中国先进研究堆热水层热工分析

中国先进研究堆(CARR)热水层(HWL)是反应堆水池上部形成的一层温度稍高的热水,它可以阻止水池下部含有较高放射性物质的水通过对流到达池水表面,从而降低反应堆大厅内的放射性剂量水平。本文采用经验公式计算了建立热水层所需的加热功率,并采用计算流体力学软件CFX分析了堆水池内流场和温度场。结果表明,CARR热水层的加热功率为120kw;在水池表面形成了热水层,但热水层的厚度不均,平均厚度约1．8m,最薄处约0．5m。

热网热水锅炉大修工程技术经济分析及造价控制

文章主要分析了锅炉大修前后相关热指标的变化,探究了锅炉大修的技术必要性和经济合理性,旨在为实现冬季调峰供热提供技术和经济保障、为供热企业缩减成本提供理论依据。

蒸汽喷入过冷液面接触冷凝实验研究

对饱和蒸汽垂直喷入过冷液面直接接触冷凝进行了可视化实验,观察到近液面层汽液两相作用区的凝结现象,研究了系统压力响应特性,提出将蒸汽凝结过程分为"压力平衡"和"压力稳定"两个阶段,根据实验结果回归了不同凝结模式下平均凝结换热系数的实验关联式.通过对温度场的分析、得到了热水层的分布规律.

饱和蒸汽在过冷液面凝结特性的实验研究

实验研究了堆芯补水箱上部加装遮流板时,饱和蒸汽在过冷液面上直接接触冷凝的瞬态特性。研究表明,遮流板改变了蒸汽射流的方向,减弱了近液面层的波动,降低了蒸汽的凝结速率,使堆芯补水箱中热水层的厚度减小,系统压力响应时间缩短。与无遮流板相比,实验初期水表面凝结换热系数降低76%～92%,总凝结量减少67%以上。

考虑浮力射流近区垂向效应影响的二维计算方法

以温排水数值计算为例,结合已有的深水表面浮力射流厚度研究,尝试给出了一种在排放口近区考虑射流垂向效应、在全计算域使用二维平面模型的计算方法。该方法在排放口引入了浮力射流热水层厚度,并且对混合区底部高程的变化过程给予考虑,提高了排放口近区表面温升分布的可信度,在火核电厂温排水数值预报中具有实用价值。

遮流板对CMT内蒸汽凝结影响的实验

为了延缓CMT内饱和蒸汽在过冷液面的凝结率,在CMT上部安装了遮流板,并对加装遮流板后蒸汽的凝结特性进行了实验研究。通过与无遮流板实验结果的比较,发现遮流板减缓了蒸汽对近液面层的扰动,减少了热水层的厚度,缩短了系统压力平衡时间,使实验初期水表面凝结换热系数降低了76%～92%。遮流板的使用可以有效提高反应堆非能动注水系统的安全性。

Numerical Analysis of Doublet Wells for Cold Energy Storage on Heat Damage Treatment in Deep Mines

Deep mining is an inevitable tendency in the development of coal industry. There are many heat damage problems with the increase of mining depth. The technology of using doublet wells, together with Heat Exchange Machine Systems （HEMSs）, to store cold energy is a key to solve the heat damage problems in deep mines. Based on the geological conditions, thermodynamic and hydraulic parameters of Jiahe Mine, the isotherms in the period of cold energy storage and refrigeration and the volumes of cold water within different temperature ranges of the cold energy storage well were numerically analyzed. The results show that 1） with the same pumped and injected water volumes, the lower the temperature of injected water is, the larger the volume.of cold water in the cold energy storage well is. With the larger volume, the effect of cold energy storage is better. 2） the larger the volumes of pumped and reinjected water frigeration is better. And 3） without disturbance, the volume and temperature of cold water in the cold energy storage well can keep unchanged or have only a little change for a long time. Therefore the technology of doublet wells for cold energy storage is feasible and the cold energy storage aquifers can meet the requirement of the technology.

Modeling vertical heat transport in the wave affected surface layer of the ocean

In considering the vertical heat boundary approximation for the free surface applied. However, due to the existence of the transport problems in the upper ocean, the flat upper and the horizontal homogenous hypothesis are usually wave motion, the application of this approximation may result in some errors to the solar irradiation since it decays quickly in respect to the actual thickness of the water layer below the surface; on the other hand, due to the fluctuation of the water layer depth, it is improper to neglect the effects of the horizontal advection and turbulent diffusion since they also contribute to the vertical heat transport. A new model is constructed in this study to reflect these effects. The corresponding numerical simulations show that the wave motion may remarkably accelerate the vertical heat transferring process and the variation of the temperature in the wave affected layer appears in an oscillating manner.

