In this study, experiments have been performed for an investigation on heat transfer of water in an inclined downward tube with an inner diameter of 20 mm and an inclined angle of 45° from the horizon, with the r...In this study, experiments have been performed for an investigation on heat transfer of water in an inclined downward tube with an inner diameter of 20 mm and an inclined angle of 45° from the horizon, with the range of pressure from 11.5 to 28 MPa, mass flux from 450 to 1550 kg/(m2 s), and heat flux from 50 to 585 k W/m2. Based on the experimental data, the temperature distribution in the tube wall was derived. The heat transfer characteristics of inclined downward flow were compared with that of vertical downward flow. The effects of heat flux on wall temperature were analyzed and the corresponding empirical correlations were presented. The results show that heat transfer characteristics of water in the inclined downward tube are not uniform along the circumference from the top surface to the bottom surface. An increase in heat flux exacerbates the non-uniformity. At subcritical pressures, both dry-out and departure from nucleate boiling(DNB) occur at the top surface of the inclined downward tube; inversely, only dry-out takes place on the bottom surface of the inclined downward tube and in the vertical downward tube. At near-critical pressures, DNB and dry-out occur in the comparing tubes with greater possibility. At supercritical pressures, heat transfer gets enhanced in the pseudo-critical enthalpy region; in the high enthalpy region, the top surface temperature of the inclined downward tube decreases obviously.展开更多
偏离泡核沸腾(DNB, Departure from Nucleate Boiling)设计准则用于确保在I、II类工况下,极限燃料棒表面不发生DNB。然而DNB设计准则考虑了95/95原则,因此即使验证了堆芯在特定工况下满足DNB设计准则,堆芯发生DNB燃料棒数量的期望值仍...偏离泡核沸腾(DNB, Departure from Nucleate Boiling)设计准则用于确保在I、II类工况下,极限燃料棒表面不发生DNB。然而DNB设计准则考虑了95/95原则,因此即使验证了堆芯在特定工况下满足DNB设计准则,堆芯发生DNB燃料棒数量的期望值仍然可能大于1根。为了验证满足DNB设计准则的I、II类工况下堆芯发生DNB燃料棒数量的期望值小于1根,一种全新的用于计算I、II类工况下堆芯发生DNB燃料棒数量的统计学方法被建立。CPR1000堆型的一种典型II类事故工况通过这种方法进行了分析。结果显示堆芯预计发生DNB燃料棒数量的期望值小于1,即从统计学角度认为在该工况下堆芯不会发生DNB。展开更多
建立了燃料棒轴向不同位置偏离泡核沸腾比(Departure from Nucleate Boiling Ratio,DNBR)的计算模型,研究分析了一回路冷却剂温度对DNBR的影响。针对超温、超功率ΔT保护触发安全级仪控系统执行紧急停堆功能,避免发生偏离泡核沸腾(DNB)...建立了燃料棒轴向不同位置偏离泡核沸腾比(Departure from Nucleate Boiling Ratio,DNBR)的计算模型,研究分析了一回路冷却剂温度对DNBR的影响。针对超温、超功率ΔT保护触发安全级仪控系统执行紧急停堆功能,避免发生偏离泡核沸腾(DNB)展开了研究。研究了安全级仪控系统的驱动信号、控制逻辑,明确了安全级仪控系统在避免反应堆偏离泡核沸腾的堆芯保护功能。为进一步分析事故工况下安全级仪控系统的保护作用奠定了基础。展开更多
在压水堆事故分析中,通常采用系统分析程序、热流密度计算程序和子通道分析程序分步计算堆芯偏离泡核沸腾比(Departure from Nucleate Boiling Ratio,DNBR)。利用该方法计算的堆芯DNBR结果准确性较好,但是计算过程繁琐、费时。对于系统...在压水堆事故分析中,通常采用系统分析程序、热流密度计算程序和子通道分析程序分步计算堆芯偏离泡核沸腾比(Departure from Nucleate Boiling Ratio,DNBR)。利用该方法计算的堆芯DNBR结果准确性较好,但是计算过程繁琐、费时。对于系统分析程序自带的堆芯DNBR简化计算模型,由于其根据堆芯限制线偏微分近似得到,适用范围较窄,准确性也难以保证。利用神经网络中的误差反向传播(Back Propagation,BP)算法,基于堆芯核功率、入口温度、流量和压力4个变量对应的一系列DNBR值,选取部分数据进行训练并建立模型,以达到快速和准确地预测堆芯DNBR的目的。根据误差分析,建立的计算模型具有较好的准确性,而且在部分失流事故和汽机停机事故下可较好地预测堆芯DNBR。展开更多
