Critical heat flux in a closed two-phase thermosyphon

Imura, Hidefumi; Sasaguchi, Kengo; Kozai, Hiroaki; Numata, Shohei

doi:10.1016/s0017-9310(83)80172-0

Cited by 180 publications

(47 citation statements)

References 5 publications

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“…Since the aspect ratio (L/D) of the TPCT becomes larger with a smaller diameter, the axial heat flux increases at the same heat transfer rate, which is liable to cause flooding limit. It accords with the acknowledged conclusion that the performance is generally limited by flooding limit in a TPCT with comparatively large values of aspect ratio [1,24]. Figure 11 shows the effect of the condenser length.…”

Section: The Closed Operation Range Of a Vertical Tpctsupporting

confidence: 84%

“…With a very large filling ratio, the twophase mixture in liquid pool could be extended to condenser. Under this condition, the heat transfer performance is deteriorated and periodic burst boiling takes place, which causes vibration of the TPCT accompanied by a bursting noise [1]. Moreover, its performance is also restricted by the heat transfer limit.…”

Section: Introductionmentioning

confidence: 99%

“…Kutateladze's correlation is based on the stability criterion in two-phase flow, with the effects of fluid inertia force, buoyancy, surface tension and without the effect of diameter. By taking advantage of the two types, some studies [1,[7][8][9][10] have been reported to further develop the correlation for flooding limit. Based on experimental data, Gorbis et al [11] and Bezrodnyi et al [12] provided their correlations for boiling limit, respectively.…”

Section: Introductionmentioning

confidence: 99%

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Determination of the operation range of a vertical two-phase closed thermosyphon

Qiu

Gan

et al. 2012

Heat Mass Transfer

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A comprehensive model, proposed for a vertical two-phase closed thermosyphon (TPCT) by the present authors, is further developed by utilizing the criteria for dryout, flooding and boiling limits to investigate the effects of filling ratio on them together, while the available models can just consider one or two limits of them. A new concept named dryout ratio is proposed, which can be used for predicting dryout limit. The empirical correlation and the empirical value, provided by other researchers, are used for predicting flooding and boiling limit, respectively. The experiments with nitrogen as working fluid are performed, and compared with the calculations. The maximum filling ratio is introduced, beyond which the liquid could be carried to condenser and the heat transfer performance can be deteriorated. And then the closed operation range of a vertical TPCT is finally determined, which has not been reported before. The effects of operating pressure and geometries on the range are also analyzed. List of symbolsHeat transfer rate (W) qRadial heat flux (W m -2 ) ReReynolds number T Temperature (K) uFlow velocity (m s -1 ) V vj Vapor drift velocity (m s -1 ) xAxial coordinate y Radial coordinateGreek symbols d Liquid film thickness (m) r Surface tension (N m -1 ) q Density (kg m -3 ) a Void fraction l Dynamic viscosity (Pa s) m Kinematic viscosity (m 2 s -1 ) s Shear stress (N m -2 ) k Thermal conductivity (W m -1 K -1 ) C Mass flow rate per unit width (Kg m -1 s -1 )

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Section: The Closed Operation Range Of a Vertical Tpctsupporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Determination of the operation range of a vertical two-phase closed thermosyphon

Qiu

Gan

et al. 2012

Heat Mass Transfer

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“…The known causes of the heat and mass transfer crisis [6][7] are breakdown of condensate from the thermosyphon walls, limiting steam content in the wall layer, formation of dry spots on the internal surface of the evaporator. Determination of the critical heat flux density 2 , / cr q kW m at which the heat and mass transfer crisis occurs is necessary to calculate the minimum filling ratio of a thermosyphon with the coolant.…”

Section: Introductionmentioning

confidence: 99%

Critical heat flux density in diphasic thermosyphons

2017

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Abstract. The paper presents an analysis of known dependencies for determining the critical heat flux density in diphasic thermosyphons. The critical heat flux density for the created experimental model of thermosyphon were calculated on the basis of the theoretical contributions of 1) the occurrence of a "flooding" regime in a thermosyphon characterized by a disturbance of the hydrodynamic stability of the phase interface and the entrainment of the liquid phase by the gas flow; 2) the mutual influence of gravitational forces and surface tension; 3) S.S. Kutateladze hydrodynamic theory of the heat transfer crisis during boiling. It is found that the existing theoretical contributions which can be used to calculate the critical heat flux density and subsequently determine the minimum filling ratio of a thermosyphon are conditionally applicable.

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“…CHF is a phenomenon which is of practical importance for many industrial devices such as nuclear reactors, boilers, steam generators, superconducting magnets, electronic equipment, rocket engines and so on. Accordingly, numerous and extensive experimental and analytical research works have been carried out, and many aspects of the CHF have been understood to some extent and some predicting methods have been developed based on experimental data for many years [2][3][4][5][6]. Table 1 lists some correlations for predicting the CHF in concentric-tube open thermosiphon.…”

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confidence: 99%

Predicting the critical heat flux in concentric-tube open thermosiphon: a method based on support vector machine optimized by chaotic particle swarm optimization algorithm

Cai

2012

Heat Mass Transfer

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This study presents a method based on support vector machine (SVM) optimized by chaotic particle swarm optimization algorithm (CPSO) for the prediction of the critical heat flux (CHF) in concentric-tube open thermosiphon. In this process, the parameters C, e and d 2 of SVM have been determined by the CPSO. As for a comparision, the traditional back propagation neural network (BPNN), radial basis function neural network (RBFNN), general regression neural network (GRNN) are also used to predict the CHF for the same experimental results under a variety of operating conditions. The MER and RMSE of SVM-CPSO model are about 45% of the BPNN model, about 60% of the RBFNN model, and about 80% of GRNN model. The simulation results demonstrate that the SVM-CPSO method can get better accuracy. Abbreviations ANNArtificial neural network BPNN Back propagation neural network CPSO Chaotic particle swarm optimization algorithm D he Equivalent heated diameter, (D i 2 -d o 2 )/D i D i

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Critical heat flux in a closed two-phase thermosyphon

Cited by 180 publications

References 5 publications

Determination of the operation range of a vertical two-phase closed thermosyphon

Determination of the operation range of a vertical two-phase closed thermosyphon

Critical heat flux density in diphasic thermosyphons

Predicting the critical heat flux in concentric-tube open thermosiphon: a method based on support vector machine optimized by chaotic particle swarm optimization algorithm

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