共查询到18条相似文献,搜索用时 250 毫秒
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以计算流体力学(CFD)商业软件CFX为计算平台,对圆环通道内超临界水(SCW)的传热特性进行数值模拟。通过对几种湍流模型的对比,选取对超临界条件适用性相对较好的SST模型进行计算;比较光滑圆环通道与带肋片圆环通道内的壁温分布及传热系数的变化;研究肋片形状、高度、间距及宽度等因素对传热特性的影响。结果表明:圆环通道内肋片的存在会导致局部传热强化;在本文计算的尺寸范围内,肋片形状和宽度对传热的影响很小;一定范围内,增加肋片高度以及减小肋片间距都有利于传热强化。 相似文献
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强化单相流体管内强制对流换热的有效措施之一是使流体发生旋转运动。本文采用计算流体动力学(CFD)方法,参考已有实验研究,建立起带螺旋肋片圆环通道的流固耦合模型,对该通道内超临界水传热特性进行数值模拟。计算中选取与实验数据吻合较好的湍流模型,研究螺旋肋片对超临界水传热特性的影响。结果表明:螺旋肋片的存在会使通道内表现出传热增强,然而在正常传热工况下,这种强化传热的效果并不明显。螺旋肋片的个数和螺距对传热特性有很大的影响,实际中应予以考虑。此外,热工参数的变化会显著影响肋片两侧局部热点的温升和温度的周向不均匀性。 相似文献
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简单通道内超临界水传热特性实验研究 总被引:1,自引:1,他引:0
针对各国超临界水冷堆燃料组件设计方案,选取圆管、圆环形通道、方环形通道3种具有热工水力代表性的简单通道,开展超临界条件下水工质的传热特性实验研究。实验结果表明,热流密度、质量流速和压力3种热工参数对不同简单通道传热特性的影响趋势基本一致;在相同质量流速和压力下,换热系数在靠近拟临界温度处存在峰值,且随热流密度的增大而减小;在相同热流密度和压力下,相同主流体焓处对应的换热系数随着质量流速增加而增加;压力对超临界水传热特性影响较弱,仅在拟临界区域内换热系数峰值稍有不同;实验中出现了拟临界区域的传热恶化现象,传热恶化发生时壁温出现局部峰值。 相似文献
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Yoon Y. Bae 《Nuclear Engineering and Design》2011,241(8):3164-3177
This paper addresses three main subjects in supercritical heat transfer: (1) difference in thermal characteristics between upward and downward flows; (2) effect of simulating flow channel shape; (3) evaluation of the existing supercritical heat transfer correlations. To achieve the objectives, a series of experiments was carried out with CO2 flowing upward and downward in a circular tube with an inner diameter of 4.57 mm and an annular channel created between a tube with an inner diameter of 10 mm and a heater rod with an outer diameter of 8 mm. The working fluid, CO2, has been regarded as an appropriate modeling fluid for water, primarily because of their similarity in property variations against reduced temperatures. The mass flux ranged from 400 to 1200 kg/m2 s. The heat flux was varied between 30 and 140 kW/m2 so that the pseudo-critical point was located in the middle of the heated section at a given mass flux. The measurements were made at a pressure of 8.12 MPa, which corresponds to 110% of the critical pressure of CO2. The difference between the upward and downward flows was observed clearly. The heat transfer deterioration was observed in the downward flow through an annular subchannel over the region beyond the critical point. Several well-known correlations were evaluated against the experimental data, and new correlations were suggested for both a tube and an annular channel. 相似文献
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两流程2×2棒束超临界水传热实验研究 总被引:1,自引:0,他引:1
为支持欧盟2×2燃料组件入堆考核实验,开展了2×2棒束内超临界水传热实验研究。设计了两流程实验段,两流程之间通过矩形金属框隔离。2×2加热棒束通过定位格架安装在金属框中,超临界水通过第1流程向下流动然后进入第2流程冷却加热棒,第1流程通过金属框吸收第2流程流体的热量而温度升高。在2×2棒束横截面上存在明显的周向温度分布不均匀性。系统分析了实验参数包括质量流速、热流密度和实验压力对棒束平均换热系数的影响。结果表明,系统参数对棒束传热的影响规律与对单管和环管的一致。 相似文献
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Within the range of pressure from 9 to 30 MPa, mass velocity from 600 to 1200 kg/(m2 s), and heat flux at inner wall from 200 to 600 kW/m2, experiments have been performed to investigate the heat transfer characteristics of steam-water two-phase flow in vertical upward tube. The outer diameter of the tube is 32 mm, and the wall thickness is 3 mm. Based on results, it was found that Dryout is the main mechanism of the heat transfer deterioration in the sub-critical pressure region. Near the critical pressure, when the heat transfer deterioration occurs, the steam quality of water is lower than that in the sub-critical pressure region, so that DNB is the main mechanism in this pressure region. At supercritical pressure, the heat transfer performance in circular channel is improved and enhanced. Heat transfer deterioration phenomenon is observed when the fluid bulk temperature approaches to the pseudo-critical value. Nusselt correlation of the forced-convection heat transfer in supercritical pressure region has been provided, which can be used to predict heat transfer coefficient of the vertical upward flow in tube. 相似文献
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针对带定位格架的超临界水冷堆堆芯垂直上升类三角形子通道,开展超临界水的流动传热试验研究。反应堆堆芯类三角形子通道棒束直径为8 mm、栅距比为1.4,试验参数范围为:热流密度q=200~600 kW/m2、压力P=23~28 MPa、质量流速G=700~1300 kg/(m2·s)。分析了热流密度、压力和质量流速等热工参数对超临界水传热特性的影响。试验结果表明:定位格架处质量流速升高,流体扰动性增强,换热系数提升显著;在超临界压力下,提高压力会导致内壁温度上升,换热系数峰值降低;过高的热流密度会导致换热系数峰值降低,适当减小热流密度可提高换热性能;提高质量流速会导致内壁温度降低,换热系数峰值上升,能够显著提高换热性能。压力变化对定位格架区域传热特性影响较小,适当提升压力可提高系统安全性。 相似文献
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《Journal of Nuclear Science and Technology》2013,50(2):83-84
An experimental study was carried out on steady-state boiling of sodium flowing in the annular channel formed around an electrically heated simulation of a fuel pin. In the present experiment, the inlet temperature and flow rate were held constant, and the heat flux was gradually increased up to the inception of boiling. Thereafter, the heat flux was further increased step by step until the surface temperature of the heater pin marked a sharp rise, indicating the occurrence of dry-out. Records were obtained of the changes brought by the increasing heat flux to boiling phenomena, with particular reference to the behavior of the two-phase flow pattern and to the characteristics of boiling noise, as well as of the frequency of bubble formation. It was made clear that there exists a region in which steady-state boiling will be established, and under these conditions the two-phase flow pattern changes sequentially from bubbly flow to slug flow and then to annular flow. This behavior of sodium boiling in a narrow channel is quite similar to the case of water. With rising heat flux, the level of noise intensity associated with boiling first increased sharply to attain a maximum point, then decreased somewhat and remained constant thereafter until dry-out. The frequency of bubble formation depended on the size of the bubble. The product of bubble frequency and equivalent diameter was found to be constant. 相似文献