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《工程热物理学报》2021,42(6):1553-1560
本文针对0.15 MPa、0.2 MPa以及0.3 MPa三个压力下甲烷的池内核态沸腾进行了系统实验研究,得到了相应的甲烷核态沸腾传热数据,并将实验结果和现有的核态沸腾传热关联式进行对比,分析各个关联式对甲烷沸腾数据的拟合偏差和影响因素,结果表明McNelly和Labuntsov关联式的拟合结果最好,偏差均在5%以内。同时所有由制冷剂数据得到的沸腾关联式均可较好的拟合出甲烷沸腾换热系数的变化趋势,除Nishikawa关联式外其余偏差均小于30%,而对于Nishikawa关联式,仅仅改变其常数项即可得到较好的拟合结果。从传热关联式的拟合情况来看,甲烷与常规制冷剂的沸腾传热特性没有本质差异。 相似文献
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给出了在低热流密度下沸腾-凝结面间距(相变腔高度)对沸腾凝结共存相变传热规律影响的实验研究结果。沸腾工质为去离子水,相变腔由水平朝上且具有薄膜延展面的紫铜沸腾面、抛光且朝下的冷凝面以及玻璃管侧壁面组成。高度为48 mm的相变腔对应充液高度分别为10 mm、14 mm、18 mm、22 mm、26 mm、30 mm和34 mm;高度为18 mm的相变腔对应充液高度分别为6 mm、8 mm、10 mm和12 mm。实验观察和测试结果表明,在所给定的有限空间范围内沸腾和凝结之间存在明显的相互作用,沸腾和凝结之间的这种相互作用及程度是引起传热变化的主要原因。随着液面高度的增加,沸腾和凝结表面传热系数均先增加后减小,同时,在本文研究所涉及的范围内,均存在一个使沸腾和凝结表面传热系数最大的充液高度,这说明沸腾-凝结面距离对沸腾凝结共存相变传热规律的影响具有一定的普遍性。 相似文献
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The nucleate pool boiling heat transfer data on a smooth flat surface were measured for three binary mixtures of HC600a/HFC134a, HC600a/HC290, and HC600a/HFC23. Much effort was made to investigate the influence of the boiling range on the pool-boiling heat transfer performance. From the experimental results, the HC600a/HFC23 mixture with a wide boiling range showed lower heat transfer coefficients (HTCs) than the mixture with a narrow boiling range such as HC600a/HFC134a and HC600a/HC290 systems. The measured data were also compared with the results predicted by five well-known correlations. It can be found that the average deviation is less than 25% for mixtures with narrow boiling ranges, but a larger deviation for mixtures with wide boiling ranges. 相似文献
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表面活性剂对池沸腾换热的影响 总被引:1,自引:0,他引:1
本文以SDS(十二烷基硫酸钠)为表面活性剂,研究了在不同过冷度下SDS浓度对池沸腾换热的影响.结果表明在低SDS浓度下,沸腾换热在一定热流密度范围内得到显著强化.在不同过冷度下.均存在相应的最佳SDS浓度值,最大换热系数可达纯水的2~4倍.在饱和沸腾状态下,临界热流密度(CHF)随SDS浓度的增加而减小,沸腾曲线呈现三类分歧,且存在"S"型沸腾曲线及较明显的沸腾滞后现象. 相似文献
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Abstract A pool boiling experiment with either water or Freon-113 was conducted to investigate nucleate boiling from a heated wall with either a spherical or a cylindrical attachment. The result revealed that nucleate boiling can be enhanced by applying a horizontal cylindrical attachment to a vertical heated wall, owing to the favorable thermal environment characterized by a small-gradient liquid temperature profile within the restricted regions between the attachment and the heated wait. Nucleate boiling is enhanced in terms of a lower wall superheat required for incipient boiling and more bubbles generated than from an open heated wall. As a result of the enhanced nucleate boiling, heal transfer of the vertical heated wall above the attachment was improved due to excessive bubbles moving upward along the heated wall, causing removal of the thermal layer near the wall and evaporation of the thin liquid film between the bubbles and the wall. The boiling curve hysteresis with Freon-113 was significantly reduced as a result. The effects of diameter, length and surface roughness of the cylindrical attachment were also investigated. 相似文献
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本文利用动态微液层模型对双组分混合物的沸腾换热现象进行了理论预测。本模型认为沸腾换热的机理主要是由于在气泡的周期生长过程中所形成微液层的蒸发。模型中考虑了气泡生长过程中液体传质的影响,给出了气泡生长过程中传热面上气-液-固接触的动态构造,计算结果与实验结果能够较好的符合。 相似文献
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This article deals with an experimental study of the influence of a DC uniform electric field on the nucleate boiling heat transfer. Electrohydrodynamic (EHD) effects on heat transfer coefficients for dielectric liquids are quantitatively investigated by performing experiments on various liquids with different properties. In these experiments, n-pentane, R-113, and R-123 are used as working fluids and the boiling phenomenon takes place on a horizontal plane copper surface. The experimental results have shown: (1) a threefold increase of nucleate pool boiling heat transfer coefficients, (2) a threefold increase of the critical heat flux (CHF), and (3) the disappearance of the hysteresis phenomenon. For nucleate pool boiling and CHF regimes, heat transfer laws based on dimensionless numbers are proposed. The results obtained by the proposed EHD model are in good agreement with the experimental results. 相似文献