均匀加热竖直管内强迫对流临界热流密度的实验研究

利用氟里昂－１２作为工作流体，对于均匀加热竖直管内强迫对流的临界热流密度（ＣＨＦ）进行了实验研究。在比较广泛的参数范围内对质量流速Ｇ，压力Ｐ和热平衡干度Ｘ对ＣＨＦ的影响进行了探讨。结果表明，干度和质量流速对ＣＨＦ的影响规律与其他作者获得的结果相类似。但压力对ＣＨＦ的影响规律比较复杂。压力的影响与质量流速、干度密切相关。即在不同的质量流速和不同的干度下，压力影响规律不同。当质量流速较高时，在低干度区ＣＨＦ随压力的升高而降低，干度较高时，ＣＨＦ随压力升高而增大。     

竖直圆管下降流过渡沸腾传热实验研究

采用热块骤冷实验技术、非稳态一维数值分析方法和多元回归分析技术对竖直圆形元件管内下降流过渡沸腾传热特性进行了研究，建立了一组以ＣＨＦ点和最小膜态沸腾点（ＭＩＮ）为基础的过渡沸腾传热特性两点模型，和可以反映压力、流量和入口过冷度对过渡沸腾曲线影响的多变量数据分析模型。采用一维非稳态数值分析方法建立热块及试验管的精细温场分布，推导管内壁温度和热流密度，采用本文的模型和多元回归分析技术整理实验数据，得到一组过渡沸腾传热特性的半经验关系式，其适用于：Ｇ＝７０－２２５６ｋｇ／ｍ２·ｓ；Ｐ＝０．３－１６ＭＰａ；ΔＴｓｕｂ＝６℃－７５℃；预测结果与实验数据吻合较好。对主要流动参数对过渡沸腾传热特性的影响作了趋势分析和机理浅析。     

管内竖直向上流动水的临界热流密度研究

在高温高压回路上，对φ１０×１竖直管内临界热流密度现象进行了实验研究．实验参数范围为：压力ｐ＝６．３７～１４．７ＭＰａ；质量流速Ｇ＝５７１～５４６６ｋｇ／（ｍ２·ｓ）；人口欠热焓△ｈｉｎ＝９６～７４４ｋＪ／ｋｇ．通过实验，得出了在上述参数范围内的临界热流密度关系式，并用实验数据对Ｂｉａｓｉ关系式和Ｂｏｗｒｉｎｇ关系式进行了评价．     

Purex流程中Tc的走向及其影响因素的研究

用逆流萃取串级实验方法研究动力堆乏燃料后处理流程中（包括ｌＡ、ｌＢ、２Ａ、２Ｂ、ｌＣ、２Ｄ槽）Ｔｃ的走向及其影响因素。采用模拟料液的串级实验结果表明，ｌＡ槽中影响Ｔｃ的回收率的主要因素是料液中的ｃ（ＨＮＯ＿３）及ｃ（Ｚｒ（ＮＯ＿３）＿４）。按推荐工艺流程条件，ｌＡ槽：ＤＦ＿（Ｔｃ）＝６．５，ｃ（ＨＮＯ＿３）＝２．０ｍｏｌ／ｌ；ＤＦ＿（Ｔｅ）＝７．８，ｃ（ＨＮＯ＿３）＝３．０ｍｏｌ／ｌ；ｌＢ槽：ＤＦ＿（ＴＣ）≈５６０—７７０；２Ａ槽：ＤＦ＿（ＴＣ）＝３７０；２Ｂ槽：ＤＦ＿（ＴＣ）＝１．２；ｌＣ槽：ＤＦ＿（ＴＣ）＝１．１；２Ｄ槽：ＤＦ＿（ＴＣ）＝３０．３。     

心肌显像剂^68Ga（BAT—TECH）的一些基本常数测定

研究了心肌显像剂＾６８Ｇａ（ＢＡＴ－ＴＥＣＨ）的动力学性质，测定了它的热力学常数。实验结果表明，ＢＡＴ－ＴＥＣＨ与柠檬酸镓的配体交换反应为二级反应，反应速率常数ｋ为０．５０ｌ／ｍｏｌ．ｓ，反应活化能Ｅａ＝５６．６ｋＪ／ｍｏｌ；＾６７Ｇａ（ＢＡＴ－ＴＥＣＨ）的稳定常数Ｉｇβ＝１４。９，配体ＢＡＴ－ＴＥＣＨ的四级氢解离常数ｐＫ１＝４．６２，ｐＫ２＝７．６８，ｐＫ３＝８．６８，ｐＫ４＝１１．２。     

