共查询到20条相似文献，搜索用时 750 毫秒
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提出了临界热流密度的一个分形模型,根据加热表面活化点的分形分布得到了临界热流密度的表达式,从该模型中发现大空间临界热流密度(CHF)是壁面过热度、接触角和流体物理特性的函数。接触角对临界热流密度有重要的影响。沸腾表面模型预测的结果与实验数据进行了比较,两者是极好的吻合。 相似文献
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张燕 《上海大学学报(英文版)》2006,10(3):279-280
The objective of this dissertationis toinvestigate thei mpingingjet under the influence of crossflow.It hasbeen known that there exist jet shear layer ,i mpinge-ment on the bottom wall ,interactions between the in-duced wall jet and the ambient crossflowin near field .There are fewintensive studies of the i mpinging jet incrossflowat home and abroad due to the complexitiesof flow, such as the formation and evolution of thevortical structures ,interactions among vortices , whileresearches on th… 相似文献
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针对废弃热量利用率低的问题,深入研究喷射制冷循环系统的工作原理和主要的内部结构,对喷射制冷循环系统的工作过程进行建模分析,得出系统中主要工作参数之间的数学关系。然后引入蒸汽压缩制冷原理,设计一个增压喷射制冷循环系统,对系统的性能特点进行详细分析,并给出在不同现实需求下的改进优化策略。测试结果表明设计的增压喷射制冷循环系统可以提高低品味的热量的利用率。 相似文献
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建立了模拟逆流降膜除湿过程传热传质的数学模型,给出了传热传质的控制方程和适当的边界条件和气液界面条件.采用氯化钙作为除湿剂,运用控制容积法对降膜除湿溶液与被处理空气之间的除湿过程进行了分析和计算.获得了相应的除湿溶液与被处理空气的速度场、温度分布和出口参数.计算结果表明:沿着除湿器高度方向溶液和空气的温度、溶液的浓度、空气的湿度在入口区域变化较快而在出口区域变化较慢.可分别通过增加竖壁的高度、溶液的入口浓度和溶液的流速来改善除湿过程;同样,也可通过降低空气的流速或空气入口湿度达到改善除湿过程的目的.研究结果有利于改进除湿器的性能,为太阳能液体除湿、空调系统的优化设计和运行调节提供了理论依据. 相似文献
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Gas-liquid two-phase flow and heat transfer can be encountered in numerous fields, such as chemical engineering, refrigeration, nuclear power reactor, metallurgical industry, spaceflight. Its critical heat flux (CHF) is one of the most important factors for the system security of engineering applications. Since annular flow is the most common flow pattern in gas-liquid two-phase flow, predicting CHF of annular two-phase flow is more significant. Many studies have shown that the liquid film dryout model is successful for that prediction, and determining the following parameters will exert predominant effects on the accuracy of this model: onset of annular flow, inception criterion for droplets entrainment, entrainment fraction, droplets deposi-tion and entrainment rates. The main theoretical results achieved on the above five parameters are reviewed; also, limitations in the existing studies and problems for further research are discussed. 相似文献
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Gas-liquid two-phase flow and heat transfer can be encountered in numerous fields, such as chemical engineering, refrigeration, nuclear power reactor, metallurgical industry, spaceflight. Its critical heat flux （CHF） is one of the most important factors for the system security of engineering applications. Since annular flow is the most common flow pattern in gas-liquid two-phase flow, predicting CHF of annular two-phase flow is more significant. Many studies have shown that the liquid film dryout model is successful for that prediction, and determining the following parameters will exert predominant effects on the accuracy of this model： onset of annular flow, inception criterion for droplets entrainment, entrainment fraction, droplets deposition and entrainment rates. The main theoretical results achieved on the above five parameters are reviewed; also, limitations in the existing studies and problems for further research are discussed. 相似文献
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Micro-pin-fin cooler mounted on the power chip enables the heat removal to meet modern microsystem requirement. Carbon nanotubes
(CNTs) have been proven as a potential material for micro-coolers due to the superior thermal conductivity, good mechanical
property and so forth, and there appear various applications of CNTs in the micro-cooler technology. In the present paper,
an analysis of the thermal and hydraulic characteristics of the micro-pin-fin heat sink was conducted, where air was used
as the cooling medium and an impinging jet was introduced to enhance the heat transfer. Three-dimension computational fluid
dynamics (CFD) simulations were carried out for micro-pin-fin coolers with various parameters, including the pin-fin size
and pattern as well as the jet velocity and nozzle diameter. The flow field and thermal properties of the micro-pin-fin heat
sink were obtained, and the heat removal efficiency was evaluated. 相似文献
