熔盐横向冲刷过冷沸腾水传热特性实验研究

熔盐-汽水换热器性能直接影响塔式太阳能热电站的发电效率,以太阳盐为工质,实验研究了熔盐横掠冲刷管内过冷沸腾水传热特性,工况参数为：熔盐质量流速504～594 kg/(m²·s),熔盐温度350～560℃;管侧质量流速135～226 kg/(m²·s),入口温度260℃,热流密度65～465 k W/m²。研究影响熔盐换热器传热,特性的关键参数与次要参数,其中熔盐温度及水侧压力对传热特性影响较大。最后,将实验数据与文献中的关联式进行了对比分析。     

CaCO3垢的形成对池核沸腾传热的影响

在一水平圆形加热表面上通过实验考察了饱和池核沸腾和过冷池核沸腾时CaCO3垢的生成对传热的影响。结果表明，在饱和池核沸腾和过冷池核沸腾的初始阶段沸腾传热系数均呈先降低后升高、达到一个最大值后稳定降低的趋势，而且在初始阶段出现了负污垢热阻现象。在相同操作条件下，过冷池核沸腾传热系数明显低于饱和池核沸腾传热系数。在分析污垢的生成和生长影响表面活化中心的基础上，对污垢的形成对沸腾传热的影响进行了机理分析。     

熔盐横向冲刷管内汽-液两相流传热特性实验研究

以太阳盐为工质,实验研究熔盐横向冲刷管内汽-液两相流的传热特性。分析熔盐质量流速、熔盐入口温度、水侧压力、水侧质量流速、水侧干度对熔盐与汽-液两相流的传热特性的影响规律。实验结果发现熔盐入口温度及水侧干度对熔盐蒸汽发生器的性能影响较大。     

矩形通道干涸后膜态沸腾传热试验研究

在流动传热基础试验平台上进行了矩形通道干涸后膜态沸腾的传热试验,研究了各种热工水力参数对膜态沸腾传热的影响特性.结果表明:干涸后膜态沸腾是一个相对稳定的传热过程,其壁面温度不会出现明显的脉动;随着进口含汽率的增加,膜态沸腾热流密度减小,壁面温度升高,传热系数减小;随着质量流速的增大或系统压力的升高,膜态沸腾热流密度增大,壁面温度降低,传热系数增大.     

考虑沸腾和缸内局部传热的缸盖流固耦合传热分析

以某商用车直列6缸柴油机作为研究对象,基于缸内传热模型获得内燃机缸盖和缸套的燃气侧局部传热边界条件;基于均相流沸腾传热模型获得水侧传热边界;实现水侧、燃气侧边界与结构温度场计算的耦合,并判断水腔内沸腾传热的状态。结果表明:缸盖温度计算值与实测值吻合,缸盖最高温度位于缸盖底面两个排气门之间;排气门之间的燃气传热系数和燃气温度均处于较高值,缸内局部传热显著;在缸盖底面中心和排气门附近水腔内的冷却水处于部分发展泡核沸腾状态。     

熔盐与亚临界汽/水在管壳换热器中传热特性实验研究

以太阳盐（Solar Salt）为工质，实验研究熔盐与过热蒸汽/亚临界水在管壳式换热器中的流动传热特性，并开展管侧及壳侧流量、入口温度、压强等参数对熔盐流动传热的敏感性研究。实验结果表明，熔盐入口温度对其传热规律影响较大。根据传热相似原理，获得熔盐与单相汽、水传热的修正关联式，其与实验值的最大偏差分别为±10%,-15%。     

带定位格架的5×5棒束通道内过冷沸腾流动传热数值研究

基于流体体积函数(VOF)两相流模型,通过在控制方程中加入适当的质量源项和能量源项,建立了过冷沸腾模型,利用该模型对5×5定位格架棒束通道内的过冷沸腾现象进行数值模拟,研究了有无过冷沸腾现象2种工况下的传热特性以及入口速度、入口过冷度等因素对燃料组件内传热特性的影响。结果表明:有过冷沸腾现象时流体的传热效果优于无过冷沸腾现象,在有过冷沸腾现象时,总体上通道内传热系数与入口速度呈正相关,与入口过冷度呈负相关;在局部区域,相变传热占据主导因素,过冷沸腾程度越强,流体的传热效果越好。     