心肌显像剂~（68）Ga（BAT－TECH）的一些基本常数测定

研究了心肌显像剂￣（６８）Ｇａ（ＢＡＴ－ＴＥＣＨ）的动力学性质，测定了它的热力学常数。实验结果表明，ＢＡＴ－ＴＥＣＨ与柠檬酸镓的配体交换反应为二级反应，反应速率常数ｋ为０．５０ｌ／ｍｏｌ·ｓ，反应活化能Ｅ＿ａ＝５６．６ｋＪ／ｍｏｌ；￣（６８）Ｇａ（ＢＡＴ－ＴＥＣＨ）的稳定常数ｌｇβ＝１４．９，配体ＢＡＴ－ＴＥＣＨ的四级氢解离常数ｐＫ＿１＝４．６２，ｐＫ＿２＝７．６８，ｐＫ＿３＝８．６８，ｐＫ＿４＝１１．２。     

离子交换色层地分离和富集水中微量有机胂

研究了用阳离子交换色层法分离和富集水中甲基胂酸（ＭＭＡ）和二甲基胂酸（ＤＭＡ）的实验条件。对样品的吸附酸度、淋洗液的组成及淋洗速度进行了选择。在吸附酸度ＰＨ＝２条件下,用６０ｍＬ０．５ｍｏｌ／Ｌ,ＣＨ３ＣＯＯＨ－ＣＨ３ＣＯＯＮＨ４（ｐＨ＝４．７）洗脱ＭＭＡ,继续用６０ｍＬ３ｍｏｌ／ＬＮＨ３．Ｈ２Ｏ洗脱ＤＭＳ,淋洗速度控制在０．１～０．１５ｍＬ／ｍｉｎ,洗脱液用吕了活化法进行测定。实际水样的加标回收     

水和氟里昂在垂直管内上升和下降流动时的CHF值及流动方向因子

分析比较了水和氟里昂介质在垂直圆管内向上流动(正流)和向下流动(倒流)的临界热流密度(CHF)试验数据(水数据298个,氟里昂数据323个)。结果表明,在一定的流动工况下,流动方向对CHF值有明显的影响。直接将上升流数据与下降流数据比较或用上升流公式计算下降数据,其总均方根偏差为6%-14%。上升流CHF试验值大于下降流,但在小临界含汽量区,下降流试验值开始等于和大于上升流试验值。根据上升流与下降流CHF值差异产生机理,提出一形如C=bl·(X_1)~(b2)·(R_(el))~(b3)·(ρ_1/ρ_9)~(b4)的流动方向修正因子。该修正因子有较宽的适用范围,除适用于水数据外,还可用于经过模化处理后的氟里昂的CHF试验值修正。修正后,试验值与计算值的总均方根偏差减小20%-46%,偏差带和最大偏差也有不同程度的减小。     

离子交换色层法分离和富集水中微量有机胂

研究了用阳离子交换色层法分离和富集水中甲基胂酸（ＭＭＡ）和二甲基胂酸（ＤＭＡ）的实验条件。对样品的吸附酸度、淋洗液的组成及淋洗速度进行了选择。在吸附酸度ｐＨ＝ ２ 条件下,用６０ ｍ Ｌ０．５ ｍ ｏｌ／ＬＣＨ３ＣＯＯＨ－ＣＨ３ＣＯＯＮＨ４（ｐＨ＝ ４．７）洗脱ＭＭＡ,继续用６０ ｍ Ｌ ３ｍ ｏｌ／ＬＮＨ３·Ｈ２Ｏ洗脱ＤＭＡ,淋洗速度控制在０．１～０．１５ ｍ Ｌ／ｍ ｉｎ,洗脱液用中子活化法进行测定。实际水样的加标回收率：ＭＭＡ为（９６±２）％ ,ＤＭＡ为（１０３±３）％ ,它们的相对标准偏差分别为６％ 和３％ 。     

亚硝酸与正丁醛和Np（Ⅵ）反应的动力学研究

研究了（１）ＨＮＯ２与正丁醛的反应，得速率方程为：－ｄｃＨＮＯ２／ｄｔ－ｋ１ｃＨＮＯ２．ｃｎ－ｃ３Ｈ７ＣＨＯ．ｃＨＮＯ３，在２０℃、Ｉ＝２．０ｍｏｌ／ｋｇ时，速率常数Ｋ１＝０．７６ｌ＾２（ｍｏｌ＾２．ｍｉｎ）（２）在固定１．０ｍｏｌ／ｌＨＮＯ３条件下，ＨＮＯ２与Ｎｐ（Ⅵ）的反应，得速率方程为：－ｄｃＮｐ（Ⅵ）ＣＨＮＯ２在２０℃、Ｉ＝２．０ｍｏｌ／ｋｇ时，表观速率常数ｋ３＾１＝９３ｌ／ｍｏ     

