浮顶油罐加热过程的数值模拟

为掌握浮顶油罐内的温度分布,提高加热效率,进行了浮顶油罐内原油加热过程的传热研究。以某2×10~4m~3的单盘浮顶罐为例,基于对浮顶罐加热过程的分析,结合传热学理论,建立了单盘浮顶油罐二维加热模型,应用FLUENT软件对原油加热过程与流动进行了仿真模拟,得到了原油不同加热时间后的温度分布以及原油流场分布,结果表明:原油加热过程中由于自然对流,在浮顶罐内产生漩涡,在罐壁底部流速较低;浮顶罐中心区域内原油温度分布均匀,加热管、罐壁和浮顶下部温度较高。     

从传热学角度分析影响储罐计量准确度的因素

温度是影响油量计量准确度的重要参数。国内长期以来对如何确定罐壁平均温度和罐内油品温度代表性的问题,始终没有一个科学的、指导实践应用的测量和计算方法。文章从工程热力学和传热学的角度,通过研究油品储运过程中罐壁、罐内油品和大气环境间的热能传递规律,探索影响储罐静态计量准确度的各种因素,通过建立数学模型,推导分析传热过程温度场的变化和各种状态环境下罐壁平均温度、油品平均温度以及计量处理方法的合理性和取值规律。     

用最小二乘法回归罐壁温度计算公式

一、概述在大容量计量中,对立式非保温金属油罐进行计量的最后结果应是标准温度20℃时的值。因此,在实际计量中应将油罐在某一温度t℃下的值换算到20℃时的值。但油罐的罐壁温度由于设备本身等限制,很难直接测得。罐壁温度主要是由罐内油品温度和罐外大气温度所决定,故通常是通过这两个温度推算得到罐壁温度。到目前为止,国内外尚未能得出罐壁温度     

黄磷罐的失效分析

同一工艺制造的一批黄磷储运罐,在灌装液态黄磷时,其中一个罐壁穿孔泄漏造成火灾,不久,另一黄磷罐也发生泄漏。为确定失效原因,对穿孔的罐壁进行了化学分析、显微镜观察和扫描电镜分析。结果表明,黄磷罐的泄漏是点蚀和缝隙腐蚀的结果,而腐蚀发生在油漆层破裂或机械划伤使金属暴露的局部区域。含磷酸的密封水（pH在1．61～1．83）具有腐蚀性,加速了腐蚀进程。对长期潮湿搁置的黄磷罐,建议在空罐内注满干燥的氮气或处理过的水以防腐蚀。     

船舶围壁空气层对舱室热环境的影响

采用频域回归法（FDRM）计算4种船舶围壁的动态传热特性,并分析空气层对船舶围壁动态传热及舱室热环境的影响。计算结果表明：空气层对船舶围壁的传热有明显的阻隔作用,且空气层越厚阻隔作用越明显;船舶围壁空气层与保温层的排列次序对围壁传热有一定的影响,空气层在外、保温层在内的排列方式隔热效果更好,内壁温度波动小。     

泄放阀着火时LNG储罐外容器热-结构耦合分析

针对LNG储罐在泄放阀着火的工况,对受到外界高温火焰辐射的LNG外容器的传热和结构进行了耦合分析研究.建立了16万方LNG大型储罐的实体有限元模型,根据规范和相关文献中的推荐方法,获得了泄放阀火焰高温辐射时罐顶外表面的等效辐射温度,根据正常工作时的稳态传热工况进行储罐外容器内表面等效对流传热系数的计算,得到了正常工作时...     

企业动态

“标准金属量器温度修正的实验研究”课题通过鉴定由天津市计量技术研究所承担的研究课题“标准金属量器温度修正的实验研究”今年4月通过了国家质量技术监督局组织的专家组鉴定。该课题中心内容是通过实验确定,当金属量器注入工作介质后,罐壁温度改变引起的容积改变是否存在滞后性,即罐壁温度改变后罐容积量是否立即改变。该课题研究成果达到国内先进水平。（刘焕桥）DDY90系列预付费电能表通过鉴定由北京富根智能电表有限公司生产的DDYto系列预付费电能表,7月对日通过了北京市科委和经委联合组织的技术成果暨产品鉴定。鉴定委员会…     

液氨储罐液体泄漏建模及分析

目的 为了分析液氨储罐纯液体泄漏后的事故影响,探究液氨纯液体泄漏量的计算.方法 针对液氨储罐(卧罐、球罐及立式罐)液体泄漏罐压变化及不同类型储罐结构特征导致液面面积变化的特点,利用范德瓦尔斯方程和流体力学方法,建立液氨储罐液体泄漏模型.利用模型对3种液氨储罐液体泄漏进行数值模拟,对比PHAST计算与模型模拟结果.结论 结果发现液面高度hv,s,h的下降呈现先减缓后增大的趋势,泄漏质量流率Qm-v,s,h的下降幅度及泄漏质量mv,s,h呈现先增加后减缓的趋势.泄漏初始时刻,Qm-v,s,h值最大,分别为0.555,0.553,0.552 kg/s;泄漏停止时,mv,s,h值最大,分别为11.245846,11.084621,7.730932 t.模型计算结果与PHAST模拟结果规律相似,Qm-v,s,h(max)的偏差较小,介于16.577％～16.667％;mv,s,h偏差差别较大,立式罐、球罐及卧罐泄漏液体质量偏差分别为4.565％,5.764％和17.630％.结论 根据各参数的变化规律可得,模型适于计算液氨储罐液体泄漏及风险分析.     

