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双语推荐：流动沸腾

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以水为工质,在常压下对拥有细长回路和较长水平段的自然循环系统进行可视化实验研究,并以典型的实验现象(P=1.46kW)为例分析该系统的瞬态运行特性和不稳定性机理。结果表明:阻力系数较大的细长自然循环回路难以产生有效的单相自然循环,只能通过间歇性沸腾和两相流动将热量导出。这是因当回路阻力较大时,过冷沸腾产生的驱动力无法驱动回路产生有效的自然循环,而只有当加热段内流体发生饱和沸腾时才能驱动系统产生循环流动。较大的回路阻力和沸腾过程中产生的系统降压闪蒸是细长自然循环系统难以维持稳定的流动驱动压头从而产生间歇性沸腾和强烈流动不稳定性的根本原因。
The visual experimental study with water as the working substance was performed to investigate the operation behavior of a natural circulation system with elongated loops and long horizontal sections at atmospheric pressure ,and the transient operation behavior and instability mechanism of typical experimental phenomenon ( P=1.46 kW) were given .The results show that the single natural circulation in elongated system with the great resistance coefficient is difficult to appear ,but the heat can be removed by two-phase intermittent boiling .The driven force caused by the sub-cooled boiling can not drive the fluid to produce the effective natural circulation because of the great loop resistance ,and the circular flow occurs only when the fluid in heat section produces the saturation boiling .T he big loop resistance and flashing because of pressure drop in boiling process make the elongated natural circulation difficult to maintain a stable flow driven head and they are the fundamental r

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利用阳极氧化法在钛换热管内表面制备出了一层管阵列结构纳米薄膜。以该纳米管阵列表面管为传热元件,蒸馏水为工质,采用管外电加热竖管强制循环工艺,在恒质量流速下考察了纳米管阵列表面管的流动沸腾传热性能。在实验的基础上,得出了纳米管阵列表面管流动沸腾传热系数关联式。实验结果表明,与光滑表面管相比,流动沸腾传热温差降低了30%～55%,在没有增加阻力的情况下,沸腾传热系数提高了1.5～2.2倍。
A nano-film with structure of tube arrays was prepared on the inner surface of titanium tube via anodic oxidization. Taking deionized water as the working fluid,the flow boiling heat transfer properties of the nanoporous surface vertical tube with electrically heated outside surface were studied at constant mass velocity employed by forced circulation. The flow boiling heat transfer coefficient correlation of the tube was obtained. Compared to the smooth tube,the flow boiling heat transfer temperature differences were lowered 30%-55%,and its boiling heat transfer coefficient could be increased 1.5-2.2 times.

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为了得到适用于微小通道内流动沸腾换热的预测方法,本文以近些年发表的9篇文献中的2924个实验数据点组成数据库,考虑到随着通道直径减小,表面张力对微小通道内两相流动和换热的影响起到主要作用,将Chen形式的换热模型中的核态沸腾和对流换热两部分的修正系数进行了优化.沸腾抑制系数和对流增强系数由气相韦伯数、两相雷诺数、沸腾数、气泡抑制数等量纲为1数组成,反映出了表面张力、水力直径、流动条件、热力条件对于换热的综合影响.结果表明,拟合出的微小通道中沸腾换热的新模型,适于预测水力直径3 mm以下的细管道中CHF(临界热流密度)点以前的换热系数.与实验数据比较,新模型预测的平均绝对误差为19.0%.
In order to get a method for predicting the flow boiling heat transfer in mini-channels, 2924 experimental data of flow boiling in mini-channels from 9 literatures were analyzed. As the tube diameter decreases,the surface tension rather than the buoyancy affects the two phase flow and heat transfer. The enhancement factor of convective evaporation and suppression factor of nucleate boiling of Chen-type correlation were optimized. The non-dimensional number vapor Weber number,two-phase Reynolds number,boiling number and confinement number were used to express the effects of surface tension,diameter,flow conditions and heat flux. A new model was presented to predict the heat transfer coefficient of pre-dryout in mini-channels. A mean absolute deviation of 19.0%was achieved with this new correlation.

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本工作对由直径为8 mm的表面氧化后的碳钢球组成的填充床中的流动沸腾传热进行实验研究。通过逐步增加和减小热流密度的方式来控制沸腾起始与沸腾强度，监测到发生在填充床中的沸腾迟滞现象，研究了填充床中各种沸腾迟滞现象随着填充床内不同轴向和径向位置、表观流速等因素的变化规律。实验表明：高流速、远离出口、靠近管壁的情况不易出现成核滞后；增大表观流速、填充物表面粗糙度可增大沸腾湮灭滞后程度。
The boiling heat transfer on packed bed with 8 mm carbon steel balls was investigated . The boiling curves were obtained at the increasing and decreasing conditions of heat flux , which made it possible to detect the boiling hysteresis phenomena .The various factors which impact on the boiling hysteresis in the channels , such as the axial and radial positions in the test section ,the superficial flow velocity etc .,were investigated .The experimental results show that the nucleation hysteresis is weak at high liquid velocity ,far from the outlet and near wall situations .When liquid superficial velocity and surface roughness of the fillers increase , the degree of annihilation hysteresis of boiling increases .

