Analysis on static heat transfer characteristics of U-tube natural circulation steam generator

2013 ◽  
Author(s):  
Li Wang ◽  
Bin Ge ◽  
Junli Zhang
Keyword(s):  
Heat Transfer ◽  
Steam Generator ◽  
Natural Circulation ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics

scholarly journals Numerical study on heat transfer characteristics of nanofluid based natural circulation loop

2018 ◽  
Vol 22 (2) ◽  
pp. 885-897 ◽  
Author(s):  
Ramesh Bejjam ◽  
Kiran Kumar
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Natural Circulation ◽  
Flow Behavior ◽  
Circulation Loop ◽  
Heat Transfer Characteristics ◽  
Step Size ◽  
Particle Volume ◽  
Transfer Characteristics ◽  
Natural Circulation Loop

In this paper the steady-state analysis has been carried out on single phase natural circulation loop with water and water based Al2O3 (Al2O3-water) nanofluid at 1%, 3%, 5%, and 6% particle volume concentrations. For this study, a 3-D geometry of natural circulation loop is developed and simulated by using the software, ANSYS (FLUENT) 14.5. Based on the Stokes number, mixture model is adopted to simulate the nanofluid based natural circulation loop. For the simulations, the imposed thermal boundary conditions are: constant heat input over the range of 200-1000 W with step size of 200 W at the heat source and isothermal wall temperature of 293 K at the heat sink. Adiabatic boundary condition is imposed to the riser and down-comer. The heat transfer characteristics and fluid-flow behavior of the loop fluid in natural circulation loop for different heat inputs and particle concentrations are presented. The result shows that the mass-flow rate of loop fluid in natural circulation loop is enhanced by 26% and effectiveness of the natural circulation loop is improved by 15% with Al2O3-water nanofluid when compared with water. All the simulation results are validated with the open literature in terms of Reynolds number and modified Grashof number. These comparisons confidently say that the present 3-D numerical model could be useful to estimate the performance of natural circulation loop.

Modeling of the Supercritical Steam Generator of MHTGR in Engineering Simulator

2014 ◽  
Author(s):  
Dan Liu ◽  
Jun Sun ◽  
Zhe Sui ◽  
Chun-lin Wei ◽  
Yu-liang Sun
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Steam Generator ◽  
Supercritical Water ◽  
Heat Transfer Characteristics ◽  
Coupling Effects ◽  
Transfer Characteristics ◽  
Helical Tubes ◽  
Steam Generator Model ◽  
High Temperature Gas

The Modular High Temperature Gas-cooled Reactor (MHTGR) could realize higher efficiency and lower costs by developing the multi-modular high temperature gas-cooled reactors combined with supercritical steam turbine unit. The coupling effects among different modules are crucial to the designs and operation analyses of the multi-modular reactors. By establishing the engineering simulator for multi-modular reactors, the coupling effects can be studied and optimized to advance the reactor designs, due to the advantages of real-time calculations and coupled calculations. As key energy transfer equipment, the steam generator is very important to the reactor operation, and focused in the modeling of the engineering simulator system for multi-modular reactors. In this paper, the once-through steam generator consisted of helical coils was modeled and optimized in the vPower integrated simulation platform. From the detailed analyses of the distributions of temperatures, heat flux, and other parameters along the heat transfer tubes, it showed that the steam generator model well presented the supercritical water properties and heat transfer characteristics inside helical tubes. Also, the heat transfer correlations of the supercritical water inside helical tubes were investigated, discussed and also compared to test the uncertainty and influence to the whole steam generator model. And the results indicated that most heat transfer correlations showed similar results and had little effect on the primary side in the steady state operation condition. In future work, the model and heat transfer characteristics of the supercritical steam generator will be further tested in more transients and integrated into complete engineering simulator for multi-module reactors.

Investigation on Heat Transfer Characteristics in the Test Section With Non-Uniform Heat Flux Distribution Under Natural Circulation

2017 ◽  
Author(s):  
Qiang Wang ◽  
Puzhen Gao ◽  
Xianbing Chen ◽  
Zhongyi Wang ◽  
Ying Huang
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Test Section ◽  
Flux Distribution ◽  
Natural Circulation ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics

Natural circulation served as an indispensable part of nuclear, attracted much more attentions in recent years. It does not need a pump to provide power. The operating principle of natural circulation caused its complexity in analysis process. It was still a difficult issue to reveal the law of natural circulation accurately. Many experiments and calculations had to be conducted to study the basic physical regulation. This paper concentrated upon the heat transfer characteristics in the test section with two different types of heat flux distribution. The two types of heating flux distribution in the test section were linear and chopped cosine along axial direction. Based on a natural circulation experimental facility, physical models and mathematic models were established. RELAP5 code was used to calculate the thermal hydraulic state of natural circulation loop. The variation of heat transfer coefficient along flow direction was different. It was tightly related to heat flux. Some relevant experiments were conducted in many different conditions and steady sate experimental data were achieved to verified theoretical calculations. Experimental data, such as water temperature, wall temperature and flow rate were recorded when the system is stable. The heat transfer coefficients were calculated according to the experimental data. The factors that affected the heat transfer characteristics of natural circulation were analyzed by comparing the heat transfer coefficient under different conditions. The heat transfer coefficient was calculated according to the empirical correlations as well. After a series of analysis, the results indicated heat transfer coefficient had an obvious difference, which influenced ability of natural circulation. Comparing with experimental data, the evaluation of different empirical correlations was conducted in two test sections. Some empirical correlations turned out to be suitable for the estimation of heat transfer in experiment facility. The increase of heat flux could enhance heat transfer process in the two test section under low pressure. Average heat transfer coefficient increased with the decrease of inlet subcooling degree. The system pressure effected the heat transfer characteristics of natural circulation as well. The increase of mass flux would promote heat transfer while the level was different. RELAP5 had a great agreement with experimental data in single phase flow. Natural circulation ability was influenced by the position of average heat source center, which was slightly different in the research objects. The research would lend strong empirical support to the guideline of experiment and subsequence study in natural circulation.

Study on Flow and Heat Transfer Characteristics of Different States of Water Under Natural Circulation

2014 ◽  
Author(s):  
Zhongyun Ju ◽  
Tao Zhou ◽  
Jingjing Li ◽  
Zejun Xiao
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flow ◽  
Supercritical Water ◽  
Natural Circulation ◽  
Heat Transfer Characteristics ◽  
Two Phase ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer

Software CFX is used to build a typical natural circulation loop to study flow and heat transfer characteristics of water vapor, the vapor-liquid two-phase and supercritical water under natural circulation. During the process of natural circulation, the variation of parameters, heat transfer coefficient and mass flow is compared. It is found that when formed a natural circulation, the steam has a lower mass flow and heat transfer coefficient, while the two parameters of two-phase and supercritical water are higher. Indicates that the heat transfer capability of steam is weak, the steam cannot transfer heat out opportunely when serious accidents take place. The two-phase water is of high heat transfer coefficient. Supercritical water is of strong exchange capacity, supercritical water under natural circulation is a promising flow pattern.

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