乙醇在改进型机加工多孔管上的池核沸腾换热研究

测试了乙醇在 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核沸腾传热系数 ,结果表明 ,JK- 2管比 JK- 1管能更有效地强化乙醇的池核沸腾传热。提出了一个新的池核沸腾强化传热机理 ,并导出相应的池核沸腾强化传热关联式 ,该关联式与实验数据吻合良好     

铝多孔表面换热管强化沸腾换热的研究及其工业应用

对铝多孔表面管的传热性能进行了研究。结果表明 ,铝多孔表面对强化液体沸腾换热有显著效果 ,沸腾传热膜系数比光滑管提高 5～ 6倍 ;由应用实验和工业数据获得的管外铝多孔表面沸腾传热膜系数关联式 ,计算误差小于± 1 2 %。对使用铝多孔表面管的经济效益进行了深入分析。     

水的池核沸腾强化传热

测试了水在9根第2代机械加工表面多孔管(JK-2管)、1根第1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核沸腾传热系数,结果表明,JK-2管比JK-1管能更有效地强化水的池核沸腾传热.提出了一个新的池核沸腾强化传热机理,并导出了相应的池核沸腾强化传热关联式,该关联式与实验数据吻合良好.     

影响换热器用多孔表面管沸腾换热的主要因素

综述了换热器用多孔表面管沸腾传热的各种影响因素,既介绍了如孔穴直径、多孔层厚度及孔隙率等多孔层的特征参数的特性;也介绍了材料物性、加工工艺、工质物性、压力与温度等对沸腾传热的影响.同时对各种因素对沸腾换热的具体影响进行了分析归纳,对今后多孔表面强化沸腾传热的研究提出了一些自己的建议.     

R134a在水平双侧强化管外沸腾换热

对氟里昂R134a在水平单管外的沸腾换热性能进行了试验研究,试验管为4根双侧强化管。在蒸发温度为8℃时比较不同肋型的强化换热性能。结果表明：所研究的强化管均有明显的强化换热作用,E12管的总传热系数略高于其他强化管,其管外沸腾传热系数相对于光管Cooper公式预测值的强化倍率为2.23～2.71,平均值为2.54。由于R22和R134a的物性不同,其管外沸腾传热系数约比R134a高出20%～40%。试验管的沸腾换热强化倍率与制冷剂的关系不明显。     

i影响换热器用多孔表面管沸腾换热的主要因素

综述了换热器用多孔表面管沸腾传热的各种影响因素,既介绍了如孔穴直径、多孔层厚度及孔隙率等多孔层的特征参数的特性;也介绍了材料物性、加工工艺、工质物性、压力与温度等对沸腾传热的影响。同时对各种因素对沸腾换热的具体影响进行了分析归纳,对今后多孔表面强化沸腾传热的研究提出了一些自己的建议。     

有肋隧道机加工表面多孔管沸腾传热性能和机理的探讨

一、前言在化工,制冷,空调等行业,往往由于蒸发器沸腾一侧给热系数较小,成为传热的主要热阻。寻求高效的沸腾传热元件来强化沸腾传热,是当前研究的一个重要课题。七十年代以来,先后研制出了机械加工表面多孔管,     

肋形隧道表面多孔管强化沸腾传热的研究

本文报道了肋形隧道机械加工表面多孔管(JK-2管)单管管外池沸腾实验。实验工质为R-113和R-11。实验结果表明:对R-113和R-11工质,JK-2管沸腾给热系数分别比光滑管高2.5～15倍及1～10倍,比JK-1管高20％～150％,而且,当工质为R-113时,JK-2管比光滑管的临界热负荷高约100％。并建立了一个池沸腾膜传热系数的准数关联式,其预测值和实验值的相对误差在±15％以内。     

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。     

多孔表面强化沸腾传热的研究进展

本文综述了多孔表面用于强化沸腾传热的研究工作。即介绍了多孔表面的形成和结构表征方法、多孔表面的沸腾传热性能以及描述多孔表面沸腾传热机理的物理和数学模型，同时分析了影响多孔表面沸腾传热性能的因素，探讨了多孔表面强化沸腾传热研究的发展方向。     

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.     

An Experimental Study of Porous Surface Tubes for Enhancement of Binary Liquid Mixture Pool Boiling Heat Transfer

Experiments have been conducted on the pool boiling of binary mixtures in JK tubeswith porous surface and ribbed channels,attempting to enhace the boiling heat transfer coefficientsinvolved.The binary mixtures used in this study are R113 and R11.The results show that the boilingfi1m heat transfer coefficients for the R113 and R11 binary mixtures in JK2 and JK1 tubes are 2—8tirnes and 2—5 times greater than those in smooth tubes respectively.Based on this experimentaldata and simple theoretical analysis,a correlation has been proposed to predict the boiling heattransfer coefficients for R113/R11 mixtures in a horizontal JK tube with a relative error of less than16%.     

池式核沸腾中的“界面汽化热阱”效应

采用扩散极限电流技术 ( LDCT)与传热测定同时进行的实验方法分析了池核沸腾中的“界面汽化热阱”效应。传热实验所测定的是池核沸腾的总换热系数 ,由 LDCT测定并以类比原理可以获得对流传热系数 ,两者差值即为“界面汽化热阱”效应。实验结果表明 ,沸腾时 ,“界面汽化热阱”效应随热流率的提高而显著增大。对以 LDCT法测得的对流传热数据进行关联 ,获得了准数式。     

低压条件下纳米流体的沸腾换热特性

在不同低压压力和不同纳米流体浓度下对光滑传热面上的水基纳米流体的池内沸腾特性进行了试验研究.纳米流体由平均直径50 nm的氧化铜粒子加入去离子水中组成,没有加入任何添加剂.研究主要针对7.2 kPa到100kPa的压力区间和0.1%到2%的质量浓度区间内压力和颗粒浓度对光滑表面沸腾换热特性的影响,研究结果表明:压力对纳米流体的沸腾换热特性有强烈影响,沸腾换热系数和临界热流密度(CHF)强化率随着压力的降低而大幅度增加.纳米流体浓度对沸腾换热系数和临界热流密度(CHF)有重要影响,并且在质量浓度约1%附近存在一个最佳颗粒浓度.研究结果显示由与去离子水相比,质量分数为1%,压力为7.2 kPa的纳米流体在光滑表面上的沸腾换热系数和临界热流密度都得到了显著提高.     

换热器用多孔管沸腾传热物理模型比较

综述了针对多孔管沸腾传热的物理模型.分析了影响多孔表面沸腾传热的影响因素,对各种模型的优缺点进行了分析归纳,探讨了多孔管沸腾传热物理模型研究的发展方向,对今后的发展提出了自己的建议.     

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。     

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.     

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.