Hydrothermal Synthesis of Exfoliative LDH in the Presence of Glycine

Exfoliative Mg/Al layered double hydroxide （Mg/Al-LDHGly） was obtained via hydrothermal synthesis in the presence of glyeine. The product prepared by hydrothermal reaction for 10 h at 120℃possesses high thermal stability and maximal erystallite size in a, c directions. TEM and SEM analyses show that Mg/Al-LDHGly was of well-crystallized hexagonal product with stacks of slightly curved layers. Benefiting from mechanism investigation on its gradual delamination in formamide, rapid delamination of Mg/Al-LDHGly at room temperature was realized, which provided fundamental for preparation of （Mg/Al-LDHGly）/polymer nanoeomposites by using exfoliation-adsorption method.

Variation characteristics of aquifer parameters induced by groundwater source heat pump operation under variable flow

The variation characteristics of aquifer parameters,induced by groundwater source heat pump(GWSHP) operation under variable flow,were theoretically analyzed through a case study,in which the characteristics of building air conditioning load were considered.The results,compared with the constant flow operation,indicate that the influence on the variations of porosity,hydraulic conductivity and confined water head is decreased by 48%,51% and 71%,respectively,under variable flow operation.The security of variable flow operation is superior to that of constant flow.It is also concluded that the climate region and function of the buildings are primary factors which affect the suitability of variable flow operation in GWSHP.

An experimental comparison of water based alumina and silica nanofluids heat transfer in laminar flow regime

Experimental investigations were carried out to determine the Al2O3/water and SiO2/water nanofluids flowing through a circular tube. convective heat transfer performance and pressure drop of Measurements show that the addition of small amounts of nano-sized Al2O3 particles to the base fluid increases heat transfer coefficients considerably, while the result for the silica nanofluids contradicts with the alumina nanofluids and this leads to some interesting results. In the case of alumina nanofluids, an average increase of 16% in convective heat transfer coefficient is observed with an average penalty of 28% in pressure drop. Moreover, flow resistance increases significantly compared to the base fluid even at very low concentrations of nanofluids. Finally, measured heat transfer coefficients are compared with predicted ones from the correlation of Shah under the same conditions.

Effects of Elevated Air Temperatures on Soil Thermal and Hydrologic Processes in the Active Layer in an Alpine Meadow Ecosystem of the Qinghai-Tibet Plateau

In this study,effects of elevated air temperatures on thermal and hydrologic process of the shallow soil in the active layer were investigated. Open-top chambers(OTCs)were utilized to increase air temperatures 1-2℃ in OTC-1 and 3-5℃ in OTC-2 in the alpine meadow ecosystem on the Qinghai- Tibetan Plateau.Results show that the annual air temperatures under OTC-1 and OTC-2 were 1.21℃ and 3.62℃ higher than the Control,respectively.The entirely-frozen period of shallow soil in the active layer was shortened and the fully thawed period was prolonged with temperature increase.The maximum penetration depth and duration of the negative isotherm during the entirely-frozen period decreased, and soil freezing was retarded in the local scope of the soil profile when temperature increased.Meanwhile, the positive isotherm during the fully-thawed period increased,and the soil thawing was accelerated.Soil moisture under different manipulations decreased with the temperature increase at the same depth. During the early freezing period and the early fully- thawed period,the maximum soil moisture under the Control manipulation was at 0.2 m deep,whereas under OTC-1 and OTC-2 manipulations,the maximum soil moisture were at 0.4-0.5 m deep. These results indicate that elevated temperatures led to a decrease of the moisture in the surface soil.The coupled relationship between soil temperature and moisture was significantly affected by the temperature increase.During the freezing and thawing processes, the soil temperature and moisture under different manipulations fit the regression model given by the equationθV=a/{1+exp[b(TS+c)]}+d.

Heat Transfer and Friction Characteristics of Wavy Fin with Hydrophilic Coating under Dehumidifying Conditions

An experimental study on the airside heat transfer and friction characteristics of seven hydrophilic-coated wavy finned tube heat exchangers is performed under dehumidifying conditions. The effects of fin pitch, number of tube rows and inlet air relative humidity on the airside characteristics are investigated. The airside heat transfer and friction characteristics are presented in the form of Colburn factor and friction factor, respectively. The test results indicate that the Colburn factor and friction factor increase with decreasing fin pitch. The Colburn factor of 2 tube row heat exchanger is higher than that of 3 row heat exchanger, while their friction factors are nearly equal. As the inlet relative humidity increases, the Colburn factor increases and the friction factor is almost unchanged. The airside heat transfer and friction correlations are proposed for the hydrophilic-coated wavy fin with mean deviations of 6.5% and 9.1%, respectively. They can be used to design or evaluate hydrophilic-coated wavy fin-and-tube heat exchangers.