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基于两流体欧拉数学模型结合RPI壁面沸腾模型,利用大型商用CFD软件ANSYS CFX 12.0对蒸汽发生器传热管束过冷沸腾区一次侧、壁面和二次侧耦合传热过程进行了数值模拟。研究了三叶梅花孔支撑板和不同入口过冷度条件下蒸汽发生器传热管束内的流动沸腾现象,得到一、二次侧流场与温度场,二次侧空泡份额分布,支撑板梅花孔局部的流动状况及不同入口过冷度对蒸汽发生器热工水力特性的影响。数值模拟结果表明,三叶梅花孔支撑板的存在及不同入口过冷度对蒸汽发生器传热管束过冷沸腾区域的热工水力特性影响显著。
Based on two fluid Euler model combining with RPI wall boiling model ,the coupled heat transfer among the primary side ,the tube wall and the secondary side in the subcooled boiling region of the heat transfer tube bundle of steam generator (SG) was simulated by using ANSYS CFX 12.0 code .The flow boiling phenomenon occurred in the heat transfer tube bundle of SG under trefoil orifice plate and different inlet subcooling conditions was researched . The velocity and temperature distributions of both the primary and the secondary sides ,the void fraction distribution of the secondary side ,the local flow characteristics around trefoil orifice plate ,and the effect of different inlet subcoolings on thermal-hydraulic characteristics of SG were acquired .Numerical simulated results show that the existence of trefoil orifice plate and inlet subcooling have a significant influence on thermal-hydraulic characteristics in the subcooled boiling region of the tube bundle of SG .

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为了发展适于螺旋管内流动沸腾传热系数关联式，基于流动沸腾传热机理，引入参数Dn 数来修正复杂管道对传热系数的影响，并经过回归计算确定Dn 数的指数，从而发展了螺旋管内流动沸腾传热系数关联式。进一步分析了传热系数预测值与实验值的偏差随流量、干度的变化情况。利用以R134a为介质的螺旋管传热实验数据验证了该关联式的适用性，并采用平均相对误差（the mean relative error，MRE）和均方根误差（the root mean square error，RMSE）来衡量预测结果的准确性，计算出MRE在8.23％范围内，RMSE为0.532。该平均相对误差值和均方根误差值都比较小，表明回归计算结果符合要求。因此，复杂管道引入参数Dn 数建立传热系数关联式是非常适用的，并值得推广应用。
In order to develop flow boiling heat transfer coefficient correlations for helically coiled tube,based on the mechanism of flow boiling heat transfer.The Dn factor was introduced to consider complex pipeline effects on flow boil-ing heat transfer.The index of the Dn factor was gained by using the regression method.And relation of the ratio of the experimental and predicted values with the mass flow rate and vapor quality was further analyzed.A new heat transfer coefficient correlation of flow boiling in helically coiled tube was developed.The applicability for the heat transfer coef-ficient correlation was validated by experimental data of flow boiling heat transfer in helically coiled tube with R134a. The MRE and the RMSE were used to measure the accuracy of regression results,with MRE and RMSE being 8.23%and 0.532,respectively.The MRE and the RMSE were small,the regression results conformed to the requirements. Therefore,the method is very applicable,and is worthy of popul

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利用UDF编程定义纳米流体相变源项，对Al2O3-H2O纳米流体在水平管内的沸腾过程进行了数值模拟，分析研究了纳米流体在水平管内沸腾的流型特点，结果表明水平管内沸腾蒸发产生的相变含气率沿着管长方向不断增加，但相同截面位置纳米流体的含气量高于纯水的含气量，有助于强化流体的扰动与混合。对于不同浓度的Al2O3-H2O纳米流体的流型研究表明：颗粒浓度对于纳米流体管内沸腾过程的影响不大。随后将纳米流体与纯水的流型进行比较，结果表明Al2O3-H2O纳米流体使得管内沸腾更剧烈，也更容易沸腾，这将改善水平圆管的流动特性。
Programming through a UDF definition of nanofluid phase change source term , the Al2 O3 -H2 O nanofluid boiling process is simulated in the horizontal tube ,and the boiling flow pattern characteristics analyzed in the nanofluid horizontal tube .The results show that for boiling in the horizontal pipe , the gas content increases along the length direction , but in the same interface position , the nanofluid of air content is higher than that of pure water of air content ,helpful to enhance the disturbance of the fluid .For different concentrations of Al 2 O3 -H2 O nanofluid flow pattern , particle concentration has little effect on nanofluid tube boiling process .Nanofluid is then compared with pure water flow pattern , the results show that the Al 2 O3 -H2 O nanofluid makes tube boiling more intense and easier .It will improve the flow characteristic of the horizontal circular tube .

