共查询到20条相似文献,搜索用时 765 毫秒
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对表面活性剂SDS、CTAB、Triton X-114和Triton X-100水溶液物性及其池核沸腾传热进行了试验,重点探讨了表面活性剂分子结构参数和溶液物性对沸腾传热的影响。结果表明:表面活性剂溶液沸腾传热效果、表面活性剂相对分子质量对表面活性剂溶液沸腾传热的影响规律都与表面活性剂的电离特性密切相关,离子型表面活性剂SDS与CTAB溶液的沸腾传热系数比值与相对分子质量的比值成-0.22的指数关系,而非离子表面活性剂Triton X-114和Triton X-100溶液不存在指数关系。动态表面张力和热流密度相等时,SDS和CTAB溶液沸腾传热特性差异主要受相对分子质量和平衡接触角的影响,而Triton X-100和Triton X-114溶液则受质量分数、EO基团数、浊点和动力黏度的综合作用。 相似文献
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Suspended nanoparticles inside the nanofluids can modify the characteristics of heated surfaces and the physical properties of the base liquids, offering a great opportunity to optimize boiling heat transfer. This paper reviews the mechanisms of nanoparticle deposition and the effects induced by deposited nanoparticles on surface roughness, force balance at the triple line, surface wettability, active nucleation site density, receding and advancing contact angles, boiling heat transfer coefficient and critical heat flux. Both enhancement and deterioration effects on boiling heat transfer coefficient and critical heat flux have been discussed. Most of the existing experimental data confirms the enhancement of critical heat flux using alumina nanofluid, however there is no consistency about its boiling heat transfer coefficient. 相似文献
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A model of evaluation and prediction of enhancement of boiling heat transfer with additives has been proposed according to fuzzy fundamentals. Correlative appraisement of boiling heat transfer augmentation was done with the model based on 39 additives which were tested by the authors and other researchers. The results show that the evaluation of 35 additives is consistent with experiments, which means that the accuracy of the model is 89.7 percent. In addition, the prediction of the ability of boiling heat transfer enhancement with sodium oleate, polyethylene glycol and Tween-40 is also in good agreement with correspondent experiments. 相似文献
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引 言流动沸腾传热广泛存在于石油、化工、轻工、动力及能源等各个领域 ,但三相流动沸腾传热的研究极少 .李修伦等[1]在流动沸腾系统中加入惰性固体粒子 ,进行了汽 -液 -固三相流沸腾传热的初步研究 .李修伦、闻建平[2 ,3]进一步将三相流和沸腾换热相结合 ,较好地解决了沸腾传热强化和防垢、除垢问题 .李修伦、张利斌等[4 ]又采用循环流化床技术 ,结合粒子在沸腾系统中的强化特性 ,开发了汽 -液 -固三相循环流化床蒸发器 ,它具有良好的强化传热和防、除垢性能 .上述研究均属于单组分三相流动沸腾传热 ,而关于二元物系三相流动沸腾传热的研… 相似文献
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本文以不定常传热理论为基础,对槽道表面沸腾传热进行了理论分析研究。分析了气泡的生长规律,建立了气泡壁面微层液膜的流动和传热的物理和数学模型,并与气泡顶部液体的不定常传热联系起来,得到了气泡生长和传热关系式。并且由几个约束性条件,对槽道的几何尺寸进行了判定,提出了适用的槽深和槽宽的变化范围,可供设计时参考。利用本文的关系式,对水蒸气和氟致冷剂(CFC)进行了数值计算,并与实验结果进行比较,两者基本一致。 相似文献
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以Tween20、Span20及两者复配物为表面活性剂,实验研究了其对水过冷池沸腾传热特性影响。基于实验结果与表面张力、接触角、临界胶束浓度等基础物性分析发现,单一表面活性剂对沸腾传热的影响由其添加种类、浓度及热通量共同决定。一方面,不同于饱和沸腾情形,过冷状态下Tween20能够有效降低沸腾起始点温度与壁面过热度,但其沸腾强化效果在高热通量下减弱;另一方面,Span20只在低浓度下表现出强化效果,其浓度增大将引起壁面过热度大幅攀升。此外,尽管Tween20与Span20都具有强化沸腾传热的潜力,但两者复配表面活性剂在实验研究浓度范围内均恶化了沸腾传热过程。研究结果可为传热强化复合工质过冷池沸腾传热特性分析提供基础依据,并为其配制提供指导。 相似文献
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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. 相似文献
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There has been increasing interest of late in nanofluid boiling and its use in heat transfer enhancement. This article covers
recent advances in the last decade by researchers in both pool boiling and convective boiling applications, with nanofluids
as the working fluid. The available data in the literature is reviewed in terms of enhancements, and degradations in the nucleate
boiling heat transfer and critical heat flux. Conflicting data have been presented in the literature on the effect that nanofluids
have on the boiling heat-transfer coefficient; however, almost all researchers have noted an enhancement in the critical heat
flux during nanofluid boiling. Several researchers have observed nanoparticle deposition at the heater surface, which they
have related back to the critical heat flux enhancement. 相似文献
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Based on the tests of more than ten different additives, several effective additives are found capable of improving the boiling heat transfer behavior of water pronouncedly. The mechanism of the enhancement of nucleate boiling with additives has been investigated, and the results indicate that one of the important reasons is that the nucleation sites have been increased. 相似文献
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纳米流体沸腾传热研究进展 总被引:1,自引:0,他引:1
介绍了纳米流体沸腾传热的最新研究,从纳米流体特性和沸腾表面特性两个方面阐述纳米流体沸腾传热的作用机制,指明纳米颗粒和沸腾表面特性以及两者之间的交互关系是目前研究结果存在分歧的主要原因。对纳米颗粒在制冷系统中的应用基础研究进行了展望,并指明了纳米流体沸腾传热的研究方向。 相似文献
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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。 相似文献