通气环套内垂直圆柱表面核沸腾传热研究

研究了带有同心套管的垂直圆柱形加热表面在环隙中通入空气时的核沸腾传热性能。结果表明，通入空气使沸腾传热系数有所提高，并且加热表面温度有所降低。通入空气也会增强自然对流传热，而且这种增强幅度比沸腾时更大。在实验条件下，通气可使沸腾传热系数提高39．63％-80．50％，壁面温度可降低1．39-2．58℃，自然对流时通气可提高传热系数380．09％-482．52％。为此对上述实验结果用扰动增强和“界面汽化热阱”效应增强的机理来进行了分析。实验还在恒定热流率下考察了气速对沸腾传热系数的影响。结果表明，沸腾传热系数随气速提高先增加后降低。用Mashima和Ishii的两相流模型进行了计算，结果说明了这种气速影响的原因是由于由泡状流向弹状流流型的转变。     

流动沸腾核态抑制的实验研究

通过对水在垂直矩形通道内的流动沸腾实验,研究了流动沸腾核态抑制的规律,确定了不同流动沸腾区域的分布。沸腾抑制点参数,可以用空穴最大和最小半径的比值表示(rmax/rmin)sup,描述不同的流动沸腾状态。当最大空穴半径趋近于最小空穴半径时,活化核心密度减小,核态沸腾受到抑制。最大空穴半径的变化是决定流动沸腾抑制点参数的主因。流动沸腾的3个状态分布如下:(rmax/rmin)sup<40,对流沸腾状态;40≤(rmax/rmin)sup≤120,不确定状态;(rmax/rmin)sup>120,核态沸腾状态。     

基于气泡动力学分段调控浸润性强化核态沸腾

基于多孔或微结构表面润湿性改性的核态沸腾强化传热,已得到广泛研究。利用CFD-VOF数值模拟方法,针对单晶硅微柱表面单气泡的生长及脱离过程,进行表面浸润性分段调控,实现气泡沸腾换热的全程强化。分别调控初始接触角为48°、60°、90°和110°后,同一时刻 （t = 0.152 ms） 变接触角为20°,对比研究分段调控浸润性对气泡动力学过程与表面换热性能的影响。结果表明：疏水性可提高气泡生长速率,增强微柱表面对气泡的黏附力,促进气泡在微结构缝隙内的横向铺展;t = 0.150 ms时接触角为110° 表面上气泡与底面接触面积增加1.3倍,微层蒸发功率增加1.2倍。需要指出的是,毛细效应随颗粒粒径变化趋势受到多孔介质复杂孔隙结构特征的影响。在当前粒径范围内,认为其具有正相关关系,但在更大范围内的对应关系,还需要在未来进一步深入揭示。     

微柱结构表面核态沸腾单气泡的数值模拟

利用计算流体力学方法（computational fluid dynamics, CFD）对三维均匀微柱结构表面单气泡核态沸腾过程进行数值模拟研究,使用VOF模型（volume of fluid model, VOF）在界面网格追踪加密的条件下精确捕捉气液界面,同时考虑气液界面和微层处的蒸发,准确获得三维微柱表面单气泡核态沸腾过程中的气泡动力学、温度演化和蒸发换热性能。结果表明,气泡脱离时间为1.79ms,体现了微柱结构促进气泡脱离的强化作用。通过气泡横向和纵向直径的变化准确表征了气泡在脱离过程中的变形过程,并模拟得到该过程流场热边界层及壁面温度的演变规律。同时,通过微层蒸发和气液交界面蒸发功率随时间变化的监测,指出气泡生长过程微层蒸发量占总蒸发量的52%;t=0.95ms后微层蒸发消失,气液界面蒸发维持相对稳定值（0.1~0.2W）直至气泡脱离。蒸发换热特性耦合气泡与壁面接触情况随时间的变化,揭示了单气泡核态沸腾过程蒸发换热机理的阶段性特征及时间分区,为在核态沸腾单个气泡生长脱离过程中更准确划分时间阶段、建立沸腾换热模型奠定基础,提供了参考。     