竖直矩形窄通道内沸腾换热特性及液滴夹带的实验研究

对通道尺寸为1 400 mm×250 mm×2.75 mm的竖直矩形窄通道内沸腾换热特性及液滴夹带进行了实验研究,分析了不同液位、加热蒸汽流量、补液温度下换热性能以及液滴夹带的变化规律。实验结果表明：随着初始液位高度的提高会出现一个拐点,在到达拐点后,继续提高初始液位以及增加补液量将不会改变最终液位的高度;实验段的传热系数随着液位的升高先增大,并在拐点附近达到最大值,随后减小;在相对液位低时,未出现液滴夹带,而当液位逐渐接近液位拐点时,通道出口逐渐出现液体,而夹带量在液位达到拐点后迅速上升;随着加热蒸汽流量的提高,换热量的增加使沸腾换热更加剧烈,传热系数和带液量显著增大;补液温度越高,传热系数越大,但是补液温度对带液量无明显影响。     

含高浓度CO2的水蒸气在竖直平板上的凝结换热实验研究

对含有高浓度CO2的水蒸气在竖直平板上冷凝传热特性进行了实验研究,得到了混合蒸气流速为0．8 m／s、CO2质量分数为60．0％～94．0％工况下的凝结传热特性曲线。结果表明,CO2的加入会极大恶化蒸汽的凝结传热,随过冷度的增加凝结传热系数逐渐降低,且随着CO2质量分数的增大,凝结传热系数受过冷度的影响越来越小;随着CO2质量分数的增加,凝结传热系数继续降低,但降低幅度逐渐减缓。对比高CO2质量分数下膜状和珠状凝结传热特性发现,珠状凝结并没有明显强化传热优势。     

增压富氧燃烧流化床炉内传热特性

建立了增压富氧燃烧流化床锅炉炉内传热模型.通过模型计算,分析了颗粒粒径、空隙率、床层温度及系统压力等因素对炉内传热特性的影响.结果表明：随着颗粒粒径增大,传热系数减小;随着空隙率增大,传热系数减小;随着温度升高,传热系数增大;随着压力升高,传热系数增大,但增加的幅度明显变小,说明当压力升高到一定程度时,继续升高压力对传热没有太大影响.     

低熔点熔融盐管内强迫对流换热的实验研究

利用课题组自行配制的二元混合熔融盐(KNO3-Ca(NO3)2)开展导热油与低熔点熔融盐的管内强制对流实验研究。通过实验得到导热油与低熔点熔融盐的总换热系数,并通过最小二乘法和Wilson分离法得到了管内低熔点熔融盐侧的对流换热系数及其准则关联式。与不同的经典传热关联式对比,最大偏差为+23%。考虑高温熔融盐的变物性特征,利用黏度项对Dittus-Boelter方程关联式进行修正。经过修正后的Dittus-Boelter方程与实验测试结果最大偏差为-15%,偏差值明显减小。过渡流实验数据和Hausen方程及Gnielinski方程的最大偏差均为10%,实验结果验证了传热关系式仍适用于高温熔融盐的结论。     

Turbulent convective heat transfer with molten salt in a circular pipe

In order to understand the heat transfer characteristics of molten salt and testify the validity of the well-known empirical convective heat transfer correlations, an experimental study on turbulent convective heat transfer with molten salt in a circular tube was conducted in this paper. Molten salt circulations were realized and operated in a specially designed system over 1000 h. The flow rates and temperatures of molten salt and mineral oil at the inlet and outlet in the test section were measured and the average forced convective heat transfer coefficients of molten salt were determined by least-squares method. Finally, heat transfer correlations of turbulent flow with molten salt in a circular tube were obtained. Good agreement was observed between the experimental data of molten salt and the existing well-known correlations. The experimental data of molten salt in the present work are consistent with experimental results reported by different references in a wide range of Prandtl numbers from 0.7 to 59.9.     

含氧类导热油的探索

导热油作为间接加热的热载体于工业生产,已有几十年的历史了。利用载体间接另热的优越性,早在利用水、蒸汽、熔盐和液态金属的初期就已经显现出来了。因此们们一直致力于适合各种温度的热载体的研制、生产、通过对含氧类有机化合物作为导热油的研究发现,含氧类导热与烷基、芳在导热油相比较,在使用上有其独到之处。     

Pretest in forced circulation molten salt heat transfer loop: Studies with thermia‐B

Molten salts have potential application as an efficient heat transfer medium in a primary and secondary heat exchanger in high temperature next‐generation nuclear power plant. Thermal hydraulic studies are vital for reliable and cost‐effective design of the nuclear power plant. Therefore heat transfer study of molten salts will play a vital role in this area. In this work, an experimental system was designed to study thermal hydraulics of the molten salt system up to 700°C. This work describes the pretest results of the experimental facility for extremely corrosive molten fluoride salts with a simulant thermia‐B as the working fluid. In the present work, the details of the system are discussed and thermal‐hydraulic data for heat transfer fluid thermia‐B has been presented. Experiments were carried out at Reynolds number in the range of 4500 to 40 500 and Prandtl number in the range of 34 to 144. Effect of Reynolds number, melting tank temperature, and heat input to test section on forced convective heat transfer was studied under turbulent conditions. Comparison of the experimental data with different empirical correlations has been presented.     

