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自然循环蒸汽发生器并联倒U型管流量分配计算 总被引:3,自引:3,他引:0
针对自然循环工况下蒸汽发生器部分倒U型管内存在倒流现象,通过对倒U型管内流动传热特性进行分析,获得了倒流发生的判断依据,从而编制了流量分配计算程序。采用该程序对某型蒸汽发生器并联倒U型管流量分配进行了计算,通过将结果与实验值进行对比分析,对程序可信度进行了验证,并采用该程序对蒸汽发生器并联倒U型管主要热工参数随进出口压降变化情况进行了计算分析。结果表明,倒流现象发生在短管内,倒流的发生使得蒸汽发生器一次侧净流量和单位时间输热呈阶梯下降,对反应堆安全产生较大的影响。 相似文献
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针对立式倒U型管自然循环蒸汽发生器传热管内的两相倒流现象,基于均相流模型,建立了U型管内低含气率两相流动传热理论模型,给出了U型管的进出口压降-质量流量曲线,分析了U型管内出现两相倒流现象的机理,研究了二次侧流体温度和入口含气率对倒流现象的影响规律,并与单相倒流进行了对比。利用RELAP5/MOD 3.3程序对相同条件下的倒流问题进行了计算。研究表明,提高蒸汽发生器二次侧工作压力可减少倒流,两相流入口含气率越高,倒流越易发生,两相流较单相流在U型管内更易倒流。 相似文献
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以欧洲压水堆热工实验装置(PWR PACTEL)一回路系统蒸汽发生器为研究对象,首先,基于流体一维流动模型的质量、动量和能量守恒方程建立管道进出口压降以及传热与流体流量之间的关系;其次,以遗传算法为基础开发倒U型管蒸汽发生器流量分配计算程序,采用基准实验对程序正确性和可靠性开展验证;最后,利用流量分配程序计算蒸汽发生器倒U型管管组的流量分布情况,研究管高、管长以及一/二次侧换热系数对蒸汽发生器内流量分配的影响。结果表明,所开发流量分配程序计算结果与实验吻合良好;在选定的自然循环工况下,该蒸汽发生器中长管更易发生倒流,且倒流现象呈现分布范围广、单管流量低的特点;倒U型管内正流流速与管长成反比,与管高成正比,倒流流速随着管长的增加保持不变,与管高呈反比关系;传热系数较低时,总流量与传热系数成反比关系,当传热系数高于特定值后部分管内发生倒流,总流量骤降。 相似文献
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当压水堆处于自然循环工况时,蒸汽发生器U型管内可能发生倒流现象,导致一回路流动阻力增大、自然循环流量降低,为反应堆安全运行带来不利影响。基于RELAP5程序建立了海洋条件下的附加力模型及控制体空间坐标求解模型,对蒸汽发生器所有U型管进行建模和节点划分,计算了海洋条件下蒸汽发生器内U型管的倒流临界质量流量及进出口压差,最后分析了3种海洋条件对U型管内流体倒流的影响。结果表明,倾斜条件下有可能会改变倒流现象;而在航行过程中可能遇到的起伏条件都无法改变倒流现象;当摇摆条件比较剧烈时有可能改变倒流现象。 相似文献
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The vapor pressures of CdI2 and Cs2CdI4 were measured below and above their melting points, employing the transpiration technique. The standard Gibbs energy of formation ΔfG° of Cs2CdI4, derived from the partial pressure of CdI2 in the vapor phase above and below the melting point of the compound could be represented by the equations ΔfG°Cs2CdI4 (±6.7) kJ mol−1=−1026.9+0.270 T (643 K≤T≤693 K) and ΔfG°{Cs2CdI4} (±6.6) kJ mol−1=−1001.8+0.233 T (713 K≤T≤749 K) respectively. The enthalpy of fusion of the title compound derived from these equations was found to be 25.1±10.0 kJ mol−1 compared to 36.7 kJ mol−1 reported in the literature from differential scanning calorimetry (DSC). The standard enthalpy of formation ΔfH°298.15 for Cs2CdI4 evaluated from these measurements was found to be −918.0±11.7 kJ mol−1, in good agreement with the values −920.3±1.4 and −917.7±1.5 kJ mol−1 reported in the literature from two independent calorimetric studies. 相似文献
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Zilu ZHAO 《等离子体科学和技术》2018,20(11):115403
In this paper, volume barrier discharge with different gap distances is added on the discharge border of high-voltage electrode of annular surface barrier discharge for generating volume added surface barrier discharge (V-SBD) excited by bipolar nanosecond high-voltage pulse power in atmospheric air. The excited V-SBDs consist of surface barrier discharge (d=0 mm) and volume added surface barrier discharges (d=2 mm and 3 mm). The optical emission spectra are recorded for calculating emission intensities of N2 (C 3Ⅱu →B3Πg ) and N2+ (B 2Σu+ → X 2Σg+ ), and simulating rotational and vibrational temperatures. The influences of gap distance of V-SBD on emission intensity and plasma temperature are also investigated and analyzed. The results show that d=0 mm structure can excite the largest emission intensity of N 2 (C 3 Πu →B 3Πg ), while the existence of volume barrier discharge can delay the occurrence of the peak value of the emission intensity ratio of N2+ (B 2Σu+ → X 2Σg+ )/N 2(C3Πu →B3Πg ) during the rising period of the applied voltage pulse and weaken it during the end period. The increasing factor of emission intensity is effected by the pulse repetition rate. The d=3 mm structure has the highest threshold voltage while it can maintain more emission intensity of N2(C3 Π u →B 3Πg ) than that of d=2 mm structure. The structure of d=2 mm can maintain more increasing factor than that of the d=3 mm structure with varying pulse repetition rate. Besides, the rotational temperatures of three V-SBD structures are slightly affected when the gap distance and pulse repetition rate vary. The vibrational temperatures have decaying tendencies of all three structures with the increasing pulse repetition rate. 相似文献