“泵阱”在MTO中的新应用

根据中煤榆林MTO产品气压缩机一段吸入罐易发生高液位联锁隐患,在MTO中引入泵阱解决该问题,并介绍泵阱工作原理及特点。     

复合多孔表面管竖直管束在液氮中的沸腾传热

复合Gewa-T多孔表面管是在机械加工Gewa-T表面上再覆盖一层烧结多孔层而形成的强化传热管,针对复合Gewa-T多孔表面管竖直单管和管束在液氮池中的核态沸腾进行了实验研究,通过改变管束管间距、热负荷等得到了不同情况下的管束沸腾传热特性.沸腾的最佳管间距与管外径比为1.2,此时管束沸腾特性优于单管.     

具有电介质核圆柱多孔介质微波冷冻干燥过程的双升华界面模型

建立了具有电介质核多孔介质微波冷冻干燥过程的耦合传热传质的数学模型,应用变时间步长的有限体积法对各控制方程进行数值求解.计算结果表明：（1）多孔介质内部存在着两个升华界面;（2）同无核相比,合理选用电介质核可大大缩短干燥时间;（3）在初始饱和度较低时（S₀=0.2）,有、无电介质核两种情况下所需干燥时间相差较大,仍可在物料中加入电介质核来加速干燥.     

加固混凝土构件用碳纤维增强胶粘材料中的界面效应

对建筑结构胶粘剂中加固混凝土构件用碳纤维增强胶粘材料中的部分界面效应对性能影响及改善方法作了简要综述。     

化工生产中的“界面”现象对工艺设备的影响

分析了化工生产过程设备、管道中存在的各种“界面”现象及其影响，并提出相应对策。     

LDCT及其在气液两相流传热研究中的应用

介绍了极限扩散电流技术(LDCT)的基本原理及其在气液两相流研究中的应用.该技术利用置于电解质溶液中的电极间处于扩散控制的氧化还原反应,直接测得液固传质系数,经三传类比,可获得单相液体与气液两相流传热的特性.由于LDCT电极可制成微小尺度,并可进行瞬时值的测量,故可进行传质与传热局部值与瞬时值的测量,在气液两相流这一复杂系统传递特性的深入研究中,可成为一个十分有用的测试技术.     

甲醇在改进型机加工多孔管上池核沸腾换热特性的研究

测度了甲醇在９根第二代机械加工表面多孔管（ＪＫ－２管）、１根第一代机械加工表面多孔管（ＪＫ－１管）和１根光滑管上的单管饱和池沸腾传热系数,结果表明,ＪＫ－２管比ＪＫ－１管能更有效地强化甲醇的池沸腾传热。提出了一个简化的池核沸腾强化传热机理,并导出了相应的池核沸腾强化的传热关联式,该关联式与实验数据吻合良好。     

内加热垂直环隙中引入惰性气体时的沸腾传热

In this paper, boiling heat transfer in a vertical annulus with inner side heated with and without air introduction is experimentally studied. Results show that boiling heat transfer is significantly enhanced by the introduction of air. When air is introduced into the liquid with a temperature below boiling point, the enhancement of heat transfer is also detected. It is concluded from the study that the heat transfer enhanced by introduction of inert gas is due to the liquid vaporization at the gas-llquid interface near the wall, which removes a large amount of latent heat and lowers the interfacial temperature considerably. Thus the gas-liquid interface acts as a “heat sink” and the heat transfer is augmented significantly.     

Boiling Heat Transfer Enhancement in a Vertical Annulus by Introduction of Air in Liquid Flow

In this paper, boiling heat transfer in a vertical annulus with inner side heated with and without air introduction is experimentally studied. Results show that boiling heat transfer is significantly enhanced by the introduction of air. When air is introduced into the liquid with a temperature below boiling point, the enhancement of heat transfer is also detected. It is concluded from the study that the heat transfer enhanced by introduction of inert gas is due to the liquid vaporization at the gas-liquid interface near the wall, which removes a large amount of latent heat and lowers the interfacial temperature considerably. Thus the gas-liquid interface acts as a "heat sink" and the heat transfer is augmented significantly.     