Characterization of deep ground geothermal field in Jiahe Coal Mine

Research into the characteristics of geothermal fields is important for the control of heat damage in mines. Based on measured geothermal data of boreholes from 200 m to 1200 m in a Jiahe Coal Mine, we demonstrate non-linear but increasing relations of both geo-temperatures and geothermal gradients with increases depth. Numerically, we fitted the relationship between geo-temperatures and depth, a first-order exponential decay curve, formulated as: T(h) = 4.975 + 23.08 exp(h/1736.1).

A New Approach for Classifying Two Types of El Nio Events

In recent decades, the typical E1 Nifio events with the warmest SSTs in the tropical eastern Pacific have become less common, and a different of E1 Nifio with the wannest SSTs in the central the east and west by cooler Pacific, which is flanked on SSTs, has become more frequent. The more recent type of E1 Nifio was referred to as central Pacific E1 Nifio, warm pool E1 Nifio, or dateline E1 Nifio, or the E1 Nifio Modoki. Central Pacific E1 Nifio links to a different tropical-to-extratropical teleconnection and exerts different impacts on climate, and several clas- sification approaches have been proposed. In this study, a new classification approach is proposed, which is based on the linear combination （sum or difference） of the two leading Empirical Orthogonal Functions （EOFs） of tropi- cal Pacific Ocean sea surface temperature anomaly （SSTA）, and the typical E1 Nifio index （TENI） and the central E1 Nifio index （CENI） are able to be derived by projecting the observed SSTA onto these combinations. This classification not only reflects the characteristics of non-orthogonality between the two types of events but also yields one period peaking at approximate two to seven years. In particular, this classification can distin- guish the different impacts of the two types of events on rainfall in the following summer in East China. The typi- cal E1 Nifio events tend to induce intensified rainfall in the Yangtze River valley, whereas the central Pacific El Nifio tends to induce intensified rainfall in the Huaihe River valley. Thus, the present approach may be appropriate for studying the impact of different types of E1 Nifio on the East Asian climate.

Relationship Between Upper-Ocean Heat Content in the Tropical Indian Ocean and Summer Precipitation in China

An analysis of the Ishii ocean heat content(OHC) in the tropical Indian Ocean from the surface to 700-m depth shows that the OHC changes dramatically on the interannual timescale in the Indian Ocean.The first mode of empirical orthogonal function(EOF1) of the OHC shows that there is a strong air-sea interaction pattern in the Indian Ocean with a positive(negative) loading in the east and a negative(positive) loading in the west.This seesaw oscillation pattern influences the summer precipitation in China with a North-South reversed distribution.Composite analysis shows that during a positive(negative) OHC episode,an anomalous cyclonic(anticyclonic) circulation over the western Pacific and South China weakens(enhances) the monsoonal northward flow in the lower troposphere;meanwhile,anomalous meridional circulation connects the descending(ascending) branch over the Southeast Indian Ocean and the ascending(descending) branch in South China as well as a descending(ascending) branch over North China.Analysis of the mechanism behind these features suggests that(1) the accumulation of OHC-induced vorticity is related to the wave activity over the mid-latitudes and that(2) the meridional teleconnection induced by the Indo-Pacific air-OHC interaction appears over East Asia and the western Pacific.Both of these patterns can cause summer precipitation anomalies in China.

Long-term temperature variation of the Southern Yellow Sea Cold Water Mass from 1976 to 2006

This paper discusses the long-term temperature variation of the Southern Yellow Sea Cold Water Mass(SYSCWM)and examines those factors that infl uence the SYSCWM,based on hydrographic datasets of the China National Standard Section and the Korea Oceanographic Data Center.Surface air temperature,meridional wind speed,and sea surface temperature data are used to describe the seasonal changes.Mean temperature of the two centers of the SYSCWM had diff erent long-term trends.The temperature of the center in the west of the SYSCWM was rising whereas that of the center in the east was falling.Mean temperature of the western center was related to warm water intrusion of the Yellow Sea Warm Current,the winter meridional wind,and the winter air temperature.Summer process played a primary role in the cooling trend of temperature in the eastern center.A decreasing trend of salinity in the eastern half of the SYSCWM showed that warm water intrusion from the south might weaken,as could the SYSCWM circulation.Weakened circulation provided less horizontal heat input to the eastern half of the SYSCWM.Less lateral heat input may have led to the decreasing trend in temperature of the eastern center of the SYSCWM.Further,warmer sea surface temperatures and less heat input in the deep layers intensifi ed the thermocline of the eastern SYSCWM.A stronger thermocline had less heat fl ux input from upper layers to this half of the SYSCWM.Stronger thermocline and weakened heat input can be seen as two main causes of the cooling temperature trend of the eastern center of the SYSCWM.