泄露工况下大型LNG预应力混凝土储罐低温分析

借助于ANSYS有限元软件,对大型LNG预应力混凝土储罐由泄露引起的温度场和内力分布进行了深入研究计算,分析了超低温对预应力混凝土储罐结构的影响.结果表明:超低温作用下LNG储罐温度分布由内而外呈线性分布,罐壁的温度分布比较均匀;为减少罐壁中由低温引起的拉应力,同时避免裂缝的出现应在混凝土外罐中合理配置预应力钢筋和热保护角等保冷结构.     

Experimental investigation on heat transfer characteristics of smooth tubes at low mass flux under subcritical and nearcritical pressure

在低质量流速条件下,对垂直上升光管内汽水两相流动沸腾传热特性进行了系统的实验研究.实验段采用了Φ22mm×2.5mm的1Cr18Ni9Ti不锈钢管.实验条件为压力p =10～21MPa,管内质量流速G=448 ～ 1233kg/(m2·s),内壁热流密度q =130～541kW/m2.实验得到了不同工况下垂直上升光管的壁温分布特性.分析了压力、热负荷和质量流速变化对光管传热特性的影响,探讨了传热恶化的发生机理,并给出了能用于工程实际的传热实验关联式.结果表明:在亚临界及近临界压力区,垂直上升光管通常会发生两类传热恶化:膜态沸腾和干涸.压力与热负荷的增大以及质量流速的减小,均会导致传热恶化提前发生和传热恶化后的壁温飞升值增大.与亚临界区相比,光管在近临界区的传热特性变差,发生传热恶化的临界干度下降,甚至在过冷区就发生壁温飞升.     

大型LNG储罐分层破坏及翻滚过程的数值研究

建立了大型LNG储罐分层及翻滚模型,充分考虑了LNG多组分、变物性的特点,分别研究了分层破坏的机理及分层温差、分层高度、漏热量和漏热位置对翻滚剧烈程度的影响。结果表明:当底部漏热为10 W/m~2,上下层温差大于0.2 K时会发生翻滚,且温差越大,翻滚发生越容易,翻滚程度越剧烈。当底部漏热10 W/m~2,上下层高度越接近时,翻滚程度越剧烈。无论是底部漏热还是侧壁漏热,漏热量越大时,翻滚程度越剧烈。漏热量相同时,侧壁漏热发生翻滚的时间要早于底部漏热,但剧烈程度要小于底部漏热。     

大型LNG储罐罐底保冷层结构优化研究

针对大型LNG储罐罐底漏热量大及基础保冷性能差等问题,对储罐底部保冷结构进行了优化,并对不同储罐底部基础的温度场分布和漏热量进行了数值模拟和现场对比分析。结果表明:储罐冷损失与泡沫玻璃砖厚度呈双曲线函数关系,在内外壁温差为185 K时泡沫玻璃砖保冷层厚度设置为600 mm保冷效果显著,再增加厚度时保冷损失减小缓慢;储罐基础采用夯土基础时保冷性能优于柱桩基础,而夯土基础需在罐底设置加热系统,因此工程上大型LNG储罐需根据实际情况进行选择。     

Simulation Research of Vaporization and Pressure Variation in a Cryogenic Propellant Tank at the Launch Site

In order to improve depiction of pressure variation and investigate the interrelation among the physical processes in propellant tanks, a 2D axial symmetry Volume-of-Fluid (VOF) CFD model is established to simulate a large-sized liquid propellant tank when the rocket is preparing for launch with propellant loaded at the launch site. The numerical model is considered with propellant free convection, heat transfer between the tank and the external environment, thermal exchange between propellant and inner tank wall surfaces, gas compressibility, and phase change modeled under the assumption of thermodynamic equilibrium. Vaporization rate of the vented LH2 tank and prediction of pressure change in the tank pressurized with GHe are obtained through simulation. We analysis the distributions of phase, temperature, and velocity vectors to reveal interactions among the propellant’s own convection motion, heat transfer and phase change. The results show that the vaporization rate is mainly affected by heat leaks though the tank wall when the tank is vented, but it does not completely accord with the trend of the leakage because of convection motion and temperature nonuniformity of the liquid propellant in the tank. We also find that the main factors on pressure variation in the pressurized tank are the heat transfer on the tank wall surface bonding the ullage and propellant vaporization which has comparatively less influence.     

