Numerical Analysis of Thermal-Hydraulic Behavior of Supercritical Water in Vertical Upward/Downward Flow Channels

2008 ◽  
Author(s):  
Hanyang Gu ◽  
Xu Cheng ◽  
Xiaojing Liu
Keyword(s):  
Heat Transfer ◽  
Numerical Analysis ◽  
Supercritical Water ◽  
Square Lattice ◽  
Bulk Temperature ◽  
Upward Flow ◽  
Downward Flow ◽  
Hydraulic Behavior ◽  
Hydraulic Behaviour ◽  
Turbulence Mixing

Investigations on the thermal-hydraulic behavior in the SCWR fuel assembly have obtained a significant attention in the international SCWR community. However, there is still a lack of understanding and ability to predict the heat transfer behavior of supercritical fluids. In this paper, the numerical analysis is carried out to study the thermal-hydraulic behaviour in vertical sub-channels cooled by supercritical water. Remarkable differences in characteristics of secondary flow are found, especially in square lattice, between the upward flow and downward flow. The turbulence mixing across sub-channel gap for downward flow is much stronger than that for upward flow in wide lattice when the bulk temperature is lower than pseudo-critical point temperature. For downward flow, heat transfer deterioration phenomenon is suppressed with respect to the case of upward flow at the same conditions.

Experiment of Heat Transfer to Supercritical Water Flowing in Vertical Annular Channels

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Zhendong Yang ◽  
Qincheng Bi ◽  
Han Wang ◽  
Gang Wu ◽  
Richa Hu
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Flux ◽  
Supercritical Water ◽  
Experimental Parameter ◽  
Outer Diameter ◽  
Buoyancy Effect ◽  
Upward Flow ◽  
Downward Flow ◽  
Annular Channels

An experimental study of heat transfer to supercritical water has been performed at Xi'an Jiaotong University with a vertical annular tube. The annular test sections were constructed with an annular gap of 2 mm and an internal heater of 8 mm outer diameter. Experimental parameter covered pressures of 23 and 25 MPa, mass fluxes of 700 and 1000 kg/m2s, and heat fluxes of 200–1000 kW/m2. Experimental data were acquired from downward flow and upward flow, respectively. There were differences of heat-transfer characteristics between the two flow directions. Compared to upward flow, the heat-transfer coefficient increased at downward flow. A strong effect of spacer on heat transfer is observed at locations downstream of the device in the annuli regardless of flow direction. The spacer effect impaired the buoyancy effect at low heat flux, but not for large heat flux. Complex of forced convection and mixed convection in supercritical water is due to various thermophysical properties and the gravity. The affected zone of the spacer effect depends on the flow conditions. The buoyancy effect was analyzed qualitatively in this study and the criterion Gr¯/Re2.7<10-5 for negligible heat-transfer impairment was discussed. Four correlations were compared with the experimental data; the Swenson correlation predicted nearly the experimental data but overpredicted slightly the heat-transfer coefficients.

Heat Transfer to Supercritical Water in Gaseous State or Affected by Mixed Convection in Vertical Tubes

2006 ◽  
Author(s):  
E. N. Pis’menny ◽  
V. G. Razumovskiy ◽  
E. M. Maevskiy ◽  
A. E. Koloskov ◽  
I. L. Pioro
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Supercritical Water ◽  
Operating Conditions ◽  
Maximum Effect ◽  
Upward Flow ◽  
Downward Flow ◽  
Gaseous State ◽  
Transfer Data ◽  
Vertical Tubes