A flow boiling burnout correlation for water and Freon-12

An empirical correlation has been developed for calculating critical heat flux (CHF) for vertical upflow in uniformly heated tubes. The correlation is based on parameter groups derived from a dimensional analysis and has been compared with experimental CHF data for Freon-12 and for water. Except for coolant conditions in which (i) mass fluxes are less than 300 kg s⁻¹ m⁻², (ii) dryout qualities are below 10%, or (iii) water pressures are outside the range 3.5 to 12 MPa, the correlation agrees very favourably with the experimental data. The overall mean ratio of calculated to experimental CHF values for 1760 sets of Freon-12 data is 0.992 and the r.m.s. error 3.3%; the corresponding values for 2063 sets of water data are 0.982 and 5.8%. This provides a basis for predicting CHF levels over a wide range of coolant conditions, as required in the analysis of hypothetical loss-of-coolant accidents in water-cooled nuclear reactors.     

Comparison of correlations for predicting critical heat flux for uniformly heated vertical porous coated tubes at low pressure

The paper includes comparison of correlations for predicting critical heat flux for uniformly heated vertical porous coated tubes at pressure between 0.1 and 0.7 MPa. In this study, a total of 1120 data points of CHF (Critical heat flux) in uniformly heated vertical porous coated tubes were used. Accuracy of correlations was estimated by calculating average and RMS error with available experimental data, and a new correlation is presented. The new correlation predicts that the CHF data are significantly better than those currently available correlations, with average error 0.69% and RMS error 10.9%.     

Critical heat flux under zero flow conditions in vertical annulus with uniformly and non-uniformly heated sections

The experimental study of water CHF (critical heat flux) under zero flow conditions has been carried out in an annulus flow channel with uniformly and non-uniformly heated sections over a pressure range of 0.52–14.96 MPa. In the present boiling system, the CHFs occur in the upper region of the heated section, in contrast to the results in the experiments for boiling tubes conducted by several investigators. The general trend of the CHF with pressure is that the CHF increases up to a medium pressure of about 6–8 MPa and decreases as the pressure is further increased. A comparison of the present data with the existing flooding CHF correlations shows that the correlations depend greatly on the effect of the heat flux distribution. When the correction terms with the density ratio and the effect of the heat flux distribution proposed in the present work are used with the CHF correlation based on the Wallis flooding correlation, it predicts the measured flooding CHF within an RMS error of 9.0%.     

Critical heat flux of forced convection boiling in an oscillating acceleration field — I. General trends

The influence of periodically varying acceleration on critical heat flux (CHF) of Freon-113 flowing upward in a uniformly heated vertical annular channel has been studied experimentally. The freon loop was oscillated vertically to determine the ratio of CHF in the oscillating acceleration field to the corresponding stationary value. The amplitude of inlet flow oscillation induced by variation of acceleration, which causes early CHF, is proportional to the acceleration amplitude. The dependence of inlet flow rate on the oscillating acceleration decreases with increasing inlet subcooling, and no oscillation of inlet flow is observed in the case of negative exit quality (subcooled boiling). Nevertheless the degradation of CHF is more remarkable in the low quality region. This result suggests the necessity to introduce an other mechanism of early CHF than flow oscillation.     

Prediction of Liquid Film Dryout in Two-Phase Annular-Mist Flow in a Uniformly Heated Narrow Tube Development of Analytical Method under BWR Conditions

A method was developed based on the conservation lows to predict critical heat flux (CHF) causing liquid film dryout in two-phase annular-mist flow in a uniformly heated narrow tube under BWR conditions. The applicable range of the method is within the pressure of 3–9 MPa, mass flux of 500–2,000 kg/m²·s, heat flux of 0.33–2.0 MW/m² and boiling length-to-tube diameter ratio of 200–800.

The two-phase annular-mist flow was modeled with the three-fluid streams with liquid film, entrained droplets and gas flow. Governing equations of the method are mass continuity and energy conservation on the three-fluid streams. Constitutive equations on the mass transfer which consist of the entrainment fraction at equilibrium and the mass transfer coefficient were newly proposed in this study.

Confirmation of the present method were performed in comparison with the available film flow measurements and various CHF data from experiments in uniformly heated narrow tubes under high pressure steam- water conditions. In the heat flux range (q“<2MW/m²) practical for a BWR, agreement of the present method with CHF data was obtained as, (Averaged ratio)±(Standard deviation)=0.984±0.077, which was shown to be the same or better agreement than the widely-used CHF correlations.     

