Effects of Rolling on Characteristics of System Under Forced Circulation and Natural Circulation

2021 ◽  
Author(s):  
RONG CAI ◽  
Lili Liu ◽  
Hongyu Fang ◽  
Baowen Chen ◽  
Zehua Ma
Keyword(s):  
Natural Circulation ◽  
Forced Circulation

Optimization of forced circulation to natural circulation transition characteristics of IPWR

2021 ◽  
Vol 157 ◽  
pp. 108249
Author(s):  
Yifan Xu ◽  
Minjun Peng ◽  
Genglei Xia ◽  
He Shang
Keyword(s):  
Natural Circulation ◽  
Forced Circulation

scholarly journals Gas Turbine Heat Recovery Steam Generators for Combined Cycles Natural or Forced Circulation Considerations

1988 ◽  
Author(s):  
Akber Pasha
Keyword(s):  
Gas Turbine ◽  
Steam Generator ◽  
Heat Recovery ◽  
Power Plants ◽  
Natural Circulation ◽  
Combined Cycle ◽  
Heat Recovery Steam Generator ◽  
Steam Generators ◽  
Forced Circulation ◽  
Gas Turbine Exhaust

In recent years the combined cycle has become a very attractive power plant arrangement because of its high cycle efficiency, short order-to-on-line time and flexibility in the sizing when compared to conventional steam power plants. However, optimization of the cycle and selection of combined cycle equipment has become more complex because the three major components, Gas Turbine, Heat Recovery Steam Generator and Steam Turbine, are often designed and built by different manufacturers. Heat Recovery Steam Generators are classified into two major categories — 1) Natural Circulation and 2) Forced Circulation. Both circulation designs have certain advantages, disadvantages and limitations. This paper analyzes various factors including; availability, start-up, gas turbine exhaust conditions, reliability, space requirements, etc., which are affected by the type of circulation and which in turn affect the design, price and performance of the Heat Recovery Steam Generator. Modern trends around the world are discussed and conclusions are drawn as to the best type of circulation for a Heat Recovery Steam Generator for combined cycle application.

Analysis and Research on Natural Circulation Capacity of HFETR

2016 ◽  
Author(s):  
Taozhong Xu ◽  
Caiyu Deng ◽  
Yuxin Xiang
Keyword(s):  
Pressure Vessel ◽  
Cold Water ◽  
Flow Direction ◽  
Natural Circulation ◽  
Reactor Power ◽  
Hot Water ◽  
Forced Circulation ◽  
The Core ◽  
Establishment Process ◽  
Residual Heat

Natural circulation is being used as an important circulation to remove reactor residual heat. In the core of High Flux Engineering Trial Reactor of China (HFETR), the coolant is driven by pumps normally and flows from upside to downside in the core. When HFETR is shut down or runs in low power, the natural circulation between the hot water in the core and the cold water in the reflector inside the pressure vessel is established to cool down the core. Since the natural circulation processed only in the pressure vessel, the accident pumps need to be turned on periodically to remove reactor residual heat. The inversion of flow direction in HFETR and internal natural circulation lead to a different natural circulation establishment process from traditional reactor in which coolant flows form down to top normally. In this paper the transition between the natural circulation and forced circulation is analyzed by RELAP5/MOD3 code. The results showed that the accident pump could be turned off in the power of 850kW; The time, at which the accident pump needs to be turned on to transit the natural circulation to forced circulation, is decided by the temperature of the water in top of pressure vessel, and a formula between temperature of the water in the top of pressure vessel and the reactor power was obtained. The research results have theoretical and practical value to the full use of the natural circulation ability, as well as the safety of the engineering reactors or similar test facilities.

Effects of Rolling on Characteristics of System Under Forced Circulation and Natural Circulation

2020 ◽  
Author(s):  
Rong Cai ◽  
Nina Yue ◽  
Hongyu Fang ◽  
Baowen Chen ◽  
Lili Liu ◽  
...  
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Nuclear Power ◽  
Nuclear Reactor ◽  
Natural Circulation ◽  
Thermal Parameters ◽  
Reactor System ◽  
Hydraulic Characteristics ◽  
Forced Circulation ◽  
Rolling Condition

Abstract The marine nuclear power plant operating in the marine environment has complicated motion under the influence of wind and waves. The movement of marine nuclear power plant will affect the thermal-hydraulic characteristics of its nuclear reactor system. Compared with other typical motion conditions, the effects of rolling conditions on the thermal-hydraulic characteristics of the nuclear reactor system are the most complex. In order to study the effects of rolling conditions on the thermal-hydraulic characteristics of the nuclear reactor system, a thermal-hydraulic system code for motion conditions named STAC was developed. The STAC code was verified by the experiments conducted in Japan. The effects of rolling conditions on the thermal-hydraulic characteristics of the nuclear reactor system under forced circulation and natural circulation are studied with the STAC code. The simulation results show that the thermal parameters of the reactor system under rolling condition fluctuate periodically. The fluctuation period of the thermal parameters of the core is half of the rolling period, and the fluctuation periods of other thermal parameters are the same as the rolling period. The effect of rolling condition on thermal-hydraulic parameters under forced circulation is smaller than that under natural circulation. The fluctuation amplitudes of the thermal parameters increase with the angle amplitude of the rolling condition. There is a rolling period with the smallest fluctuation amplitude. Under the rolling condition with short period, the fluctuation amplitudes of the thermal parameters increase and their average values change rapidly as the rolling period decreases. Under the rolling condition with large period, the fluctuation amplitudes of the thermal parameters increase with the rolling period, and they tend to fixed values.