Experimental research of boiling heat transfer of smooth and screwed tube

In this paper, based on the analog theory of heat transfer research, we performed an analog experiment on boiling heat transfer in smooth tube and screwed tubes. These are widely used in the high pressure generator of lithium bromide absorption refrigeration. From the experimental research, we obtained a series of results on the boiling heat transfer of a single smooth tube and three screwed tubes. The working condition is near the zone of bubble boiling and the overheat wall temperature ranges from 2–7 °C, with a fluid medium of pure water and salt water solution. These results agreed well with the known results, and are significant for the practical design and application of a high pressure generator of lithium bromide absorption for refrigeration. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(2): 74–84, 2007; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/htj.20145     

高温熔盐吸热器的传热研究和系统设计

本文对非均匀辐射热流密度太阳能熔盐吸热器传热过程进行了模拟研究,得到了熔盐吸热器内部的温度、传热性能等特征参数。结果表明在轴向和径向上熔盐流体温度和管壁的温度都非常不均匀,同时其综合传热性能要高于按照Sieder-Tate公式的计算值。并对10 MW塔式太阳能热发电的熔盐吸热器进行了设计和分析。     

螺旋扭曲椭圆管换热器壳程数值模拟

以水为介质,采用k-ε模型,用数值模拟方法研究了5种不同结构的螺旋扭曲椭圆管换热器的管外壳程传热与流阻性能,并和采用椭圆管作为换热部件的换热器进行了比较.研究结果表明,螺旋扭曲椭圆管换热器壳程有较好的强化换热特性,螺旋扭曲椭圆管的几何尺寸和流体流动速度对壳程传热与流阻性能有重要影响.通过数值模拟所获得的规律为螺旋扭曲椭...     

Experimental study on the heat transfer characteristics of fluoride salt in the new conceptual passive heat removal system of molten salt reactor

A new conceptual design of a passive residual heat removal system (PRHRS) has been proposed for molten salt reactor. High‐temperature heat pipes are used in this new design to improve the system inherent safety and make the PRHRS more compact. An experimental system using fluoride salt FLiNaK has been constructed to validate and support the future design of PRHRS of molten salt reactors. In this research, tests on the natural convection heat transfer of FLiNaK in the drain tank with an inclined heat pipe inserted at different heights were performed. The temperature distribution of fluoride salt in the tank was analyzed. The height of heat pipe and the bulk temperature of FLiNaK have little influence on the normalized salt temperature distribution. However, with the height of heat pipe increasing, the temperature difference of molten salt decreases and heat transfer coefficient of natural convection increases. In addition, the empirical correlations of natural convection heat transfer between liquid FLiNaK and inclined heat pipe are obtained within the range of Rayleigh numbers from 3.97 × 10⁶ to 1.16 × 10⁷. The comparisons show that a good agreement with less than 5% deviation is obtained between the proposed correlations and the test data.     

用于太阳热发电的铅-铋合金传热特性分析

介绍了液态铅-铋(LBE)合金的热物理及传热特性,提出了将铅-铋共晶合金用于太阳热发电高温传热工质的构想.并建立了流体传热特性计算模型,对液态铅-铋合金与传统太阳热发电传热工质-熔盐的传热特性进行了对比模拟计算.结果表明:在热力循环中,采用液态LBE合金作为传热工质与熔盐相比,不但具有更高的热效率和热经济性,而且还可大大节省投资成本,因此其作为高温传热工质在太阳能热发电领域具有广阔的应用前景.     

Heat transfer enhancement and performance of the molten salt receiver of a solar power tower

This paper investigates the interaction between the heat transfer performance and the thermal efficiency of a molten salt receiver used in the solar power tower plant. A test-bed is built, and a series of experiments of heat transfer enhancement for two types of molten salt receiver tubes, including smooth and spiral tubes, have been carried out under the high temperature and the high heat flux conditions. The experimental results show that the Nusselt numbers of spiral tube with heat transfer enhancement are in the range of 400–1200, which is about 3 times than that of the smooth one on average. The wall temperature of the spiral tube is decreased by about 30 °C comparing with that of the smooth tube under the identical heat transfer conditions. The results of the experiment show that, by using the spiral tube as the heat transfer tube, the heat transfer performance of the molten salt receiver is obviously improved, and the radiation and convection losses are significantly reduced. The results will be helpful for the design of the molten salt receiver.