A model of heat transfer coefficient for supercritical water considering the effect of heat transfer deterioration

Li, Fangbo; Bai, Bofeng

doi:10.1016/j.ijheatmasstransfer.2018.12.121

Cited by 26 publications

(9 citation statements)

References 31 publications

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“…[29] which has similar working conditions, the dimensionless excess temperature exceeds 0.9 at δ + = 300 in the tube turbulence (for details, see Ref. [11]). For simplicity, the authors assumed an approximate value of 300 for δ + , and then the expression of δ can be expressed as…”

Section: Correlation By LI and Baimentioning

confidence: 95%

“…This case describes the upward flow of supercritical water in a circular tube with an inner diameter of 26 mm and heated length of 2.0 m. Data in this figure come from Ref. [11].…”

Section: Correlation By Jacksonmentioning

confidence: 99%

“…Li and Bai [11] proposed a semiempirical correlation based on the momentum and energy integration equations in the thermal boundary layer. The authors observed the direct numerical simulation (DNS) data under deteriorated HT regime in Bae et al [7], Hu [27], Peeters et al [28], and Zhang et al [29], and they found that in the turbulent core, the temperature gradient is negligible; therefore, the fluid temperature in the core is approximately the bulk temperature, especially when T b < T pc < T w .…”

Section: Correlation By LI and Baimentioning

confidence: 99%

“…This can be explained as follows: the fluid within the pseudo-critical region absorbs considerable energy due to the high c p , leading to the small temperature gradient in the turbulent core [7]. Based on these characteristics, Li and Bai built a "two-layer model" for deteriorated HT (as is shown in Figure 6) [11,30]. The turbulence in the tube is divided into two layers: the thermal boundary layer and the core layer.…”

Section: Correlation By LI and Baimentioning

confidence: 99%

“…It is shown that the predictions on the mixing convection cases can be improved by this method. In order to further improve the performances of the empirical correlations under the strong buoyancy effect, some researchers tried to establish the semiempirical correlations based on the theoretical analysis approaches [11,12]. The existing semiempirical correlations mainly aim to derive the qualitative relationship between the heat transfer impairment and turbulent shear stress reduction; the coefficients appeared in the correlation are obtained by fitting the experimental data.…”

Section: Introductionmentioning

confidence: 99%

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Heat Transfer Correlations of Supercritical Fluids

Li¹,

Pei²,

Bai³

2020

Advanced Supercritical Fluids Technologies

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The drastic changes of thermophysical properties in the pseudo-critical region of supercritical fluids bring very big challenges to the traditional Dittus-Boeltertype heat transfer correlations. In this chapter, we will talk about the principles and applications of two kinds of heat transfer correlations of supercritical fluids: the empirical type and the semiempirical type. For the empirical correlations, the modification methods taking into account the variable properties and body force effects will be introduced. We will focus on the proposal of nondimensional parameters describing the buoyancy effect and flow acceleration; while for the semiempirical ones, we mainly talk about the new kind of correlation which is based on the momentum and energy conservations in the mixed convective flow.

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Section: Correlation By LI and Baimentioning

confidence: 95%

“…This case describes the upward flow of supercritical water in a circular tube with an inner diameter of 26 mm and heated length of 2.0 m. Data in this figure come from Ref. [11].…”

Section: Correlation By Jacksonmentioning

confidence: 99%

Section: Correlation By LI and Baimentioning

confidence: 99%

Section: Correlation By LI and Baimentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Heat Transfer Correlations of Supercritical Fluids

Li¹,

Pei²,

Bai³

2020

Advanced Supercritical Fluids Technologies

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High‐heat flux flow and heat transfer transitions in a supercritical loop: Numerical verification and correlation

Yang

Lin

Chen

et al. 2021

Intl J of Energy Research

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Summary Supercritical heat transfer loops are widely used in large‐scale thermal equipment, which development is restricted by the thermal‐hydraulic characteristics, especially the safety and thermal efficiency under high‐heat fluxes. This study is focused on numerical simulation for a 4‐m test section of the loop and further analyzes the flow transitions and heat transfer mechanisms from subcritical to supercritical. The heat transfer characteristics of supercritical water in the vertical loop were simulated for conditions: P = 24 MPa, Tin = 320°C, 340°C, mass flux (G) = 1000 kg/m2s, 1500 kg/m2s, and heat fluxes varied from 100 to 1200 kW/m2. The heat transfer transitions are analyzed from the perspective of local parameters that affect the status of both core flow and boundary layers. The empirical correlation and the error backpropagation (BP) neural network prediction model are proposed and compared with experimental and numerical results. The results show that transitions of both boundary layer and core flow from subcritical to supercritical contribute to the heat transfer behaviors: normal heat transfer, heat transfer deterioration, and heat transfer enhancement. The zero‐velocity gradient (∂u/∂r = 0) on the M‐shaped velocity curve causes the turbulent shear stress near the wall to be close to zero, which leads to the suppression of the turbulence. At the same time, the thickness of the thermal boundary layer reaches the maximum, resulting in a large thermal resistance, which affects the heat transfer from the wall to the core area.

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