Severe accident analysis is important for the safety evaluation of a nuclear power plant (NPP). In this paper, analysis has been performed for a Chinese three-loop Pressurized Water Reactor (PWR) severe accident induc...
Severe accident analysis is important for the safety evaluation of a nuclear power plant (NPP). In this paper, analysis has been performed for a Chinese three-loop Pressurized Water Reactor (PWR) severe accident induced by loss of coolant accident (LOCA) along with Station- Block-Out (SBO) using the MIDAC code. The simulation results show the influence of different break sizes in the cold leg on the severe accident progression. Important parameters, such as primary coolant system (RCS) pressure, core melting time, pressure vessel rupture time. are analyzed with three different break sizes in the cold leg. With the break size of 0.002 m 2 , the reactor core starts to melt at 1481 s and the lower head fails at 10,317 s after the accident occurs. With a larger break size of 0.05 m 2 , the reactor core starts to melt at 1066 s and the lower head fails at 2473 s. If the break size is further enlarged to 0.2 m 2 , the reactor core starts to melt at 422 s and the lower head fails at 1757 s. Another case in which a hot leg break is with the size of 0.002 m 2 is performed. The reactor core starts to melt at 3641 s and the lower head fails at 14,744 s. It is less severe than the cold leg break accident. The severe accident prevention and mitigation measures are summarized based on the computation results. The results are helpful to develop the management strategies and guideline for the severe accident of the similar types of PWRs.
This paper provides a comprehensive analysis on cooling tower fouling data taken from seven 15.54 mm I.D. helically ribbed, copper tubes and a plain tube at Re = 16000. There are two key processes during fouling forma...
详细信息
This paper provides a comprehensive analysis on cooling tower fouling data taken from seven 15.54 mm I.D. helically ribbed, copper tubes and a plain tube at Re = 16000. There are two key processes during fouling formation： fouling deposition and fouling removal, which can be determined by mass transfer and fluid friction respectively. The mass transfer coefficient can be calculated through three analogies： Prandtl analogy, VonKarman analogy, and Chilton-Colburn analogy. Based on our analyses, Von-Karman analogy is the optimized analogy, which can well predict the formation of cooling tower fouling. Series of semi-theoretical fouling correlations as a function of the product of area indexes and efficiency indexes were developed, which can be applicable to different internally ribbed geometries. The correlations can be directly used to assess the fouling ootential of enhanced tubes in actual coolinu tower water situations.
Generally, the Offset Strip Fin (OSF) in a plate-fin heat exchanger provides a greater heat transfer coefficient than plain plate-fin, but it also leads to an increase in flow friction. A new parameter, called relativ...
详细信息
Generally, the Offset Strip Fin (OSF) in a plate-fin heat exchanger provides a greater heat transfer coefficient than plain plate-fin, but it also leads to an increase in flow friction. A new parameter, called relative entropy generation distribution factor, Ψ * , is proposed to evaluate the thermodynamic advantages of OSFs. This parameter presents a ratio of relative changes of entropy generation. The relative effects of the geometrical parameters α, γ and δ are discussed. The results show that there exist the optimum values of α and γ at a certain flow condition, which obviously maximize the degree of the heat transfer enhancement of OSFs.
Solar receiver reactor is the key component of supercritical water gasification of biomass using concentrating solar energy, and itsthermal performance directly affects the thermal efficiency and biomass gasification ...
详细信息
Solar receiver reactor is the key component of supercritical water gasification of biomass using concentrating solar energy, and itsthermal performance directly affects the thermal efficiency and biomass gasification results. The temperature distributions of solar receiver reactor and reactant fluid are *** results showed that direct normal solar irradiation (DNI) have prominent effect on the temperature of cavity type solar receiver reactor, thus affecting the SCWG reaction behaviors and gasification results. A series of on-sun experiments were carried out,temperature is relatively stable withDNI small fluctuations, and the nominal fluid temperatures at the outlet of reactor varied in the range 500–650 o C, which could completely meet the need of the temperature for biomass gasification in supercritical *** compounds of biomass (ethylene glycol, ethanol,glycerin and glucose) were continuously gasified under SCW conditions to generate hydrogen-rich fuel gas in the apparatus. Gas yields, carbon gasification efficiency and the total gasification efficiency increase with increasing DNI. The range of GE and CE is 48.5-105.8%, 37.5-95.6%, *** thermal performance and gasification results show thatsolar receiver/reactor used in this study is one of the good configurations that can be used for SCWG of biomass using concentrating solar energy.
The continuous steam region generated by high-speed steam jet discharging into subcooled water is called the steam plume. The plume penetration length is an important index for heat exchange capability of steam jet. I...
详细信息
When a coal-fired unit operates at a partial load, the decrease at regenerative steam pressure leads to a decrease in boiler feedwater temperature, affecting not only the thermal economical efficiency, but also the se...
详细信息
When a coal-fired unit operates at a partial load, the decrease at regenerative steam pressure leads to a decrease in boiler feedwater temperature, affecting not only the thermal economical efficiency, but also the selective catalytic reduction (SCR) denitrification effect and the boiler combustion stability. A feedwater system with the thermal vapor compressor has been studied in the present paper. The high pressure regenerative steam is injected by the live steam to heat boiler feedwater to increase its temperature. Mathematical models of the thermal vapor compressor, boiler and turbine regenerative system are established to calculate the performance of a 660MW supercritical air cooling unit at a 60% load. It was found that although the energy-saving effect is small, it is positive to improve the SCR denitrification effect and stabilize the boiler combustion.
In order to improve the energy utilization efficiency of thermal power plants and to solve the heating shortage problem in China, the absorption heat pump is usually employed to recover the heat of turbine exhaust ste...
详细信息
In order to improve the energy utilization efficiency of thermal power plants and to solve the heating shortage problem in China, the absorption heat pump is usually employed to recover the heat of turbine exhaust steam for heating supply. In the existing references, few researchers considered the heating load characteristics when designing the recovery system. In this paper, the design thought of heat recovery system of turbine exhaust steam using absorption heat pump for heating supply based on heating load characteristics was presented. With an engineering case, the heat recovery system was designed and its economic efficiency was calculated.
The ANSYS FLUENT14.5 was employed to simulate the two-phase forced convection subcooled boiling in a vertical heated pipe. Different turbulence models, wall functions and two-phase turbulence treatments were utilized ...
详细信息
暂无评论