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The EMF of the following galvanic cells, (render) (render) were measured as a function of temperature. With O2 (1 atm.), RuO2 as the reference electrode, measurements were possible at low temperatures close to the melting point of Pb. Standard Gibbs energy of formation, ΔfG0mβ-PbO was calculated from the emf measurements made over a wide range of temperature (612–1111 K) and is given by the expression: ΔfG0mβ-PbO±0.10 kJ=−218.98+0.09963T. A third law treatment of the data yielded a value of −218.08 ± 0.07 kJ mol−1 for the enthalpy of formation of PbO(s) at 298.15 K, ΔfH0mβ-PbO which is in excellent agreement with second law estimate of −218.07 ± 0.07 kJ mol−1. 相似文献
Kanthal,Re,Pb,PbOCSZO2 (1 atm.),Pt
Kanthal,Re,Pb,PbOCSZO2(1 atm.),RuO2,Pt
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空间核反应堆是空间核电源和核推进的研究基础,大功率核反应堆的体积和质量一直是限制航空航天设计的重要因素。针对这一问题,本文对MW级空间核反应堆系统热管式辐射散热器进行建模和分析,建立热管式辐射散热器的热阻模型,利用穷举法和遗传算法在给定工况下探讨裸碳纤维翅片长度Lf和厚度δf、冷却剂质量流量m、辐射散热器入口温度Tf1对散热器质量M的影响。结果表明,当Tf1=800 K、Lf=5 cm、δf=0.16 mm、m=9 kg/s时,M达到最优,为906.593 kg,优化了0.63%的系统质量。 相似文献
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Xiaolong ZHU 《等离子体科学和技术》2022,24(2):25102
Based on the conventional tokamak HL-2A-like parameters and profiles, the linear properties and the nonlinear dynamics of non-resonant kink mode (NRK) and non-resonant fishbone instability (NRFB) in reversed shear tokamak plasmas are investigated by using the global hybrid kinetic-magnetohydrodynamic nonlinear code M3D-K. This work mainly focuses on the effect of passing energetic-ions on the NRK and NRFB instabilities, which is different from the previous works. It is demonstrated that the NRFB can be destabilized by the passing energetic-ions when the energetic-ion beta βh exceeds a critical value. The transition from NRK to NRFB occurs when the energetic-ion beta βh increases to above a critical value. The resonance condition responsible for the excitation of NRFB is interestingly found to be satisfied at ωt + ωp ≈ ω, where ωt is the toroidal motion frequency, ωp is the poloidal motion frequency and ω is the mode frequency. The nonlinear evolutions of NRFB's mode structures and Poincaré plots are also analyzed in this work and it is found that the NRFB can induce evident energetic-ion loss/redistribution, which can degrade the performance of the plasmas. These findings are conducive to understanding the mechanisms of NRFB induced energetic-ion loss/redistribution through nonlinear wave-particle interaction. 相似文献
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Panagiotis SVARNAS 《等离子体科学和技术》2013,15(9):891-895
Optical emission spectroscopy parallel to the axis of a low-pressure radio-frequency discharge in nitrogen was realized,i.e.end-on instead of customary side-on measurements.A specially designed optical feedthrough was fabricated and installed co-planar with the anode electrode,allowing non-invasive observations perpendicular to the plasma sheath.The principal excited species flowing towards the grounded electrode were identified and,by assuming Boltzmann distributions,the vibrational temperature of the molecules on the X1∑+g and C3Πu levels was estimated under various operating conditions. 相似文献
