共查询到17条相似文献,搜索用时 46 毫秒
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本文分析了定位格架对临界热流密度(CHF)影响的机理,讨论了如何判断定位格架热工性能的好坏;对我院已做过的几种带不同定位格架的核电站燃料棒束的 CHF 实验结果作了对比分析,并与国外最新的 CHF 经验公式作了对比。 相似文献
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本文分别从两种不同类型的临界热流密度(CHF)的触发机理出发,分析了内棒偏心和弯曲对CHF的影响。以氟利昂(R-134a)作为流动工质,在竖直向上流动的环形通道内开展了仅内棒加热的CHF实验研究。实验段包含3种形式:同心、偏心和弯曲。偏心实验结果表明:在高过冷工况下,内棒偏心将对CHF造成惩罚,且偏心率为0783的实验段对CHF惩罚更严重;在低过冷工况下,偏心效应减弱。高压高质量流速工况,空泡漂移效应会导致偏心率为0783的CHF大于偏心率为0435的CHF。弯曲实验结果表明:小闭合度的弯曲对CHF几乎没有影响。大闭合度的弯曲对于低质量流速的Dryout型CHF,弯曲棒会破坏液膜的稳定性;对于低质量流速的DNB型CHF,空泡漂移效应远小于偏心通道,弯曲的CHF小于相同最小间隙下偏心的CHF。 相似文献
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在空泡物理和自然循环重点实验室氟里昂热工实验装置上进行了CHF实验 ,实验段为9 5×1 0mm元件管组成的 4× 4棒束 ,并对其开展了 4× 4棒束CHF流体模化研究。在压力 1 5 9~ 2 73MPa、质量流速 4 88~ 2 0 80kg (m2 ·s)、临界含汽率 -0 2 0~ 0 3 0的工况范围内 ,采集了 1 70个 4× 4棒束CHF实验数据 ,并与压力 9 9~ 1 6 2MPa、质量流速 2 74~ 1 4 73kg (m2 ·s)、临界含汽率 -0 2 0~0 3 4工况范围内 ,以水为工质相同棒束实验段内的 2 0 6个棒束CHF实验数据进行比较 ,发现Ahmad补偿失真模型、张振杰模型和Stevens Kirby模型在上述工况范围内不再适用于棒束CHF的模化 ,这些模型的预测偏差均大于 2 0 %以上 ,而且棒束CHF模化的流量模化因子k明显地受压力、质量流量和入口含汽率的影响。据此提出适用于上述工况范围内 4× 4棒束CHF模化的流量模化因子k的关系式 ,其CHF预测偏差在± 1 5 %以内 ,均方根误差为 7 0 5 %。 相似文献
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采用R134a作为流体工质,对单棒垂直方形通道临界热流密度(CHF)进行了实验研究。流道横截面为19 mm×19 mm的方形通道,内置外径为9.5 mm的单根加热棒,用来模拟压水堆中典型栅元通道。实验工况通过流体模化方法覆盖了压水堆典型运行工况。实验结果表明,R134a在方形通道内的CHF参数趋势与圆管中水的CHF参数趋势相同,R134a可以替代水作为模化工质;通过对圆管Bowring关系式和Katto & Ohno关系式进行冷壁因子修正,可用于预测带有冷壁的方形通道的CHF;Katto的流体模化方法适用于带有冷壁的方形通道。 相似文献
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测定了半圆形通道内六根均匀加热元件的临界热流密度。采用“硅光电池”法进行临界监测。给出了加热段出口附近装有定位栅和整个加热段都不装定位栅(“光棒”)两种情况的实验结果,并将结果分别整理成两个经验公式。实验结果表明:此种结构定位栅使临界热流密度严重降低。 相似文献
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为研究核反应堆中定位格架及搅混翼对沸腾临界现象产生的影响,本文采用计算流体动力学(CFD)分析方法,探讨了棒束通道中定位格架的数目、位置和搅混翼的角度对于沸腾临界现象的影响。结果表明:定位格架会对主流流动产生阻力,同时定位格架数目越多,沸腾临界发生的温度也越高,但将定位格架布置在沸腾临界发生位置时,则可有效改善壁面传热环境并降低沸腾临界发生时的峰值温度。搅混翼的存在则会有效降低加热面附近空泡份额,改善传热环境,但搅混翼角度过大时会导致沸腾临界提前发生。 相似文献
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自然循环条件下,矩形通道内的临界热流密度(CHF)发生受到很多因素影响,目前对其特征的把握尚不完善。将本研究中得到的实验结果与Katto的强迫循环和Zhang的自然循环两种CHF模型的计算值进行比较,分析两种模型在实验条件下的适用性以及入口流速、出口质量含汽率和压力对CHF的影响。研究表明:Katto模型的计算结果普遍高于实验值,而Zhang模型的计算结果与实验值符合较好。随着入口流速的增大,自然循环和强迫循环CHF均逐渐增大;随着出口质量含汽率的增大,两类循环的CHF均减小;随着压力的增大,两类循环的CHF都增大,而在较大压力条件下自然循环CHF的增长速率随系统压力的增大而减小。 相似文献
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《Journal of Nuclear Science and Technology》2013,50(9):1189-1198
In the development of supercritical pressure water cooled reactors, it is important to understand the characteristics of a heat transfer near the thermodynamic critical point. An experimental study on the critical heat flux near the critical pressure has been performed with a 5 × 5 square array heater rod bundle cooled by R-134a fluid (P c = 4:059MPa, T c = 101°C). The critical power has been accurately measured up to the reduced pressure of 0.99 (4.03 MPa). The critical power decreases sharply at a pressure of about 3.8–3.9 MPa as the pressure approaches the critical pressure. For the low mass fluxes of 50 to 250kg/m2, a sharp decrease in the critical power is not observed near the critical pressure. The CHF phenomenon near the critical pressure no longer leads to an inordinate increase in the heated wall temperature such as the case of DNB at normal pressure conditions. In the pressure region close to the critical pressure, there is a threshold pressure at which the CHF phenomenon disappears. When the pressure exceeds the threshold pressure, the wall temperature increases monotonously without a CHF occurrence according to the power level applied to the heater rods. The threshold pressure moves toward the lower pressure region gradually with an increasing mass flux. 相似文献