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核电站蒸汽发生器二次侧为两相对流沸腾换热过程,在设计过程中须保证其不发生两相流不稳定性。本工作采用时域法对垂直上升管内两相流不稳定性进行研究,建立了垂直上升直管内流动沸腾过程的一维模型,并编制计算程序。采用该程序模拟了流动沸腾过程气液两相流密度波的不稳定性,给出两相流波动过程瞬态参数分布,由此分析了密度波不稳定发生的机理,并分析了质量流速、系统压力、入口过冷度对不稳定的影响。结果表明,与已有实验及理论结果相比,瞬态参数计算结果与实验结果符合较好,可较好找到不同工况下直管内气液两相流发生不稳定的边界,结果优于Khabenski线算图方法。
The secondary side of the nuclear power plant steam generator is working in a two-phase convective boiling process in which two-phase flow instability must be avoided in design . The time domain method was used to study the two-phase flow instability in a vertical up-flow tube . One-dimensional model was established and a numerical program was compiled .Two-phase flow density-wave instability was simulated ,and transient parameter distribution in the tube during the dynamic process was presented . The program was also used to analyze the effects of mass velocity ,system pressure ,and inlet sub-cooling on flow instability . T he result show s that the transient parameter distribution from the program agree well with the experimental results ,and it can predict the instability boundary ,w hich is more accurate than that of the usually used Khabenski nomographic method .

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在管内径9.0 mm、壁厚1.5 mm、螺旋管绕径283.0 mm的立式螺旋管内,对CO2流动沸腾换热特性进行实验研究。分析热流密度(q=1.4~48.0 kW/m2)、质量流速(G=54.0~400.0 kg/(m2·s))和运行压力(pin=5.6~7.0 MPa)对内壁温分布和换热特性的影响规律。结果表明:螺旋管内壁温周向分布不均匀,单相液体以及过热蒸汽区离心力的作用使内侧母线温度最高、外侧母线温度最低,在两相沸腾区蒸汽受到浮升力作用聚集在管上部而容易发生蒸干,因此上母线温度最高,温度最低值则由离心力和浮升力的相对大小共同决定。局部平均换热系数随热流密度以及进口压力的增加而显著增加,但增大质量流速对换热系数的影响不大,表明核态沸腾是CO2在螺旋管内流动沸腾的主要传热模式而强制对流效应较弱;发现了随着热流密度增加所引起的核态沸腾强度变化以及干涸和再润湿使得换热系数随干度的变化可分成3个区域。并基于实验获得的2 124个数据点拟合两相区沸腾换热关联式。
Within the ranges of pressure from 5.6 to 7.0 MPa, mass flux from 54.0 to 400.0 kg/(m2?s) and heat flux from 1.4 to 48.0 kW/m2, an experimental investigation was conducted on flow boiling heat transfer of CO2 through a helically coiled tube. The test helically coiled tube has an inner diameter of 9.0 mm, a wall thickness of 1.5 mm and a coil diameter of 283.0 mm. The effects of heat flux, mass flux and operating pressure on heat transfer coefficient and inner wall temperature distribution were discussed. The experimental results show that the inner wall temperature distributions along the circumference were non-uniform. For the sing-phase liquid flow and the superheated vapor flow, the inner wall temperature was highest in the inside and lowest in the outside, attributing to the centrifugal force. But in the two-phase area, the highest inner wall temperature appears at the top, which is because that the vapor phase gathers at the top due to the buoyancy force, tending to dry out. The l

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对国内外微通道流动和换热的研究实验作了总结，阐述了影响微通道换热系数的因素，如热流密度、过热度和干度等．对去离子水在内径为0．65 mm、长为102 mm 的圆形管道内流动沸腾换热进行了实验研究，得到了局部换热系数随干度的变化关系，进而根据换热系数的变化趋势讨论了饱和流动沸腾区微通道内主导的换热机制．结果表明：从换热系数随干度的变化关系很难判定主导的换热机制；将实验数据与已发表的预测关联式进行了比较，发现大多关联式都失效，说明基于常规理论的模型不再适用于微通道．
The studies of flow boiling heat transfer in a microchannel at home and abroad are summarized,as well as the factors that influence the heat transfer coefficient,such as heat flux density,degree of superheat and dryness.Experimental and theoretical analysis of flow boiling heat transfer in the microchannel with a diameter of 0.65 mm and a length of 102 mm were carried out to obtain the relationship between the local heat transfer coefficient and dryness.And the dominated heat transfer mechanism at saturated flow boiling region in the microchannel was discussed according to the variation of heat transfer coefficient.The results show that it is difficult to determine the dominated heat transfer mechanism from the relationship between heat transfer coefficient and dryness.The comparison between the experimental data and the published predictive correlations is made,and most of the correlations can’t predict the experimental data well.It is concluded that the models based on con

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