燃料组件边角栅元的阻力系数大于典型栅元和冷壁栅元。本文基于标准子通道模型,通过调整子通道模拟区域的位置,修改了通道、燃料棒以及格架阻力等相关参数,直接模拟燃料组件边角栅元的综合效应,进行偏离泡核沸腾比(Departure from Nucle...燃料组件边角栅元的阻力系数大于典型栅元和冷壁栅元。本文基于标准子通道模型,通过调整子通道模拟区域的位置,修改了通道、燃料棒以及格架阻力等相关参数,直接模拟燃料组件边角栅元的综合效应,进行偏离泡核沸腾比(Departure from Nuclear Boiling Ratio,简称DNBR)分析。分析结果表明:边角栅元的偏离泡核沸腾比能被典型和冷壁栅元的计算结果所包络。本文同时对燃料组件间隙和边角栅元的偏离泡核沸腾比的影响进行了进一步分析。展开更多
基金supported by the "Strategic Priority Research Program" Demonstration of Key Technologies for Clean and Efficient Utilization of Low-rank Coal (Grant No. XDA07030100)
文摘In this study, experiments have been performed for an investigation on heat transfer of water in an inclined downward tube with an inner diameter of 20 mm and an inclined angle of 45° from the horizon, with the range of pressure from 11.5 to 28 MPa, mass flux from 450 to 1550 kg/(m2 s), and heat flux from 50 to 585 k W/m2. Based on the experimental data, the temperature distribution in the tube wall was derived. The heat transfer characteristics of inclined downward flow were compared with that of vertical downward flow. The effects of heat flux on wall temperature were analyzed and the corresponding empirical correlations were presented. The results show that heat transfer characteristics of water in the inclined downward tube are not uniform along the circumference from the top surface to the bottom surface. An increase in heat flux exacerbates the non-uniformity. At subcritical pressures, both dry-out and departure from nucleate boiling(DNB) occur at the top surface of the inclined downward tube; inversely, only dry-out takes place on the bottom surface of the inclined downward tube and in the vertical downward tube. At near-critical pressures, DNB and dry-out occur in the comparing tubes with greater possibility. At supercritical pressures, heat transfer gets enhanced in the pseudo-critical enthalpy region; in the high enthalpy region, the top surface temperature of the inclined downward tube decreases obviously.
文摘偏离泡核沸腾(DNB, Departure from Nucleate Boiling)设计准则用于确保在I、II类工况下,极限燃料棒表面不发生DNB。然而DNB设计准则考虑了95/95原则,因此即使验证了堆芯在特定工况下满足DNB设计准则,堆芯发生DNB燃料棒数量的期望值仍然可能大于1根。为了验证满足DNB设计准则的I、II类工况下堆芯发生DNB燃料棒数量的期望值小于1根,一种全新的用于计算I、II类工况下堆芯发生DNB燃料棒数量的统计学方法被建立。CPR1000堆型的一种典型II类事故工况通过这种方法进行了分析。结果显示堆芯预计发生DNB燃料棒数量的期望值小于1,即从统计学角度认为在该工况下堆芯不会发生DNB。
文摘建立了燃料棒轴向不同位置偏离泡核沸腾比(Departure from Nucleate Boiling Ratio,DNBR)的计算模型,研究分析了一回路冷却剂温度对DNBR的影响。针对超温、超功率ΔT保护触发安全级仪控系统执行紧急停堆功能,避免发生偏离泡核沸腾(DNB)展开了研究。研究了安全级仪控系统的驱动信号、控制逻辑,明确了安全级仪控系统在避免反应堆偏离泡核沸腾的堆芯保护功能。为进一步分析事故工况下安全级仪控系统的保护作用奠定了基础。
文摘燃料组件边角栅元的阻力系数大于典型栅元和冷壁栅元。本文基于标准子通道模型,通过调整子通道模拟区域的位置,修改了通道、燃料棒以及格架阻力等相关参数,直接模拟燃料组件边角栅元的综合效应,进行偏离泡核沸腾比(Departure from Nuclear Boiling Ratio,简称DNBR)分析。分析结果表明:边角栅元的偏离泡核沸腾比能被典型和冷壁栅元的计算结果所包络。本文同时对燃料组件间隙和边角栅元的偏离泡核沸腾比的影响进行了进一步分析。