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The Pd-rich region of the isothermal section of the ternary U---Sn---Pd system at 1050°C was investigated by metallography, X-ray microanalysis and X-ray diffraction. The fcc -Pd(Sn, U) solid solution dissolves up to 16 at.% Sn and 15 at.% U. The AuCu3 type phases SnPd3 and UPd4 are the end members of a single-phase region. SnPd2 and UPd3 are in equilibrium with this solid solution of the composition U0.68Sn0.32Pd3 and with the ternary phase USnPd2. The Gibbs energies of formation of SnPd2, SnPd3 and UPd4 were used and ideal behaviour of the (Sn, U) Pd3+x solid solution was assumed to calculate the Gibbs energy of formation of UPd3 which gives ΔfG° = −312 kJ/mol at 1050°C. In addition, the annealing experiments in the Pd-rich region of the binary U---Pd system were extended to 950°C which confirm the phase-field distribution established at 1050°C in earlier work. 相似文献
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The oxygen potentials over the phase field: Cs4U5O17(s)+Cs2U2O7(s)+Cs2U4O12(s) was determined by measuring the emf values between 1048 and 1206 K using a solid oxide electrolyte galvanic cell. The oxygen potential existing over the phase field for a given temperature can be represented by: Δμ(O2) (kJ/mol) (±0.5)=−272.0+0.207T (K). The differential thermal analysis showed that Cs4U5O17(s) is stable in air up to 1273 K. The molar Gibbs energy formation of Cs4U5O17(s) was calculated from the above oxygen potentials and can be given by, ΔfG0 (kJ/mol)±6=−7729+1.681T (K). The enthalpy measurements on Cs4U5O17(s) and Cs2U2O7(s) were carried out from 368.3 to 905 K and 430 to 852 K respectively, using a high temperature Calvet calorimeter. The enthalpy increments, (H0T−H0298), in J/mol for Cs4U5O17(s) and Cs2U2O7(s) can be represented by, H0T−H0298.15 (Cs4U5O17) kJ/mol±0.9=−188.221+0.518T (K)+0.433×10−3T2 (K)−2.052×10−5T3 (K) (368 to 905 K) and H0T−H0298.15 (Cs2U2O7) kJ/mol±0.5=−164.210+0.390T (K)+0.104×10−4T2 (K)+0.140×105(1/T (K)) (411 to 860 K). The thermal properties of Cs4U5O17(s) and Cs2U2O7(s) were derived from the experimental values. The enthalpy of formation of (Cs4U5O17, s) at 298.15 K was calculated by the second law method and is: ΔfH0298.15=−7645.0±4.2 kJ/mol. 相似文献
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R. Subasri T. Mathews K. Swaminathan O. M. Sreedharan 《Journal of Nuclear Materials》2002,300(2-3):237-241
The sodium potential in the test electrode (a) Pt,O2,Na2ZrO3,ZrO2 was measured by using the emf technique employing Na-β″-alumina as the solid electrolyte in conjunction with (b) Pt,O2,Al2O3,NaAl11O17, (c) Pt,O2,Na2MoO4,Na2Mo2O7 and (d) Pt,Na2CO3,CO2,O2 as the reference electrodes over the ranges 880–1045, 700–800 and 850–940 K, respectively. The emf results between electrodes (b) and (c) were utilized for internal consistency checks. From the results on cells formed between (a) and (b) and those on (a) and (c), the standard Gibbs energy of formation, ΔfGo (kJ/mol) of Na2ZrO3 was determined to be −1699.4+0.3652T (K) valid over the temperature range 700–1045 K. The break in the emf data at 1045 K was corroborated by independent TG/DTA measurements carried out on Na2ZrO3 which exhibited an endotherm at 1055 K indicative of a phase transition in Na2ZrO3. 相似文献
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自然循环条件下,蒸汽发生器并联U型管束内存在单相流动不稳定性,部分U型管内存在倒流现象,对反应堆非能动安全产生负面影响。本文通过对基本守恒方程无量纲处理,采用线性扰动分析理论,获得了U型管内流动不稳定性判断准则(特征格拉晓夫数)。结果表明,当U型管格拉晓夫数高于特征格拉晓夫数时,管内流动是不稳定的,会出现倒流现象。以某型蒸汽发生器为对象,对U型管束流动不稳定性进行判断,通过与现有判别方法进行对比,验证了建立的U型管内流动不稳定性的判别方法。在此基础上,分析了蒸汽发生器一次侧流体入口密度对倒流现象的影响,发现当入口密度降低时,倒流现象更容易发生。本文结论可为蒸汽发生器优化设计提供一定的理论支持。 相似文献