Investigation and Modeling of the In-Tube Heat Transfer of Fluids at Supercritical Pressure During Heating

2017 ◽  
Author(s):  
Chen-Ru Zhao ◽  
Zhen Zhang ◽  
Han-Liang Bo ◽  
Pei-Xue Jiang
Keyword(s):  
Heat Transfer ◽  
Numerical Modelling ◽  
Convection Heat Transfer ◽  
Turbulence Models ◽  
Vertical Tube ◽  
Supercritical Pressure ◽  
Flow And Heat Transfer ◽  
Pressure Water ◽  
Predicted Values ◽  
Semi Empirical

Investigations and numerical modelling are performed on the heat transfer to CO2 at supercritical pressure under buoyancy affected conditions during heating in a vertical tube with inner diameter of 2 mm. Numerical modelling are carried out using several low Reynolds number (LRN) k-ε models, including the model due to Launder and Sharma (LS), Abe, Kondoh and Nagano (AKN), Myong and Kasagi (MK) models. The numerical results are compared with the corresponding experimental data and the predicted values using the semi-empirical correlation for convection heat transfer of supercritical fluids without deterioration. The abilities of various LRN models to predict the heat transfer to fluids at supercritical pressures under normal and buoyancy affected heat transfer conditions are evaluated. Detailed information related to the flow and turbulence is presented to get better understanding of the mechanism of the heat transfer deterioration due to buoyancy, as well as the different behavior of various LRN turbulence models in responding to the buoyancy effect, which gives clues in future model improvement and development to predict the buoyancy affected heat transfer more precisely and in a broader range of conditions as they come to be used to simulate the flow and heat transfer in various applications such as in the supercritical pressure water-cooled reactor (SCWR) and the supercritical pressure steam generator in the high temperature gas cooled reactor (HTR).

A Computational Study of Convection Heat Transfer to CO2 at Supercritical Pressures in a Vertical Mini Tube

2004 ◽  
Author(s):  
S. He ◽  
P. X. Jiang ◽  
Yi-Jun Xu ◽  
Run-Fu Shi ◽  
W. S. Kim ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Eddy Viscosity ◽  
Computational Study ◽  
Convection Heat Transfer ◽  
Turbulence Models ◽  
Vertical Tube ◽  
Convection Heat ◽  
Flow Acceleration ◽  
Turbulence Production ◽  
The One

Computational simulations of experiments on turbulent convection heat transfer of carbon dioxide at supercritical pressures in a vertical tube of diameter 0.948 mm have been carried out using low-Reynolds number eddy viscosity turbulence models. The simulations were able to reproduce the general features exhibited in the experiments. The modelling study has provided valuable information on the detailed flow and turbulence fields. It has been shown that for mini tubes such as the one used in the current study, the buoyancy effect is generally insignificant. Heat transfer can be significantly impaired when the heating is strong. This is due to the reduced turbulence production, induced by the flow acceleration which is in turn caused by strong heating.

Direct numerical simulation of convective heat transfer of supercritical pressure in a vertical tube with buoyancy and thermal acceleration effects

2021 ◽  
Vol 927 ◽  
Author(s):  
Y.L. Cao ◽  
R.N. Xu ◽  
J.J. Yan ◽  
S. He ◽  
P.X. Jiang
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Turbulent Flow ◽  
Vertical Tube ◽  
Supercritical Pressure ◽  
Dominant Factor ◽  
Turbulent Structures ◽  
Flow Acceleration ◽  
Flow And Heat Transfer

Supercritical pressure fluids are widely used in heat transfer and energy systems. The benefit of high heat transfer performance and the successful avoidance of phase change from the use of supercritical pressure fluids are well-known, but the complex behaviours of such fluids owing to dramatic thermal property variations pose strong challenges to the design of heat transfer applications. In this paper, the turbulent flow and heat transfer of supercritical pressure $\textrm {CO}_2$ in a small vertical tube influenced by coupled effects of buoyancy and thermal acceleration are numerically investigated using direct numerical simulation. Both upward and downward flows with an inlet Reynolds number of 3540 and pressure of 7.75 MPa have been simulated and the results are compared with corresponding experimental data. The flow and heat transfer results reveal that under buoyancy and thermal acceleration, the turbulent flow and heat transfer exhibit four developing periods in which buoyancy and thermal acceleration alternately dominate. The results suggest a way to distinguish the dominant factor of heat transfer in different periods and a criterion for heat transfer degradation under the complex coupling of buoyancy and thermal acceleration. An analysis of the orthogonal decomposition and the generative mechanism of turbulent structures indicates that the flow acceleration induces a stretch-to-disrupt mechanism of coherent turbulent structures. The significant flow acceleration can destroy the three-dimensional flow structure and stretch the vortices resulting in dissipation.

