Experimental studies on heat transfer to supercritical water in circular tubes at high heat fluxes

Gu, Haihua; Zhao, Meng; Xu, Cheng

doi:10.1016/j.expthermflusci.2015.03.001

Cited by 59 publications

(5 citation statements)

References 11 publications

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“…The experimental data in the papers of Mokry et al [7] and Gu et al [10] were used for the comparison, with the fluid-flowing upwards in a uniformly heated vertical tube. The test section was a circular tube with an inner diameter of 10 mm, the heated length is 4000 mm and 2500 mm for the experiment of Mokry et al [7] and Gu et al [10], respectively. The working fluid was supercritical water and the experiment pressure was 23.0, 24.1, and 25.0 MPa.…”

Section: Experimental Datamentioning

confidence: 99%

“…Besides, density will change with the variation of the axial temperature and pressure, McEligot and Jackson [4] and Jiang et al [5] proposed nondimensional parameters, Kv T and Kv P , to evaluate the influence of the thermal acceleration induced by axial temperature variation and the influence of flow acceleration induced by the axial pressure, respectively. In addition, the effect of heat flux, mass-flow rate and diameter on the convective heat transfer of supercritical fluid in vertical heated circular tubes were investigated as well [5][6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

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Discussion on improved method of turbulence model for supercritical water flow and heat transfer

Wang

2020

Therm sci

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The turbulence model fails in supercritical fluid-flow and heat transfer simulation, owing to the drastic change of thermal properties. The inappropriate buoyancy effect model and the improper turbulent Prandtl number model are several of these factors lead to the original low-Reynolds number turbulence model unable to predict the wall temperature for vertically heated tubes under the deteriorate heat transfer conditions. This paper proposed a simplified improved method to modify the turbulence model, using the generalized gradient diffusion hypothesis approximation model for the production term of the turbulent kinetic energy due to the buoyancy effect, using a turbulence Prandtl number model for the turbulent thermal diffusivity instead of the constant number. A better agreement was accomplished by the improved turbulence model compared with the experimental data. The main reason for the over-predicted wall temperature by the original turbulence model is the misuse of the buoyancy effect model. In the improved model, the production term of the turbulent kinetic energy is much higher than the results calculated by the original turbulence model, especially in the boundary-layer. A more accurate model for the production term of the turbulent kinetic energy is the main direction of further modification for the low Reynolds number turbulence model.

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Section: Experimental Datamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Discussion on improved method of turbulence model for supercritical water flow and heat transfer

Wang

2020

Therm sci

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“…Similar supercritical heat transfer cases for upward flow were simulated to better understand the heat transfer mechanisms and as the first step to develop a dimensionless number to describe the heat transfer characteristics. Similar supercritical heat transfer experimental data sets for water and R134a were selected by using the scaling law of Cheng et al as listed in Table . Cases H 2 O‐01 and R134a‐01 are forced convection flow conditions, while cases H 2 O‐02 and R134a‐02 are mixed convection flow conditions with buoyancy effects.…”

Section: Numerical Heat Transfer Analyses With Water and R134amentioning

confidence: 99%

“…Heat transfer to supercritical pressure fluids is a key issue studied in many engineering applications such as the supercritical water‐cooled reactor, supercritical boilers, and supercritical organic Rankine cycles (ORCs) . Many researchers have conducted experiments with water to investigate the heat transfer characteristics for the supercritical water‐cooled reactor and supercritical boilers . Since the critical temperature and pressure of water are extremely high, model fluids such as carbon dioxide and Freon are used to scale down the experimental parameters to reduce the difficulty and cost.…”

Section: Introductionmentioning

confidence: 99%

Fluid-to-fluid scaling of heat transfer to mixed convection flow of supercritical pressure fluids

et al. 2018

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Summary Fluid‐to‐fluid scaling for supercritical heat transfer can effectively reduce the difficulty and cost of heat transfer experiments in supercritical boilers and supercritical water reactors and can reduce the number of experiments by converting experimental data of the model fluid to the prototype fluid in organic Rankine cycles. Currently, most existing scaling methods are only suitable for forced convection, while few are developed for mixed convection where buoyancy significantly affects the heat transfer. This paper attempts to extend the applicability of scaling method to mixed convection with the aid of computational fluid dynamic simulations. The scaling parameters were analyzed first and then the shear‐stress transport k‐ω model was used to analyze the supercritical heat transfer characteristics of water and R134a to provide further information for developing a dimensionless number. The results show that significant variations of properties and flow parameters occur in the layer of y+ = 5 to 100 and the axial velocity gradient in this layer changes in quite a similar manner to the wall temperature. Based on numerical results, the axial velocity gradient was used with a thermal resistance analogy to derive a new dimensionless number, Re−0.9πA, to scale the mass flux. Then, a set of fluid‐to‐fluid scaling laws were developed to predict the heat transfer to supercritical fluids. To validate the newly proposed scaling laws, well‐developed correlations were used for forced convection flow and a direct validation method was developed for buoyancy‐influenced flow. Results show that this new scaling method exhibits reasonable accuracy for both forced and mixed convection heat transfer with supercritical fluids.

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“…A series of experimental studies on convection heat transfer of supercritical pressure fluid has been completed [5][6], and the thermal hydraulic phenomenon in the loop is measured simultaneously visualized by dynamic neutron radiography techniques [7]. More recent experimental heat transfer studies have been carried out by Pis'menny [8], Gu [9], Licht et al [10], and Mokry et al [11] under conditions of supercritical water in circular tubes at high heat fluxes. Convection heat transfer of supercritical carbon dioxide in vertical heated circular tubes with different interior diameters have been carried out by Jiang et al [12][13][14], Zhao et al [15], and Song et al [16].…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation of Heat Transfer to Supercritical Water in Vertical Tube under Semicircular Heating Condition

Wang

2019

Energies

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In-depth understanding and analysis of turbulent convection heat transfer of supercritical water under semicircular heating conditions play a major role in system design and security. The inaccurate numerical results on simulating the buoyancy effect under deterioration heat transfer cases are partly attributed to the invalidity of the turbulent model. An improved turbulence model, which is validated suitable to three-dimensional model, is adopted in the present paper to numerical simulated flow and heat transfer in a vertical tube under semicircular heating condition. Heat transfer deterioration phenomenon occurs under semicircular heating condition, while the degree of deterioration is weakened due to the influence of variable physical properties and buoyancy effect. The velocity profile is distorted into “M-shape” in the heating side and present parabolic distribution in the adiabatic side, leading to different deterioration mechanisms under semicircular heating condition compared with uniform heating. The larger density difference between the heating side and the adiabatic side increases the shear stress production of turbulent kinetic energy; turbulent development is much faster recovery than the phenomenon in uniform heating condition. The results show that the semicircular heating condition can effectively alleviate the degree of heat transfer deterioration in a vertical tube.

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Experimental studies on heat transfer to supercritical water in circular tubes at high heat fluxes

Cited by 59 publications

References 11 publications

Discussion on improved method of turbulence model for supercritical water flow and heat transfer

Discussion on improved method of turbulence model for supercritical water flow and heat transfer

Fluid-to-fluid scaling of heat transfer to mixed convection flow of supercritical pressure fluids

Numerical Investigation of Heat Transfer to Supercritical Water in Vertical Tube under Semicircular Heating Condition

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