Research of efficiency of solar coating in the heat supply system

2021 ◽  
Author(s):  
Stepan Shapoval ◽  
Nadiia Spodyniuk ◽  
Oleksandra Datsko ◽  
Pavlo Shapoval
Keyword(s):  
Development Strategy ◽  
Heat Supply ◽  
Natural Circulation ◽  
Thermal Characteristics ◽  
Heat Supply System ◽  
Physical Parameters ◽  
Forced Circulation ◽  
Average Value ◽  
Energy Efficient Buildings ◽  
Carrier Energy

AbstractAccording to the energy development strategy of Ukraine, implementation of energy efficient buildings is needed, in which external protections are converters of solar energy into heat. The article presents studies of solar coating with direct coolant supply. Studies of the average value of the heat loss coefficient of the solar coating were also carried out. As a result, the efficiency of the solar coating under the mode of forced circulation of the coolant is 0.67, at natural circulation of the coolant – 0.57 and at its direct supply is 0.71. Experimental researches of thermal and physical parameters of a solar covering and system of heat supply on its basis showed in the corresponding dependences influence on its thermal characteristics of dynamic modes of the heat carrier, energy, kinetic characteristics of the environment.

Process Design of Heat Pump Evaporation Technology for Liquid Radioactive Waste Treatment

2017 ◽  
Author(s):  
Jia Lu ◽  
Yan Zhou
Keyword(s):  
Radioactive Waste ◽  
Heat Pump ◽  
Waste Treatment ◽  
Natural Circulation ◽  
Liquid Radioactive Waste ◽  
Evaporation Process ◽  
High Concentration ◽  
Separation Function ◽  
Forced Circulation ◽  
Circulation Evaporator

The Site Radwaste Treatment Facility (SRTF) was to treat the liquid radioactive waste with high concentration of electrolytes in CAP1400 plant. Unlike the forced-circulation or natural-circulation evaporator, the waste was purified by evaporation process using heat pump principle in SRTF. This process combined the benefits of heat pump technology and the separation function of evaporation. This paper gave a brief description of the complete evaporation process. The main equipments of the process included pre-heater, evaporator, demister, steam compressor, and distillate tank. The whole system and each unit operation in the process were elaborately simulated based on energy balance. The results can be further used for equipments selection and design. Through the whole discussion of the heat pump evaporation process, it showed the heat pump evaporation process has remarkable energy efficiency and great advantages in equipment layout compared to traditional evaporation treatment for liquid radioactive waste.

Coupled Simulations of Natural and Forced Circulation Tests in NACIE Facility Using RELAP5 and ANSYS Fluent Codes

2014 ◽  
Author(s):  
D. Martelli ◽  
N. Forgione ◽  
G. Barone ◽  
A. Del Nevo ◽  
I. Di Piazza ◽  
...  
Keyword(s):  
Natural Circulation ◽  
Experimental Tests ◽  
Research Centre ◽  
Assisted Circulation ◽  
Coupling Scheme ◽  
Ansys Fluent ◽  
Forced Circulation ◽  
Model Set ◽  
Set Up ◽  
2D And 3D

In this work the activity performed at the DICI (Dipartimento di Ingegneria Civile e Industriale) of the Pisa University in collaboration with the ENEA Brasimone Research Centre is presented. In particular the document deals with the application of an in-house developed coupling methodology between a modified version of RELAP5/Mod3.3 and Fluent commercial CFD code, to the NACIE (Natural Circulation Experiment) LBE experimental loop (built and located at the ENEA Brasimone research centre). The first part of the document treats the description of the NACIE loop type facility, while in the second part, the developed coupling tool is presented and the obtained numerical results are compared to stand alone RELAP5 results and to data obtained from the NACIE experimental campaign. The experimental tests are performed varying the argon flow rate and the electric power supplied to the heater and both natural and assisted circulation tests are investigated. The numerical model set-up is based on a two-way explicit coupling scheme and 2D and 3D geometrical domain were investigated. Comparative analyses among numerical and experimental results showed good agreement, giving positive feedback on the feasibility and capability of the developed coupling methodology.

Calculation Study on Onset of Nucleate Boiling of Natural Circulation Based on Density Gradient

2012 ◽  
Author(s):  
Sheng Cheng ◽  
Tao Zhou ◽  
Lei Zhang ◽  
Yanping Huang
Keyword(s):  
Density Gradient ◽  
Natural Circulation ◽  
Flow Characteristics ◽  
Circulation Model ◽  
Nucleate Boiling ◽  
Gradient Theory ◽  
Forced Circulation ◽  
Characteristic Factor ◽  
Calculation Results ◽  
Heated Fluid

The flow characteristics of natural circulation are relying on the heated fluid density difference as a driving force. Based on density gradient theory, a characteristic factor of natural circulation was proposed. The forced circulation models of Onset of Nucleate Boiling (ONB) of Bergles&Rohsenow and SU Shunyu were modified through the characteristic factor. The calculation results showed that the modified forced circulation models could calculate the occurrence of ONB in the condition of natural circulation better. Meanwhile, the calculating results and differences of heat flux at ONB between the models of natural and forced circulation were given by changing the thermal parameters. The results revealed that, most of the calculated values of natural circulation model were lower than those of forced circulation models when inlet subcooling and pressure varied, which meant the occurrence of ONB in natural circulation preceded that in forced circulation. The calculated results of forced circulation models could close to those of the natural circulation model through modification, which indicated the characteristic factor of natural circulation proposed in this paper was one of the respects which could reflect the inherent mechanistic difference between natural and forced circulation.

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