共查询到18条相似文献,搜索用时 140 毫秒
1.
2.
3.
以去离子水为工质的高温流体 ,由下向上流过电加热内、外管壁间的环形狭缝 ,对同心竖直环形狭缝进行了干涸后换热试验研究。试验结果表明 :环形缝隙中的干涸后换热 ,与普通环形通道中的换热有着明显不同。试验中发现在相同热流密度下内管换热能力大于外管。应用Groeneveld公式 ,拟给出适合试验数据的换热公式。在试验的基础上 ,对内外管中较大的热流密度 ,与内外管热流密度的平均值的比值建立变量 ,并应用多元线性回归方法 ,建立了适合工程实际应用的环形狭缝通道干涸后传热计算经验关联式。 相似文献
4.
对液态金属钠在环形通道内的单相流动换热特性进行了实验研究。结合实验数据,将液态金属钠单相流动分为层流区(Re≤2 000)、过渡区(2 000Re≤4 000)及湍流区(Re4 000),分别拟合得到不同流态下摩擦系数的计算关系式,并拟合得到液态金属钠环形通道内换热特性的相应关系式。结果表明:液态金属钠单相流动特性与常规流体(如水)类似,其层流区摩擦系数略大于水,湍流区与水的很接近。液态金属钠对流换热过程中,导热项占较大份额,同时Nu随Pe的增大而略有增大。 相似文献
5.
骨架发热多孔介质内单相水流动传热实验研究 总被引:1,自引:0,他引:1
针对骨架发热多孔介质内单相水流动阻力和传热特性开展了实验研究,拟合获得骨架发热多孔介质内热态流动阻力和对流换热关系式。实验参数范围是:雷诺数Re取127~394,表面热流密度12~62 kW/m2。实验结果表明:在本文研究的孔隙有效雷诺数范围内,惯性项阻力系数Rf受流动参数影响;基于骨架发热条件下获得的阻力关系式具有较好的扩展性,可以较好地预测骨架不发热条件下多种几何结构的多孔介质通道内单相水、单相蒸汽流动阻力;随着表面热流密度增大,对流换热系数不断降低;在相同热流密度条件下,随着质量流速的增大,对流换热系数也会随之增大。 相似文献
6.
矩形窄缝通道内水稳态和瞬态流动换热特性实验 总被引:1,自引:0,他引:1
以去离子水为工质,在压力0.5~5.0 MPa的范围内,对矩形窄缝通道内水稳态及瞬态流动换热特性进行了实验研究。结果表明:矩形窄缝通道在水平和竖直放置以及稳态和瞬态条件下,水的流动换热特性呈现出基本相同的规律。层流向紊流过渡区域的雷诺数(Re)为900Re1300,比常规通道提前,单相摩擦阻力系数比常规通道大;采用Dittus-Boelter公式的形式拟合得到了新的换热实验关联式,其系数较Dittus-Boelter公式的系数约小11.3%。在稳态条件下,紊流区换热系数随质量流速的增加而增大,增大趋势比较明显;换热系数随热流密度的变化不明显;压力对单相强迫对流换热特性基本没有影响。 相似文献
7.
8.
矩形窄缝通道流固共轭传热数值分析 总被引:1,自引:0,他引:1
优化设计矩形窄缝流道角部非加热区时,需了解该区域固体的温度场及导热机理对换热的影响.本文采用CFD软件CFX对矩形窄缝通道内流固共轭传热进行了数值分析.研究结果表明:角部附近设计1 mm×2 mm非加热区域后,能够有效地避免角部热集中现象,非加热区对流道中间部位温度场的分布影响不大;非加热区域固体设置为导热边界条件时,角部附近加热面上的内壁面热流密度和温度的分布变得不均匀;同体金属材料的热传导使得非加热区域内固体的温度有所升高,有利于提高该区域流体的温度;非加热区域固体设置为绝热边界条件时,等体积热流密度和等壁面热流密度对矩形通道内的换热性能影响不大. 相似文献
9.
10.
11.
12.
WU Ge-Ping QIU Sui-Zheng SU Guang-Hui JIA Dou-Nan LU Dong-Hua 《核技术(英文版)》2006,17(4):252-256
1 Introduction There are basically two classes of critical heat flux (CHF) situations: departure from nucleate boiling (DNB) and dryout (DO) [1]. DO is also sometimes known as burnout or departure from forced convective boiling in vapor-continuous flow. From the point of view of engineering, the CHF caused by the DO mechanism is of particular importance since boiling annular flow is one of the most common flow patterns in gas–liquid two-phase flow and occurs in a wide range of vapor qua… 相似文献
13.
14.
15.
《Journal of Nuclear Science and Technology》2013,50(3):279-281
The importance of heat transfer in a narrow gap has been pointed out in relation to the in-vessel retention of molten core under a severe accident condition of a light water reactor. In this study, heat transfer experiment has been carried out using internally heated annuli with a narrow gap and closed bottom. Effects of gap clearances (1.0, 2.0, 4.0 mm) on the cooling process were examined. The inner wall initially heated up to 800°C was cooled down by water supplied to the upper plenum, the transient rod temperature being measured. From the temperature history, transient boiling curves were obtained, which were compared with predictions by existing heat transfer correlations for nucleate boiling critical heat flux (CHF) and film boiling. In narrow gap channels water penetration to the gap was restricted by counter flowing vapor, which lead to a decrease of heat transfer coefficients. 相似文献
16.
Effects of gap sizes (3.9–44.3 mm) of vertical annuli on nucleate pool boiling heat transfer of water at atmospheric pressure have been obtained experimentally. Through the tests, the conditions of tube bottom confinement (open or closed) have also been investigated and the whole results are compared with those of a single unconfined tube. According to the results, the annular condition gives much increase in heat transfer at moderate heat fluxes. The increase is much enhanced as the gap size decreases. At the same tube wall superheat (about 3.2 K) the heat flux of the least gap size is more than four times greater than that of the unconfined tube. Its effect is observed much greater for the bottom-closed tube condition. However, a deterioration of heat transfer occurs at high heat flux for confined boiling. 相似文献
17.
AYE Myint 《核技术(英文版)》2005,16(1):53-58
Prediction of dryout point is experimentally investigated with deionized water upflowing through narrow annular channel with 1.0 mm and 1.5 mm gap respectively. The annulus with narrow gap is bilaterally heated by AC current power supply. The experimental conditions covered a range of pressure from 0.8 to 3.5 MPa, mass flux of 26.6 to 68.8 kg?m-2?s-1 and wall heat flux of 5 to 50 kW?m-2. The location of dryout is obtained by observing a sudden rise in surface temperature. Kutateladze cor… 相似文献
18.
在窄缝流道内发生沸腾换热现象时,由于沸腾产生的汽泡受窄缝流道的限制,受压变形而消除了汽泡表面张力对传热的影响。因此对此现象进行基础性理论研究具有很重要的意义。本文在常压下用蒸馏水对窄缝间隙为 0.75mm的垂直环形流道,进行了流动沸腾传热实验研究。实验段的有效加热长度为 900mm,其加热方式为内外侧双面加热,实验的流量变化范围在 1.67× 10- 5~ 5.83× 10- 5m3/s。通过实验得到了在不同质量流速和热流密度下双面加热的窄缝流道中内外侧沸腾换热系数随干度变化的分布和特点。研究结果表明,由于在窄缝流道中存在着大量的运动聚合受压变形汽泡,因此使内外侧沸腾换热系数都很高 (可达 105W· m- 2· K- 1以上 )。 相似文献