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铅铋冷却快堆作为第4代反应堆候选之一具有安全性高等特点,研究其在正常工况下的热工水力特性具有重要意义。本文基于商用计算流体力学(CFD)软件STAR-CCM+,使用流固耦合的方法对带有绕丝结构的19棒束铅铋组件进行数值分析,探究了质量流量、功率等边界条件对组件内部流动传热特性的影响。模拟计算结果表明:CFD方法在子通道中心温度和壁面温度预测上与实验结果取得了较好的一致。同时,绕丝结构的存在使得子通道之间存在周期性的横向交混,并使得棒束表面温度呈现震荡。随质量流量的增加,子通道间横向交混增大。功率变化对通道间的横向交混速度的影响较小,冷却剂温度的横向分布无明显差异。 相似文献
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《Journal of Nuclear Science and Technology》2013,50(2):207-209
The authors have developed a new on-line corrosion product monitor (OCPM) to automatically measure the concentrations of corrosion products in PWR secondary water. The corrosion products of interest for this application are mainly iron and copper. The OCPM offers a number of outstanding features: (1) it measures trace metals on-line; (2) it allows simultaneous quantitative multi-element analysis; (3) its operation is fully automatic with an excellent lower detection limit; and (4) it is transportable and easy to operate. During its development stage, the OCPM was applied at an actual PWR plant and was able to successfully automatically analyze the concentrations of iron and other trace metals contained in the PWR secondary water, while maintaining operational stability without operator intervention for long periods of time. It was also shown that the use of this new system would greatly reduce the workload of plant water chemistry personnel, providing a better alternative to conventional chemical analysis methods. The OCPM is now being introduced into several PWR plants in Japan, with the objectives of conducting detailed studies of the corrosion product behavior in the plant systems and reducing the workload of plant personnel. 相似文献
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为对过冷沸腾两相流动进行准确模拟,并探索临界热流密度(CHF)预测方法,本文基于共轭传热和两相CFD分析的方法,通过流固界面耦合,建立流固共轭传热两相流动耦合求解的数值模型。首先通过典型燃料棒栅元过冷沸腾两相流动的模拟,验证数值模型的正确性。随后对燃料子通道内两相流动进行模拟,并在两相流动模拟的基础上,通过准瞬态的方法,建立与CHF试验过程非常近似的CHF预测方法,将加热壁面的温度飞升作为CHF判定的标准,实现对燃料组件子通道CHF的数值预测。研究表明,本文建立的数值模拟方法,可为燃料组件或其他换热系统的CHF预测奠定基础,为燃料组件的设计提供新的辅助手段。 相似文献
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《等离子体科学和技术》2016,18(2):190-196
An accurate critical heat flux(CHF) prediction method is the key factor for realizing the steady-state operation of a water-cooled divertor that works under one-sided high heating flux conditions.An improved CHF prediction method based on Euler's homogeneous model for flow boiling combined with realizable k-ε model for single-phase flow is adopted in this paper in which time relaxation coefficients are corrected by the Hertz-Knudsen formula in order to improve the calculation accuracy of vapor-liquid conversion efficiency under high heating flux conditions.Moreover,local large differences of liquid physical properties due to the extreme nonuniform heating flux on cooling wall along the circumference direction are revised by formula IAPWSIF97.Therefore,this method can improve the calculation accuracy of heat and mass transfer between liquid phase and vapor phase in a CHF prediction simulation of water-cooled divertors under the one-sided high heating condition.An experimental example is simulated based on the improved and the uncorrected methods.The simulation results,such as temperature,void fraction and heat transfer coefficient,are analyzed to achieve the CHF prediction.The results show that the maximum error of CHF based on the improved method is 23.7%,while that of CHF based on uncorrected method is up to 188%,as compared with the experiment results of Ref.[12].Finally,this method is verified by comparison with the experimental data obtained by International Thermonuclear Experimental Reactor(ITER),with a maximum error of 6% only.This method provides an efficient tool for the CHF prediction of water-cooled divertors. 相似文献