Parametric trends analysis of the critical heat flux based on artificial neural networks

Parametric trends of the critical heat flux (CHF) are analyzed by applying artificial neural networks (ANNs) to a CHF data base for upward flow of water in uniformly heated vertical round tubes. The analyses are performed from three viewpoints, i.e., for fixed inlet conditions, for fixed exit conditions, and based on local conditions hypothesis. Katto's and Groeneveld et al. dimensionless parameters are used to train the ANNs with the experimental CHF data. The trained ANNs predict the CHF better than any other conventional correlations, showing RMS errors of 8.9%, 13.1% and 19.3% for fixed inlet conditions, for fixed exit conditions, and for local conditions hypothesis, respectively. The parametric trends of the CHF obtained from those trained ANNs show a general agreement with previous understanding. In addition, this study provides more comprehensive information and indicates interesting points for the effects of the tube diameter, the heated length, and the mass flux. It is expected that better understanding of the parametric trends is feasible with an extended data base.     

Flooding limited CHF in a vertical 3 × 3 rod bundle with non-uniform axial heat flux

KAERI has performed an experimental study on the critical heat flux (CHF) under zero flow conditions with a non-uniformly heated 3 × 3 rod bundle. Experimental conditions are in the range of a system pressure from 0.50 to 14.96 MPa and inlet water subcooling enthalpies from 68 to 352 kJ/kg. The test section used in the present experiments consisted of a vertical flow channel, upper and lower plenums, and a non-uniformly heated 3 × 3 rod bundle. The experimental results show that the CHFs in low-pressure conditions are somewhat scattered within a narrow range. As the system pressure increases, however, the CHFs show a good parametric trend. The CHFs occur in the upper region of the heated section, but the locations of the detected CHFs move gradually in a downward direction with the increase of the system pressure. Even though the effects of the inlet water subcooling enthalpies and system pressure of the flooding CHF are relatively smaller than those of the flow boiling CHF, the CHF increases by increasing the inlet water subcooling enthalpies. Several existing correlations for the countercurrent flooding CHF based on Wallis's flooding correlation and Kutateladze's criterion for the onset of flooding are compared with the CHF data obtained in the present experiments to examine the applicability of the correlations.     

Critical heat flux during natural convective boiling in inclined tubes submerged in saturated liquids

An experimental study was carried out to improve and expand understanding of boiling phenomena and the critical heat flux (CHF) during natural convective boiling in uniformly heated inclined tubes submerged in a pool of saturated liquids under atmospheric pressure. The test conditions were as follows: inter diameters of the test tubes ranged from 0.9 to 8.0 mm; heated lengths ranged from 100 to 400 mm, and inclination angles varied from 30° to vertical position. The test fluids were water and R-11. The experimental results showed that the CHF decreases with the increasing ratio of the tube length to the tube diameter, and with the reducing of the inclination angle. A semi-theoretical correlation, which originally used for the CHF during natural convective boiling in vertical tubes, was modified to predict the CHF occurs in the inclined tubes. The modified correlation agreed reasonably well with the present experimental data and other CHF data for narrow inclined annular tubes.     

Fluid-to-fluid modeling of critical heat flux in 4 × 4 rod bundles

Fluid-to-fluid modeling of critical heat flux (CHF) is to simulate the CHF behaviors for water by employing low cost modeling fluid, and the flow scaling factor is the key to apply the technique to fuel bundles. The CHF experiments in 4×4 rod bundles have been carried out in Freon-12 loop in equivalent nuclear reactor water conditions (P=10.0–16.0 MPa, G=488.0–2100.0 kg/m² s, X_cr=−0.20–0.30). The models in fluid-to-fluid modeling of CHF is verified by the CHF data for Freon-12 obtained in the experiment and the CHF correlation for water obtained by Nuclear Power Institute of China (NPIC) in the same 4×4 rod bundles. It has been found that the S.Y. Ahmad Compensation Distortion model, the Lu Zhongqi model, the Groeneveld model and Stevens–Kirby model overpredict the bundles CHF values for water. Then an empirical correlation of flow scaling factor is proposed. Comparison of the CHF data in two kinds of test sections for Freon-12, in which the distance of the last grid away the end of heated length is different, shows that the spacer grid, which is located at 20 mm away from the end of the heated length, has evidently influenced on the CHF value in the 4×4 rod bundles for Freon-12. This is different from that for water, and the need for further work is required.     

An integral equation model for critical heat flux at subcooled and low quality flow boiling

A new theoretical model of critical heat flux (CHF) is developed for the flow boiling condition from bubble-detached to low quality range. The CHF condition is postulated to occur when the superheated liquid layer on the heated wall, which is formed under the bubbly layer from the point of the onset of significant void generation, is depleted due to the evaporation along the heated length. The model shows a very promising agreement with the uniformly heated round tube data for both water and refrigerants by simply applying well-known constitutive relationships without any tuning constant for the CHF data. The significance of the proposed model in unifying the existing models is also discussed.