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以R600a压力式封闭系统喷雾冷却过程为研究对象,对其换热过程进行分析。对液滴撞击热面后的状态进行建模,分析了其运动状态。通过忽略液膜的对流换热,引入韦伯数来简化并修正雾滴与热源表面的对流换热系数关联式;借鉴二次成核理论,通过单位时间内,单位面积上覆盖的雾滴数量对核态沸腾换热系数关联式修正。通过上述分析,以对流换热和核态沸腾换热两种机理为中心,建立了新的换热系数关联式。通过与其他文献的关联式、实验测量值进行比较、不同工质进行比较、不同实验系统比较,发现该式预测值和实验测量值偏差在±20%以内,能够很好地预测压力式封闭系统喷雾冷却过程的换热系数。 相似文献
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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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纳米流体对流换热的实验研究 总被引:15,自引:3,他引:12
建立了测量纳米流体对流换热系数的实验系统,测量了不同粒子体积份额的水-Cu纳米流体在层流与湍流状态下的管内对流换热系数,实验结果表明,在液体中添加纳米粒子增大了液体的管内对流换热系数,粒子的体积份额是影响纳米流体对流换热系数的因素之一。综合考虑影响纳米流体对流换热的多种因素,提出了计算纳米流体对流换热系数的关联式。 相似文献
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S. J. Jeong 《实验传热》2013,26(3):257-265
Abstract Because carbon dioxide is ozone friendly and has negligible global warming potential, it has received renewed interest in recent years as an important alternative refrigerant. In this article, the heat transfer characteristics of a carbon dioxide-filled two-phase closed thermosyphon were investigated experimentally, and the empirical heat transfer correlations are reported. The heat transfer data were analyzed, and heat transfer coefficients were compared with conventional heat transfer correlations. The results represent that heat transfer correlation of the heated section can be expressed with Kutatelatze's correlation, and heat transfer coefficients of the condenser section are found to be in reasonable agreement with the Nusselt equation. 相似文献
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The paper is focused on the practical application of parallel computing techniques in uncertainty assessment in simulation of heat transfer, mechanical and some other problems related to deterministic analysis of NPP safety. A methodology is developed and implemented in VARIA computer code that performs simultaneous run of multiple simulations on a parallel computing system with further statistical analysis of the array of their results. The current version of the code allows automated preparation and execution of multivariate simulations of thermal and mechanical behavior of pressurized water reactor structures by best-estimate (BE) codes in the scope of NPP safety assessment under severe accident conditions. The number of simultaneously launched tasks is limited only by the computer cluster capacity. The VARIA code is verified on multivariate simulation with HEFEST code of thermal behavior of a core melt in the VVER-440 reactor vessel during a severe accident. The influence of the variation of input parameters (decay heat value and coefficients of the applied convective heat transfer model) on the simulation results is studied. It is concluded that the potential field of applying the program is beyond the scope of analyzing severe accidents at NPP and includes also software product quality assurance and analysis of uncertainties of obtained simulation results. 相似文献
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喷淋蒸发翅管式冷凝器传热传质研究 总被引:1,自引:0,他引:1
采用蒸发式冷凝器可以降低制冷装置不可逆传热损失,提高机组效率。该文提出在制冷装置中采用喷淋蒸发翅管式冷凝器,分析了喷淋蒸发翅管式冷凝器的传热过程,建立其传热传质数学模型和设计计算方法,简要分析了环境温湿度、管翅结构、风速、淋水量等一些主要因素对传热传质性能的影响,为该种冷凝器的设计和应用提供理论参考。 相似文献
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Lei Zhang Junwei Wang Ran Liu Guohua Li Xiao Han Zhiqiang Zhang Jiayi Zhao Baomin Dai 《Entropy (Basel, Switzerland)》2022,24(7)
Heat transfer and frictional performance at the air-side is predominant for the application and optimization of finned tube heat exchangers. For aerospace engineering, the heat exchanger operates under negative pressure, whereas the general prediction models of convective heat transfer coefficient and pressure penalty for this scenario are rarely reported. In the current study, a numerical model is developed to determine the air-side heat transfer and frictional performance. The influence of air pressure (absolute pressure) is discussed in detail, and the entropy generation considering the effect of heat transfer and pressure drop are analyzed. Furthermore, prediction models of air-side thermal and frictional factors are also developed. The results indicate that both the convective heat transfer coefficient and pressure penalty decrease significantly with decreasing air pressure, and the air-side heat transfer coefficient is decreased by 64.6~73.3% at an air pressure of 25 kPa compared with normal environment pressure. The entropy generation by temperature difference accounts for the highest proportion of the total entropy generation. The prediction correlations of Colburn j-factor and friction factor f show satisfactory accuracy with the absolute mean deviations of 7.48% and 9.42%, respectively. This study can provide a reference for the practical application of fined tube heat exchangers under a negative pressure environment. 相似文献