both the nonuniform coefficient of void fraction and dryness in each branch pipe decreased with the increase in dryness in the inlet header. Under the same average dryness, the nonuniform coefficient of the void fraction increased with the increase in load. In the upward water-cooled wing-wall, under the same load, the uniformity of flow distribution was improved as the dryness increases. Under the same dryness condition, as the boiler load increases, the deviation coefficient of each phase distribution between the parallel pipes increased and the unevenness increased. In the study of flow and heat transfer characteristics of two-phase flow, the void fraction α is a very important intermediate calculation parameter. The correlation formula of the cross-sectional void fraction in the downward water-cooled wing-wall was fitted, and the calculation result was better compared with drift-flux model, with an error of −6% to 6%.

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Experimental investigation on heat transfer characteristics of smooth tube with downward flow

Shen

Yang

Chen

et al. 2014

International Journal of Heat and Mass Transfer

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Post-dryout heat transfer to high-pressure water flowing upward in vertical channels with various flow obstacles

Cited by 13 publications

References 27 publications

Neutron tomography of axially symmetric objects using 14 MeV neutrons from a portable neutron generator

Neutron tomography of axially symmetric objects using 14 MeV neutrons from a portable neutron generator

Experimental investigation on gas‐liquid flow distribution in downward parallel pipes of a 660 MW ultrasupercritical CFB boiler

Experimental investigation on heat transfer characteristics of smooth tube with downward flow

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