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通过记录液-液体系中射流断裂形成液滴的过程,分析了孔径、流速对液滴粒径的影响,得出结论,孔径越大形成的液滴平均粒径越大,液滴粒径随流速的增加先减小后增大。 相似文献
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Ze-wei Tao Long-gui Li Zhao-hua Geng Tao Dang Shan-jun Zhu 《Journal of Zhejiang University. Science. B》2010,11(4):238-248
Therapeutically delivered mesenchymal stem cells (MSCs) improve ventricular remodeling. However,the mechanism underlying MSC cardiac remodeling has not been clearly determined. Congestive heart failure (CHF) was induced in rats by cauterization of the left ventricular free wall. MSCs were cultured from autologous bone marrow and injected into the border zone and the remote myocardium 5 d after injury. Ten weeks later,when compared with sham operation,CHF significantly increased nucleus mitotic index,capilla... 相似文献
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基于加热表面核化点遵循泊松与分形分布,提出了临界热流密度的一个数学模型,从该模型中发现大空间临界热流密度(CHF)是壁面过热度、接触角和流体物理特性的函数.对不同的接触角,模型预测的结果与实验数据进行了比较.两者很好地吻合. 相似文献
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朱海燕 《泰州职业技术学院学报》2010,10(3):29-30,59
目的观察慢性充血性心力衰竭（CHF）患者的血胰岛素和糖代谢变化,并探讨依那普利对CHF患者胰岛素敏感性的影响。方法CHF患者69例,依那普利（n=37）（第一周10mg,1次／d,后三周20mg,1次／d）和地高辛（n=32）（第一周0．25mg,1次／d,后三周0．125mg,1次／d）,治疗前和治疗4周后检测空腹血糖（FPG）、空腹血清胰岛素（FINS）和空腹血清C肽（CP）水平,并计算出FPG／FINS比值、胰岛素敏感性指数IAI值[IAI=－ln（FPG×FINS）]作为机体胰岛素敏感性评价指标,分别比较两组患者治疗前后的胰岛素敏感性变化。结果治疗4周后,依那普利组CHF患者的胰岛素敏感性显著增加,而地高辛组患者胰岛素敏感性无显著变化。结论依那普利有改善CHF患者IR的作用。 相似文献
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为研究微小孔径气体受限冲击射流的换热特性,采用电阻丝加热方形酚醛树脂薄板作为模拟发热芯片的换热表面,沿对角线均匀布置热电偶以采集表面温度分布。以3mm孔径的圆形单孔及1mm孔径两种不同排列的圆形多孔喷射板对发热面进行中低Re数的射流冲击换热实验．通过改变风数及高度孔径比等参数得到了批数的径向分布及驻点区的换热特性,为射流冲击换热在封装芯片冷却上的应用提供了实验基础。 相似文献
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针对三套加氢精制装置用能存在的不足,采取了装置间热联合、优化改进换热网络、充分利用低温热等措施。实现汽油加氢、航煤加氢两套装置的热量集成,汽油加氢的富余高温位热量正好用于航煤加氢装置高温位热量需求,柴油加氢装置低温热也得到了更有效的利用。三套装置经节能改进后,年节约能量488．893 MJ ,节能效果显著。 相似文献
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聚能射流形成的数值模拟,涉及到大变形、高应变率以及材料的破坏,传统的拉格朗日或欧拉方法在解决该问题均有很大的局限性,先后发展了网格重分、ALE、SPH等方法,以及界面处理技术,各有所长,但尚未完全解决,而在实际工作中,切合实际的药型罩介质本构关系则是聚能射流数值模拟的关键,高效并行计算与可视化则是聚能射流数值模拟的必由之路,并阐述了聚能射流数值模拟的发展趋势． 相似文献
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Numerical study of heat transfer characteristics of downward supercritical kerosene flow inside circular tubes 总被引：3，自引：0，他引：3
The heat transfer characteristics of China RP-3 aviation kerosene flowing in a vertical downward tube with an inner diameter of 4 mm under supercritical pressures are numerically studied. A ten-species surrogate model is used to calculate the thermophysical properties of kerosene and the re-normalization group (RNG) k-ε turbulent model with the enhanced wall treatment is adopted to consider the turbulent effect. The effects of mass flow rate, wall heat flux, inlet temperature, and pressure on heat transfer are investigated. The numerical results show that three types of heat transfer deterioration exist for the aviation kerosene flow. The first type of deterioration occurred at the tube inlet region and is caused by the development of the thermal boundary layer, while the other two types are observed when the inner wall temperature or the bulk fuel temperature approaches the pseudo-critical temperature. The heat transfer coefficient increases with the increasing mass flow rate and the decreasing wall heat flux, while the inlet bulk fluid temperature only influences the starting point of the heat transfer coefficient curve plotted against the bulk fluid temperature. The increase of inlet pressure can effectively eliminate the deterioration due to the small variations of properties near the pseudo-critical point at relatively high pressure. The numerical heat transfer coefficients fit well with the empirical correlations, especially at higher pressures (about 5 MPa). 相似文献
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YANG Ying TONG Mingwei WU Zhijuan College of Power Engineering Chongqing University Chongqing P. R. China 《重庆大学学报(英文版)》2004,3(1):6-10
1.IntroductionTherequirementsforenvironmentalprotectionaregettingstricterworldwide.Notonlythenaturalecologyandresourcesshouldbeconsideredinconservation,butalsotheenvironmentbeprotectedfrombeingsacrificedastheexpenseofproductivityboosts.Aconventionalmachiningprocessusedtotakeoilasthelubricantandcoolantforthesurfacesofmachinedtoolsandworkpieces,whichbroughtforthenvironmentpollution,andincreasedcostsonpost-treatingoftools,workpiecesandcuttingscrap.Asaresult,greenmachiningtechnologyfeaturingcleanp… 相似文献