非极性有机物蒸发热与正常沸点的关联

通过对正烷烃蒸发热、正常沸点与碳数关系的研究,理论推导出蒸发热与正常沸点之间的关系,并拟合得一简单适用的公式:Hυ=23.234×BP1.21256+1502.13。应用于上百种常见非极性有机物,误差较小。     

三甘醇水溶液池沸腾传热

Boiling of water/triethyleneglycol (TEG) binary solution has a wide-ranging application in the gas processing engineering. Design, operation and optimization of the involved boilers require accurate prediction of boiling heat transfer coefficient between surface and solution. In this investigation, nucleate pool boiling heat transfer coef-ficient has been experimentally measured on a horizontal rod heater in water/TEG binary solutions in a wide range of concentrations and heat fluxes under ambient condition. The present experimental data are correlated using major existing correlations. In addition a correlation is presented for prediction of pool boiling heat transfer for the system in which the vapour pressure of one component is negligible. This model is based on the mass transfer rate equation for prediction of the concentration at the bubble vapor/liquid interface. Based on this prediction, the temperature of the interface and accordingly, the boiling heat transfer coefficient could be straightforwardly calculated from the known concentration at the interface. It is shown that this simple model has sufficient accuracy and is acceptable below the medium concentrations of TEG when the vapor equilibrium concentration of TEG is almost zero. The presented model excludes any tuning parameter and requires very few physical properties to apply.     

混合制冷工质R134a/R142b池核沸腾传热强化研究

混合制冷工质的传热性能差,使得其应用受到一定限制,而采用适当的强化传热技术可以大大提高混合制冷工质传热性能。实验的热流密度范围内,在相同的热流密度条件下,非共沸混合制冷剂Ｒ１３４ａ／Ｒ１４２ｂ在机械加工表面多孔管外沸腾传热膜系数是光滑管的１．７８～３．３３倍。     

固体颗粒对池沸腾换热表面上结垢影响的机理分析

报道了固体颗粒对池沸腾换热表面结垢特性影响的实验研究结果。沸腾工质为ＣａＳＯ４水溶液，换热表面材料为紫铜，固体颗粒是０．５～１ｍｍ的玻璃珠。实验结果表明，在平表面池沸腾条件下引入固体颗粒只能在较短的运行时间内起到强化换热的作用。当运行时间较长时，不仅不能强化换热，反而因结垢而使得换热恶化。     

A Composite Heat Transfer Model For Pool Boiling on a Horizontal Tube at Moderate Pressure

The present work is aimed at building a comprehensive heat transfer model for pool boiling on horizontal tubes combining sliding bubble mechanism with natural convection, microlayer evaporation and transient conduction during boundary layer reformation, to predict the boiling heat flux for a given wall superheat. The model has been compared to experimental results from literature for R134a and also to independent experiments conducted by the authors for water. Even with a number of simplified assumptions a reasonably good agreement has been observed between model and experiments in the low and medium heat flux region and moderate pressure.     

R134a和R142b在表面多孔螺旋扁管外的沸腾传热

The objective of this work was to investigate nucleate pool boiling heat transfer performance and mechanism of R134a and R142b on a twisted tube with machine processed porous surface （T-MPPS tube） as well as to determine its potential application to flooded refrigerant evaporators. In the experimental range, the boiling heat transfer coefficients of R134a on a T-MPPS tube were 1.8-2.0 times larger than those of R134a on a plain tube. In addition, the developed experimental correlations verified that the predictions of the heat transfer coefficients of boiling R134a and R142bon a T-MPPS tube at the experimental conditions were considerably accurate.