Flow distribution investigation and sensitive analyses on reverse flow in U-tubes of steam generator under natural circulation

2021 ◽  
Vol 154 ◽  
pp. 108112
Author(s):  
Wei Shi ◽  
Feng Yi ◽  
Pengcheng Zhao ◽  
Tianshi Wang ◽  
Yuqing Wang
Keyword(s):  
Steam Generator ◽  
Reverse Flow ◽  
Natural Circulation ◽  
Flow Distribution

Flow Reversal in a Horizontal Type Natural Circulation Heat Recovery Steam Generator

2006 ◽  
Author(s):  
Heimo Walter ◽  
Wladimir Linzer
Keyword(s):  
Steam Generator ◽  
Heat Recovery ◽  
Reverse Flow ◽  
Natural Circulation ◽  
Heating Surface ◽  
Heat Absorption ◽  
System Pressure ◽  
Horizontal Type ◽  
The Stability ◽  
The Individual

Natural circulation heat recovery steam generators (HRSG) are used in many applications for the thermal recycling of the waste flue gas. Many of these boilers are designed as a horizontal type HRSG (see fig. 1). The evaporator of such a steam generator is characterized by an array of parallel tubes with different heat input. The paper presents the results of a theoretical stability analysis for a HRSG with a vertical tube bank. For the horizontal type HRSG the static instability, namely the reverse flow was analysed. The study was done at low system pressures and under hot start-up conditions for the boiler. The investigations show the influence of the geometry, the system pressure and the heat absorption of the individual tubes in the evaporator on the stability of the boiler. The aim of the study was to find design criteria to avoid reverse flow in the tubes of the evaporator. Addition of flow resistance at certain locations of the evaporator can improve the stability. A higher stability will be also achieved by the homogenization of the heat absorption in the individual layers of the bundle heating surface.

Research of Parameters’ Influence to the Reverse Flow of UTSG Under Natural Circulation

2013 ◽  
Author(s):  
Jun Duan ◽  
Tao Zhou ◽  
Zhong-yun Ju ◽  
Jing-jing Li ◽  
Ming-qiang Song ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Characteristic Length ◽  
Reverse Flow ◽  
Natural Circulation ◽  
Flow Distribution ◽  
Tube Diameter ◽  
Inlet Temperature ◽  
Medium Length ◽  
The Mathematical Model ◽  
Model Variation

The reverse flow will appear in some vertical UTSG’s U-tube under natural circulation. There is a characteristic length of U-tube when reverse flow appeared. Reverse flow has a bad effect on natural circulation of UTSG. By calculation of the mathematical model, variation of different parameters’ influence can be obtained. Studies have shown that reducing the diameter of the shortest U-tube, the medium length U-tube diameter is in constant, increasing the diameter of the longest U-tube and decrease the U-tube’s inlet temperature will improve the flow distribution of the U-tube, which can help preventing the occurrence of reverse flow.

Asymmetry Investigation on Single Phase Flow in Inverted U-Tubes of Steam Generator Under the Condition of Natural Circulation

2010 ◽  
Author(s):  
Chuan Wang ◽  
Lei Yu
Keyword(s):  
Experimental Data ◽  
Pressure Drop ◽  
Steam Generator ◽  
Mass Flux ◽  
Single Phase ◽  
Reverse Flow ◽  
Natural Circulation ◽  
Flow Characteristics ◽  
Operating Conditions ◽  
Outlet Temperature

In order to study the reverse flow characteristics in U-tubes of steam generator in the natural circulation case, the code RELAP5/MOD3.3 is used to model and calculate single-phase water flow for PWR under some typical operating conditions in the natural circulation case. The U-tubes of steam generator are classified according to their length and then are divided into different nodes and flow lines. The calculated results show that reverse flow exists in some inverted U-tubes of the steam generator, the natural circulation capacity of the primary coolant circuit system declines and the calculated net mass flux of the natural circulation accords with the experimental data. The traditional lumped parameter method can not simulate the reverse flow characteristics in inverted U-tubes and its result is much greater than the experimental data. When the steam generator outlet pressure is higher than inlet pressure, and gravitational pressure drop is lower than the total of frictional pressure drop and area change pressure drop, the reverse flow will occur. As to the nuclear power plant described in this paper, the mass flux of the shorter U-tubes drops more quickly and at last reverse flow will occur. The temperature distribution is uniform in inverted U-tubes, and it is almost identical with that of SG in secondary side. The occurrence of reverse flow can be judged by that whether the steam generator inlet temperature is lower than reactor outlet temperature obviously. It is indicated that reverse flow occurred in the U-tubes of the steam generator reduces the mass flux in the natural circulation system.

scholarly journals Effect of Heaving Movement on Flow Instability in U-Tubes of Marine Steam Generator under Natural Circulation

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Jianli Hao ◽  
Wenzhen Chen ◽  
De Zhang
Keyword(s):  
Steam Generator ◽  
Single Phase ◽  
Flow Instability ◽  
Reverse Flow ◽  
Natural Circulation ◽  
Critical Mass ◽  
Space Distribution ◽  
Tube Length ◽  
One Dimensional ◽  
Acceleration Amplitude

Under heaving movement conditions, the single phase flow instability in U-tubes is affected by the additional force, which will influence the marine reactor operation. In the present work, one-dimensional thermal-hydraulic model in U-tubes under heaving movement conditions is established, and the critical pressure drop (CPD) and critical mass flow rate (CMFR) which relate to the occurrence of reverse flow in U-tubes are proposed and analyzed. The effects of the heaving period and heaving acceleration amplitude on the flow instability in U-tubes with the different length are discussed. It is shown that (1) the CPD and CMFR are obviously affected by the heaving movement, which means that the reverse flow characteristic in U-tubes will be changed; (2) the fluctuation periods of the CPD and CMFR are the same as the heaving period, but the fluctuation magnitude of them is little affected by the heaving period; (3) the relative changes of CPD and CMFR are the linear function of heaving acceleration amplitude; and (4) the U-tube length has little influence on the relative changes of CPD and CMFR compared with the heaving acceleration amplitude, which means that the heaving movement has little influence on the space distribution of reverse flow in the U-tubes of marine steam generator.

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