A Critical Review on Heat Transfer of Supercritical Fluids

Wang, Qingyang; Xu, Jinliang; Zhang, Chengrui; Hao, Bingtao; Cheng, Lixin

doi:10.1080/01457632.2022.2164684

Cited by 12 publications

(4 citation statements)

References 170 publications

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“…对于水平管, 当热流密度为178.3 kW/m 2 时, 底母线内壁温在拟临界点附近随热流的增长趋势较为平缓, 这是因为工质热力学干度较低 [30] , 横截面内工质大部分处于拟临界点附近, 比热较大, 工质携带热量的能力较强, 内壁温上升较慢. Zhang等 [8] 发现垂直向上管传热恶化时会产生额外的阻力压温差逐渐减小, 这是流速增大导致惯性力的增大 [23] , 热物性随压力的变化不如底母线的LL工质敏感 [31] .…”

Section: 正常传热和传热恶化下的传热特性unclassified

“…对于垂直向上管中, f呈现两种分布, 在正常传热下比较小, 当SBO > 5.126×10 -4 时, 传热模式变为传热恶化, 摩擦因子急剧增加. Zhang等 [8] 认为这与近壁VL流体形成孔口收缩效应有关. 在水平管中, f不再依赖SBO数, 大小与垂直管传热恶化时的f相近.…”

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

“…当质量流量较高时, 惯性力作用远高于二次流的作用, 所以如图4(b)所示两者阻力压降几乎相同. 对于垂直向上管: 阻力压降ΔP f 主要来自近壁面的VL膜和管芯LL工质相互作用和孔口收缩效应引发的压头降落 [8] , 当压力增大时, This work is devoted to investigating the difference in flow and heat transfer characteristics between vertical upward flow and horizontal flow of supercritical carbon dioxide ( ) based on the pseudo-boiling theory and the experimental parameters: mass flux G = 496-1100 kg/m 2 s, heat flux q w = 54.4-300.2 kW/m 2, and pressure P = 7.531-20.513 MPa. The differences in flow and heat transfer characteristics between horizontal upward tube and vertical upward tube are compared at different mass fluxes, heat fluxes and pressures fully.…”

Section: 两管的阻力压降差异可能归因于Vl与ll工mentioning

confidence: 99%

“…实验段采用规格为 φ8 mm×2 mm的 1 Cr18 Ni9 Ti不锈钢圆管 , 总长3600 mm, 其中加热段长度为2000 mm. 实验段几何结构和测温点布置如图1(a)所示, 垂直段几何结构和测温点布如图1(b)所示 [8] . 进出口工质温度采用直径1 mm的NiCr-Nisi护套热电偶.…”

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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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