The results on heat transfer to supercritical water heated above the pseudocritical temperature or affected by mixed convection flowing upward and downward in vertical tubes of 6.28-mm and 9.50-mm inside diameter are presented. Supercritical water heat-transfer data were obtained at a pressure of 23.5 MPa, mass flux within the range from 250 to 2200 kg/(m2s), inlet temperature from 100 to 415°C and heat flux up to 3.2 MW/m2. Temperature regimes of the tubes cooled with supercritical water in a gaseous state (i.e., supercritical water at temperatures beyond the pseudocritical temperature) were stable and easily reproducible within a wide range of mass and heat fluxes. An analysis of the heat-transfer data for upward and downward flows enabled to determine a range of Gr/Re2 values corresponding to the maximum effect of free convection on the heat transfer. It was shown that: 1) the heat transfer coefficient at the downward flow of water can be higher by about 50% compared to that of the upward flow; and 2) the deteriorated heat-transfer regime is affected with the flow direction, i.e., at the same operating conditions, the deteriorated heat transfer may be delayed at the downward flow compared to that at the upward flow. These heat-transfer data are applicable as the reference dataset for future comparison with bundle data.

ICONE23-1163 CFD MODELING OF SUPERCRITICAL WATER HEAT TRANSFER IN A VERTICAL BARE TUBE UPWARD FLOW

2015 ◽  
Vol 2015.23 (0) ◽  
pp. _ICONE23-1-_ICONE23-1 ◽  
Author(s):  
Vladimir Agranat ◽  
Michael Malin ◽  
Igor Pioro ◽  
Rand Abdullah ◽  
Valery A. Perminov
Keyword(s):  
Heat Transfer ◽  
Supercritical Water ◽  
Cfd Modeling ◽  
Upward Flow ◽  
Bare Tube

Numerical Investigation of Heat and Mass Flux Effects on Heat Transfer Characteristics of Supercritical Water in an Upward Flow Vertical Tube

2014 ◽  
Vol 592-594 ◽  
pp. 1667-1671
Author(s):  
T. Vinoth ◽  
K. Karuppasamy ◽  
D. Santhosh Kumar ◽  
R. Dhanuskodi
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Flux ◽  
Supercritical Water ◽  
Mass Flux ◽  
Vertical Tube ◽  
Upward Flow ◽  
Heat Transfer Characteristics ◽  
Ansys Fluent ◽  
Transfer Characteristics

In the present work, the heat transfer characteristics of supercritical pressure water are numerically investigated in an upward flow vertical smooth tube. The numerical simulations are carried out by using Ansys-Fluent solver. The objective of the present work is to investigate the effect of heat flux and mass flux on heat transfer characteristics in supercritical water. In order to perform numerical simulation, experimental data of Mokryet al.[2] is considered. Various simulations were carried out for the inlet parameters of temperature 350°C, pressure 240bar; heat flux values ranging from 190 to 884kW/m2and mass flux values ranging from 498 to 1499kg/m2s. Based on the available parameters of heat flux and mass flux, they are segregated as groups with heat flux to mass flux ratios of 0.39 and 0.67. According to computational data, the heat transfer enhancement and heat transfer deterioration phenomenon of supercritical water were analyzed and based on the comparison with experimental data; their occurrence and mechanism were addressed.

Numerical Analysis of Supercritical Water Heat Transfer in Vertical Tube With Different Obstacles

2009 ◽  
Author(s):  
Bo Zhang ◽  
Jianqiang Shan ◽  
Jing Jiang
Keyword(s):  
Heat Transfer ◽  
Critical Point ◽  
Supercritical Water ◽  
Transfer Characteristic ◽  
Vertical Tube ◽  
Bulk Temperature ◽  
Transfer Enhancement ◽  
Heat Transfer Characteristics ◽  
Water Reactors ◽  
The Heat Transfer Coefficient

Supercritical Water Reactors (SCWRs) are essentially water reactors operating at pressure and temperature above critical point. The heat transfer coefficient is relative low when the bulk temperature is above the pseudo-critical point due to the properties of vapor-like fluid. To obtain better heat transfer characteristics, increasing the fluctuation using obstacles is the conventional method. Heat transfer characteristic in vertical tube with different obstacles is numerically investigated under supercritical condition. Numerical simulation is carried out with commercial CFD code Fluent 6.1 and adaptive grid. The results show that The RNG k-ε model with enhanced wall treatment can obtain a reliable result; the blockage ratio and the local temperature have large influence on the heat transfer enhancement. The influence region and decay trend of obstacles are also studied and compared with existing correlations.

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