Performance of a variety of low Reynolds number turbulence models applied to mixed convection heat transfer to air flowing upwards in a vertical tube

2004 ◽  
Vol 218 (11) ◽  
pp. 1361-1372 ◽  
Author(s):  
W S Kim ◽  
J D Jackson ◽  
S He ◽  
J Li
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Mixed Convection ◽  
Low Reynolds Number ◽  
Convection Heat Transfer ◽  
Turbulence Models ◽  
Vertical Tube ◽  
Convection Heat ◽  
Mixed Convection Heat Transfer ◽  
Low Reynolds

The study reported here is concerned with mixed convection heat transfer to air flowing upwards in a vertical tube. Computational simulations of experiments from a recent investigation have been performed using an ‘in-house’ code which was written specifically for variable-property, developing, buoyancy-influenced flow and heat transfer in a vertical passage. The code incorporates a selection of two-equation, low Reynolds number turbulence models. The objective of the study was to evaluate the models in terms of their capability of reproducing the effects on turbulent heat transfer of non-uniformity of fluid properties and buoyancy. Direct comparisons have been made between results from the experimental investigation and those obtained by computational modelling for a range of conditions. The trends of impairment and enhancement of heat transfer owing to the influence of buoyancy found in the experiments were captured to some extent in the simulations using each of the models. However, none reproduced observed behaviour correctly over the entire range of buoyancy influence.

Study of the Effect of Buoyancy on Flow and Heat Transfer of Supercritical Pressure Water in Horizontal Pipes

2011 ◽  
Author(s):  
Shuiqing Yu ◽  
Huixiong Li ◽  
Xianliang Lei ◽  
Yifan Zhang ◽  
Tingkuan Chen
Keyword(s):  
Heat Transfer ◽  
Specific Heat ◽  
Local Heat Transfer ◽  
Supercritical Pressure ◽  
Buoyancy Effect ◽  
Transfer Coefficients ◽  
Horizontal Pipes ◽  
Flow And Heat Transfer ◽  
Pressure Water ◽  
Supercritical Pressure Water

The present paper is devoted to clarify the effect of buoyancy on the flow and heat transfer of supercritical pressure water flowing in horizontal pipes at supercritical pressures. A series of experiments have been designed and carried out in Xi’an Jiaotong University, Xi’an, China to obtain data in relation to flow and heat transfer of supercritical pressure water in pipes with different arrangements. The experimental parameters are as follows: pressures ranging from 23 to 28MPa, heat flux being up to 600 kW/m2, and the fluid mass fluxes being in the range from 100 to 1000kg/(m2s). In this study, distributions of the local wall temperatures and the local heat transfer coefficients around the circumference of the tube are measured at different cross-sections along the flowing direction. On the basis of the experimental data obtained in the study, some criteria available in open literatures, including Gr/Re2.7, Gr/Re2, and Grq/Grth, are employed to estimate the magnitude of buoyancy and the effect of buoyancy on the flow and heat transfer behavior of the supercritical fluid. It is showed that buoyancy is of particular importance for horizontal flows, but play significantly different role in different regions having different characteristics of the specific heat capacity. Strong buoyancy effect exists in the large specific heat region, but in the enthalpy region which is far away from the LSHR, the discrepancy between the temperature of the top wall and that of the bottom wall is small, indicating that the buoyancy effect can be negligible. Based on the present study, it was found that the criteria Grq/Grth is better than others in terms of the capability of evaluating the effect of the buoyancy on the flow and heat transfer of supercritical water.

Simulation of mixed convection heat transfer to carbon dioxide at supercritical pressure

2004 ◽  
Vol 218 (11) ◽  
pp. 1281-1296 ◽  
Author(s):  
S He ◽  
W S Kim ◽  
P X Jiang ◽  
J D Jackson
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Carbon Dioxide ◽  
Mixed Convection ◽  
Convection Heat Transfer ◽  
Turbulence Models ◽  
Supercritical Pressure ◽  
Convection Heat ◽  
Computational Simulations ◽  
Mixed Convection Heat Transfer

Computational simulations of turbulent mixed convection heat transfer experiments using carbon dioxide at supercritical pressure have been performed by solving the Reynolds averaged transport equations using an elliptic formulation. A number of two-equation low Reynolds number turbulence models have been used and the results have been compared directly with the experimental data. It has been shown that most of the models were to some extent able to reproduce the effects of the very strong influences of buoyancy on heat transfer in these experiments. However, the performance of the models varied significantly from one to another in terms of the predicted onset of such effects.

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