Heat transfer distribution and pressure fluctuations during flow boiling in a pipe with different orientations

Kumar, Arvind; Hardik, B.K.

doi:10.1016/j.applthermaleng.2021.117822

Cited by 11 publications

(3 citation statements)

References 33 publications

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“…LL工质间的相互作用 [36] 减弱, f仅受惯性力影响, 15 MPa以后水平管阻力压降不再受压力影响. 综上所述, 超临界流体阻力压降的变化趋势与亚临界两相流的阻力压降比单相流大的规律 [37] 相似.…”

Section: 垂直向上管中 Sbo数是区分正常传热和传unclassified

Effect of flow direction on heat transfer and flow characteristics of supercritical carbon dioxide

Cheng,

2024

Acta Phys. Sin.

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The paper is devoted to investigate the difference of flow and heat transfer characteristics between vertical upward and horizontal flow of supercritical carbon dioxide (sCO2) based on the pseudo-boiling theory, covering a range of experimental parameters: mass flux G=496~1100 kg/m2s; heat flux qw=54.4~300.2 kW/m2; pressure P=7.531~20.513 MPa. The distinctions of flow and heat transfer characteristics between horizontal and vertical upward tubes are compared at different mass flux, heat flux and pressure fully. Finally, Different from the classical treatment of flow and heat transfer for supercritical fluid, single-phase fluid assumption is abandoned, Instead, the pseudo-boiling theory is introduced to deal with the flow and heat transfer of sCO2 in two tubes. Supercritical fluid is regarded as a multiphase structure in this paper, including a vapor-like layer near the wall and a liquid-like fluid in tube core. The results indicate that: 1) In terms of heat transfer, the inner-wall temperature of the vertical upward tube and the bottom generatrix of horizontal tube are basically the same under normal heat transfer mode. When heat transfer deterioration occurs in the vertical upward tube, larger supercritical boiling number SBO will cause the wall temperature peak of the vertical upward tube to be much higher than the wall temperature at top generatrix of the horizontal tube at the corresponding enthalpy. The SBO (SBO=5.126×10-4) distinguishes between normal heat transfer and heat transfer deterioration in the vertical upward tube. In horizontal tubes, SBO dominates the maximum wall temperature difference between the top and bottom generatrix. Compared with vertical upward tubes, higher qw/G is required for heat transfer deterioration of supercritical fluid in horizontal tubes under the same pressure. 2) In terms of flow: The increase in slope of pressure drop in vertical upward tubes is due to the orifice contraction effect. The mechanism that dominates the variation of pressure drop in horizontal tubes is the flow stratification effect, and we show that Froude number Frave can be the similarity criterion number to connect the temperature difference between the top and bottom generatrix of horizontal tubes and the pressure drop. The analysis suggests that mechanisms governing horizontal and vertical flows of sCO2 are different in heat transfer deterioration mode. For the vertical flow, the SBO plays a leading role, while for the horizontal flow, the Fr plays an indispensable role.

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Section: 垂直向上管中 Sbo数是区分正常传热和传unclassified

Effect of flow direction on heat transfer and flow characteristics of supercritical carbon dioxide

Cheng,

2024

Acta Phys. Sin.

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“…The heat input is measured by multiplying the supplied current (I) and voltage (V). The heat transfer coefficient (h) is calculated using the eq (1). The inlet and exit vapor quality (x) at z=0 and z=L, respectively, are calculated using eq (2).…”

Section: Data Reductionmentioning

confidence: 99%

“…Flow boiling is used significantly in petrochemical, power plants, chemical plants, steam generators, high-temperature recuperators, synthetic natural gas industries, stator cooling, nuclear plants, and process industries [1]. Flow boiling is preferred due to its advantage of massive heat transfer of the sensible and latent heat compared to single phase heat transfer.…”

Section: Introductionmentioning

confidence: 99%

Heat Transfer And Wall Temperature Distribution During Flow Boiling In Conventional And Mini Channels

Kumar,

Kothadia

2023

Proceedings of the 9th World Congress on Mechanical, Chemical, and Material Engineering

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The fluctuation of pressure in flow boiling is affected due to liquid-vapor phase interaction, and thus the flow and wall temperature are influenced. The temporal and spatial variation of wall temperature and the heat transfer coefficient are investigated experimentally at atmospheric system pressure. The two mini-tubes of 2×300 and 4×600 mm inner diameter× heated length are used for analysis. The thermal image technology is used to show the wall temperature distribution. The experimental setup is validated by comparing the heat transfer coefficient with Dittus-Boelter and Gnielinski correlations. The boiling heat transfer coefficient in both tubes are compared to get the effect of diameter, mass flux and heat flux. The radially as well as axially variation of wall temperature during flow boiling is represented. The wall temperature during liquid-phase flow is identical in the radial direction and increases linearly in the axial direction. The wall temperature exhibits significant axially as well as radially variation in two-phase flow. The wall temperature fluctuates vigorously in mini-channels. The influence of subatmospheric system pressure on subcooled flow boiling is examined in the conventional channel with a diameter of 11.7 mm. An increase in the subcooled flow boiling heat transfer coefficient is observed when the system pressure is lower than atmospheric pressure. At subatmospheric system pressure, the wall temperature exhibits radial symmetry across all Froude number values. Furthermore, the mass flux does not significantly impact the subcooled boiling heat transfer coefficient, when subjected to constant heat flux.

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Experimental investigation of pressure drop in helical coil during flow boiling at subatmospheric pressures

et al. 2023

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Heat transfer distribution and pressure fluctuations during flow boiling in a pipe with different orientations

Cited by 11 publications

References 33 publications

Effect of flow direction on heat transfer and flow characteristics of supercritical carbon dioxide

Effect of flow direction on heat transfer and flow characteristics of supercritical carbon dioxide

Heat Transfer And Wall Temperature Distribution During Flow Boiling In Conventional And Mini Channels

Experimental investigation of pressure drop in helical coil during flow boiling at subatmospheric pressures

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