高真空多层绝热低温容器真空丧失后的传热试验

利用一个工业化的高真空多层绝热低温量热器,以液氮为介质研究了真空突然丧失对高真空多层绝热低温容器漏热量的影响.主要研究了低温量热器绝热层的变化及破空气体(空气和干燥氮气)的不同对真空丧失后低温容器漏热量的影响,指出绝热层数和破空气体种类都是影响真空丧失后低温容器漏热量的重要因素.     

液氧贮箱增压过程中气枕空间温度场的数值模拟

液氧贮箱增压气体输送过程中,气枕空间的温度场会发生较大的变化,并且会引起相界面附近低温液体的温升.基于双膜阻理论建立热质交换模型,通过模拟贮箱内非稳态热流过程,分析气枕空间在增压气体输送过程中温度场的变化及其对于贮箱内低温液氧的影响.     

Experimental investigation on pressurization performance of cryogenic tank during high-temperature helium pressurization process

Sufficient knowledge of thermal performance and pressurization behaviors in cryogenic tanks during rocket launching period is of importance to the design and optimization of a pressurization system. In this paper, ground experiments with liquid oxygen (LO₂) as the cryogenic propellant, high-temperature helium exceeding 600 K as the pressurant gas, and radial diffuser and anti-cone diffuser respectively at the tank inlet were performed. The pressurant gas requirements, axial and radial temperature distributions, and energy distributions inside the propellant tank were obtained and analyzed to evaluate the comprehensive performance of the pressurization system. It was found that the pressurization system with high-temperature helium as the pressurant gas could work well that the tank pressure was controlled within a specified range and a stable discharging liquid rate was achieved. For the radial diffuser case, the injected gas had a direct impact on the tank inner wall. The severe gas-wall heat transfer resulted in about 59% of the total input energy absorbed by the tank wall. For the pressurization case with anti-cone diffuser, the direct impact of high-temperature gas flowing toward the liquid surface resulted in a greater deal of energy transferred to the liquid propellant, and the percentage even reached up to 38%. Moreover, both of the two cases showed that the proportion of energy left in ullage to the total input energy was quite small, and the percentage was only about 22–24%. This may indicate that a more efficient diffuser should be developed to improve the pressurization effect. Generally, the present experimental results are beneficial to the design and optimization of the pressurization system with high-temperature gas supplying the pressurization effect.     

低温推进剂贮箱增压过程的传热传质数学模拟

针对火箭发动机地面试验中低温液氧贮箱的预增压和增压过程建立了气相空间的传热、传质数学模型.运用实际气体的状态方程、连续性方程、能量守恒方程以及推进剂与气相空间的传热、传质方程等组成了关于气相空间参数的微分方程组,并运用四阶Runge-Kutta算法对其进行求解.获得了气相空间的压力、温度、增压气体流量、液氧挥发速率以及贮箱壁温等参数的变化规律.结果表明,在发动机启动前的预增压过程中,气相空间的温度和压力急剧增加,液氧的挥发速率也增加很快;发动机启动后的保持增压阶段,由于气相空间的体积不断发生变化,气相空间参数的变化趋于平缓,液氧表面向气相空间的传质速率也趋于稳定.     

40英尺液化天然气铁路及其联运罐式集装箱静态蒸发率计算及测试研究

针对铁路及其多式联运液化天然气罐式集装箱,对其静态蒸发率进行了理论计算,在理论计算中引入了温度修正系数kt来考虑装载LNG介质时对液氮温区下绝热层比热流的影响,同时引入了结构修正系数ks来考虑结构和深冷下罐体收缩对支撑部位热传导的影响,采用液化天然气作为介质开展了静态蒸发率试验测试,综合测试结果对理论计算模型进行了验证,在此基础上开展了相关关键参数对LNG罐式集装箱静态蒸发率的影响分析研究。     

Three-dimensional analysis for liquid hydrogen in a cryogenic storage tank with heat pipe–pump system

This paper presents a study on fluid flow and heat transfer of liquid hydrogen in a zero boil-off cryogenic storage tank in a microgravity environment. The storage tank is equipped with an active cooling system consisting of a heat pipe and a pump–nozzle unit. The pump collects cryogen at its inlet and discharges it through its nozzle onto the evaporator section of the heat pipe in order to prevent the cryogen from boiling off due to the heat leaking through the tank wall from the surroundings. A three-dimensional (3-D) finite element model is employed in a set of numerical simulations to solve for velocity and temperature fields of liquid hydrogen in steady state. Complex structures of 3-D velocity and temperature distributions determined from the model are presented. Simulations with an axisymmetric model were also performed for comparison. Parametric study results from both models predict that as the speed of the cryogenic fluid discharged from the nozzle increases, the mean or bulk cryogenic fluid speed increases linearly and the maximum temperature within the cryogenic fluid decreases.