Thermal management of high temperature polymer electrolyte membrane fuel cell stacks in the power range of 1–10 kWe

Maintaining optimal temperature of the stack is critical for efficient operation of high temperature polymer electrolyte membrane fuel cells. While a number of possibilities of thermal management exist for small stacks, the problem becomes more complicated for larger stacks. In the present study, the thermal management of stacks in the power range of 1–10 kWe is considered through computational fluid dynamics simulations. It is shown that large stacks need to have dedicated cooling plates through which a coolant is circulated. Further, stacks of the size of 10 kWe can have reasonably low cell temperature variations (∼20 K) only by passing pre-heated liquid coolant through the coolant plates. Estimates show that the concomitant increase in the coolant flow rate induces large pressure drops, of the order of 30 bar, if a four-parallel serpentine is used on an active cell area of 30 cm × 30 cm. It is therefore necessary to use parallel channel flow fields with carefully designed feeder manifolds to maintain optimal cell temperatures and reasonably low coolant pressure drops in large stacks.     

Molten salt cooled Encapsulated Nuclear Heat Source (ENHS)-like reactors

The feasibility of designing molten-salt cooled ENHS (Encapsulated Nuclear Heat Source)-like reactor cores with Pu¹⁵N-U¹⁵N nitride fuel for high temperature applications is assessed. The cores considered have uniform fuel composition and no blanket elements and solid reflectors. They are to operate for at least 20 effective full power years without refueling, without fuel shuffling and with burnup reactivity swing less than 0.52%. Three molten-fluoride-salts: NaF(57)-BeF₂(43), ⁷LiF(66)-BeF₂(34), and LiF(46.5)-NaF(11.5)-KF(42) are considered as the coolant and six materials: SS304, Hastelloy-N, HT-9, Mn-316SS, PCA, and SiC, are considered for the structures. It is found that, neutronically, ENHS-like cores can be designed for all combinations of molten-salt coolants and structural materials considered. Relative to the reference ENHS core, the molten-salt cooled cores require significantly tighter lattice, have softer neutron spectra, significantly more negative Doppler reactivity effect, much more positive coolant temperature and void reactivity effect and smaller reactivity worth of the control elements. Of the molten salts considered, LiF-NaF-KF offers the largest p/d ratio and is most suitable for natural circulation cooling.     

Structural integrity evaluation for interference-fit flywheels in reactor coolant pumps of nuclear power plants

This study is concerned with structural integrity evaluations for the interference-fit flywheels in reactor coolant pumps (RCPs) of nuclear power plants. Stresses in the flywheel due to the shrinkage loads and centrifugal loads at the RCP normal operation speed, design overspeed and joint-release speed are obtained using the finite element method (FEM), where release of the deformation-controlled stresses as a result of structural interactions during rotation is considered. Fracture mechanics evaluations for a series of cracks assumed to exist in the flywheel are conducted, considering ductile (fatigue) and non-ductile fracture, and stress intensity factors are obtained for the cracks using the finite element alternating method (FEAM). From analysis results, it is found that fatigue crack growth rates calculated are negligible for smaller cracks. Meanwhile, the material resistance to non-ductile fracture in terms of the critical stress intensity factor(K _IC) and the nil-ductility transition reference temperature RTinNDT are governing factors for larger cracks.     

高频焊接空冷器冷却管的研制

研制的３６ｍｍ×１４ｍｍ×１．５ｍｍ椭圆形高频焊接空冷器冷却管使用效果良好，为高频直缝焊管向多用途、高精度、高强度发展提供了经验。介绍了该产品的试制工艺及试制设备改进情况。高频焊接钢管，空冷器冷却管，研制     

竖直环形通道内过渡沸腾传热实验研究

用热块技术对低压、低质量流速下垂直环形通道中水的过渡沸腾传热进行实验研究，实验范围是：压力Ｐ＝２．５－１０．９ｂａｒ，质量流速Ｇ＝７４．２－２２３．９ｋｇ／ｍ２ｓ，进口过冷度△Ｔｓｕｂ＝５．５－３２．４℃。用一维和二维模型对实验数据分析处理，得到许多不同工况下的过渡沸腾曲线，并对影响过渡沸腾传热的主要因素进行了分析。实验发现，管壁的热流密度值在过渡沸腾区域有较大波动，表明过渡沸腾这种传热方式所固有的不稳定性。得到了一个预测过渡沸腾传热的公式，并和其他关系式进行了比较。     

Gas cooled fast reactor for generation IV service

The Gas Cooled Fast Reactor (GFR), which is among the Generation IV concepts under evaluation for future deployment, will have to satisfy the Gen IV goals in the area of sustainability, safety and economy. This paper discusses challenges posed by the GFR when striving for the achievement of balance among the above Generation IV goals, and the pros and cons of various design choices. Considering these goals, the currently preferred design direction at MIT is a GFR design using a direct supercritical CO₂ cycle, traditional containment with design pressure of 5 bars, employment of redundant active emergency cooling systems with highly reliable and diverse power supplies, which can also function in the passive mode as a backup at 5 bars containment pressure, and TRU fueled cores using either block-type (TRU-U)C fuel or pin type (TRU-U)C fuel with double cladding or (TRU-U)O₂ fuel vibropacked in a tube-in-duct assembly.     

高强化柴油机气缸套周围冷却水流动的数值模拟和试验研究

针对柴油机的冷却进行精确计算,必须对柴油机内部流场进行深入的三维数值模拟和试验研究。首先分析了柴油机冷却水流动的数值模拟计算方法,建立了某柴油机气缸套周围复杂水腔的三维实体模型,并采用FIRETM软件对水腔模型进行计算,得到冷却水在缸套复杂水腔内的三维流场;再运用流量压力测量法和流动显示法对透明气缸套水腔内的冷却水流动进行试验。对比分析结果表明数值模拟计算的冷却水流动方向和流量大小与试验测量和观察结果相一致缸套水腔改进后冷却水的流量和压力分布合理,水腔内微涡和流动死区减少,缸套穴蚀减轻,此数值模拟方法是合理的。     

车用内燃机冷却系的流动与传热仿真

本提出了车用内燃机冷却系的流动与传热仿真方法。采用一维的方法研究了车用内燃机冷却系的流动问题;采用集总参数法研究了车用内燃机冷却系的传热问题;将车用内燃机冷却系的流动问题与传热问题耦合起来作为一个系统,进行整体研究,建立了内燃机冷却系的流动与传热问题的整体模型。编制了计算程序。对某型坦克内燃机冷却系的流动与传热进行了实例计算,仿真结果与试验值符合较好。     

田湾核电站14C和3H年产生量估算

介绍了压水堆核电站堆芯燃料和冷却剂中14^C和3^H产生量的计算方法,计算了田湾核电站每年在堆芯燃料和冷却剂中产生的14^C和3^H的总活度,将该计算结果与俄罗斯在田湾核电站最终安全分析报告中给出的数据进行了比较分析,并从减少这两种核素产生量的角度提出了一些设计建议。     

Coolant system health monitoring and fault diagnosis via health parameters and fault dictionary

A new methodology is described for the condition monitoring and fault diagnosis of machine tool coolant systems. The steady state characteristics of the coolant system pump outlet pressure, pump motor temperature and tank level are used to define health parameters from which the system health is deduced. On detection of a significant change in system health the pressure transient on closure of the flow valve is captured to aid diagnosis of the fault. A demonstration system for the coolant system of a Wadkin V4-6 machine tool is described. This is used to verify the usefulness of the health system described above by simulation of a number of typical faults.