海底管道总传热系数的研究与确定

以聚氨脂泡沫塑料为保温材料的双重钢管保温管道为例,结合实验方法,论述套管空气夹层的当量导热系数、保温材料的整管导热系数及材料老化问题,并给出了海底管道的总传热系数计算公式.     

大口径原油输送管道的总传热系数

《油气集输设计规范》附录E"埋地硬质聚氨酯泡沫塑料保温集输油管道总传热系数K选用表"中,给出了保温厚度30 mm和40 mm、公称直径50～250 mm管道总传热系数,但无250 mm以上公称直径管道的总传热系数取值。通过对塔河油田塔—库原油外输线和塔—轮原油外输线的传热系数计算分析得出,对于DN300 mm、30 mm厚硬质聚氨酯泡沫塑料保温管道,在干燥地区,K值可取0.91 W/(m2·℃);对于DN400 mm、30 mm厚硬质聚氨酯泡沫塑料保温管道,在干燥地区和潮湿地区,K值可分别取0.70和0.89 W/(m·2℃)。     

海底油气管线总传热系数的选用

输油输气管道的总传热系数K是管线设计一个十分重要的参数.目前陆地管线设计时K值选用较成熟,但国内对于双层管的海底油气管线总传热系数K的选用没有一个统一规范,只能依靠经验值确定,或由运行的输油输气管线倒推K值.以渤海湾胜利浅海埕岛油田为例,设计海底油气管线时,参照规范<油气集输设计规范(GB50350-2005)>"埋地泡沫塑料保温集输油管线K值选用参照表",DN250(包括DN250)以下管线取中等湿度土壤下K值;DN250以上管线K值取1.0 W/(m·℃).通过运行的数据来验证国内计算公式模型及设计值的可行性,运行状况表明,K值受海底管线施工情况、沿线走向、掩埋情况、外部套管破损情况、海水季节性变化等因素影响.     

正态分布法在已建海底输油管道总传热系数校核中的应用

本文结合某海底输油管道的实际运行数据,反算了该条管道的总传热系数,利用统计学正态分布的方法统计了各个总传热系数的概率密度分布情况,得出管道总传热系数的理想值。应用效果表明,正态分布法对已建海底管道的总传热系数判别是一种实用的方法,具有快速、直观的特点。     

浅埋管道总传热系数的计算

作为计算管道沿程温降的关键参数,总传热系数在热油管道的设计与运行中得到广泛的应用,其值的准确计算对管道的安全、经济运行至关重要.管道总传热系数的计算可采用解析法和数值法.对浅埋管道,解析法比数值法偏保守;当管顶覆土厚度不足0.5 m时,管道埋深越浅,两者的偏差越大;在管顶覆土厚度达到或超过0.5 m后,两者的相对偏差能控制在5％以内.     

计算含蜡原油热输管道总传热系数的新方法

总传热系数是含蜡原油管道设计和运行管理的重要参数之一,其计算应考虑析蜡潜热和沿线参数随温度的变化.本文给出了含蜡原油热输管道总传热系数计算的新方法.模拟计算表明,不考虑析蜡潜热时计算出的总传热系数偏小;进出站温度的准确性对总传热系数计算影响很大,测试时应采用高精度温度传感器测量;自然地温对总传热系数影响较小,建议采用预埋探头的方法进行测试.     

管道总传热系数和当量管径分析

根据管道全年的运行参数计算出大庆油田三条原油管道的总传热系数和当量管径 ,分析了各种因素对总传热系数以及管道结蜡对管道运行的影响 ,指出管道运行工况的稳定程度、站间温降的大小、进出站温度和压力以及地温的测量精度是影响总传热系数和当量管径计算结果的主要因素。对于低输量运行的管线 ,管道结蜡有利于管道的经济和安全运行。     

长输管道总传热系数分析及评价

1．长输管道总传热系数的定义 管道总传热系数即K值指油流与周围介质温差为1℃时，单位时间内通过管道单位传热表面所传递的热量，表示油流对周围介质散热的强弱。对于埋地热油管道，管道传热主要由油流至管壁放热，管壁保温层的热传导和保温层到土壤的散热三部分组成，由热平衡方程关系式化简近似得：     

埋地热油管道总传热系数计算公式的讨论

在简单评述埋地热油管道传热系数公式的基础上,通过理论分析,获得了新的计算公式,并与现有公式进行了对比分析.     

蒸汽管线外表面传热系数计算模型修正

表面传热系数作为计算蒸汽管线热损失的重要参数,其现有经验关联式未考虑因长期使用导致保温层偏心沉降情况的影响。建立了蒸汽管线结构变异模型,采用CFD数值模拟方法,分析了偏心沉降程度对蒸汽管线表面传热系数的影响,修正了管线表面传热经验关联式。结果表明,偏心沉降程度增加,传热系数降低,其下降率呈现先增后减趋势,于沉降程度8%时最低,给出了不同偏心沉降情况下的传热系数关联式,其优度为1。     

考虑总传热系数沿程变化时原油管道计算模型

为了提高计算精度，在管道计算模型中考虑了总传热系数的沿程变化，提出用插值法将土壤导热系数和管线理深表示成距离的函数，然后在每一个分段上分别计算总传热系数、热容、粘度、水力坡降等参数。根据有流型流态改变的原油管道流动特征，建立了计算模型并用数值方法求解。     

关于直埋保温管道传热计算方法的探讨

对于直埋地下的管道,由于环境热阻比较复杂,其传热计算方法尚不统一。文章通过对国内外的几种传热计算方法进行分析对比,并结合多年管道保温工作的实践经验,就直埋保温管道环境热阻率的计算、保温厚度的计算、热影响范围的计算提出建议,与同行探讨。     

Heat Transfer Analysis for Gas-to-Liquids Transportation Through Trans Alaska Pipeline

Gas-to-liquids (GTL) technology involves the conversion of natural gas to liquid hydrocarbons. In this article, theoretical studies have been presented to determine the feasibility of transporting GTL products through the Trans-Alaska Pipeline System (TAPS). To successfully transport GTL through TAPS, heat loss along the route must be carefully determined. This study presents heat transfer and fluid dynamic calculations to evaluate this feasibility. Because of heat loss, the fluid temperature decreases in the direction of flow and this affects the fluid properties, which in turn influence convection coefficient and pumping power requirements. The temperature and heat loss distribution along the pipeline at different locations have been calculated. Fairly good agreement with measured oil temperatures is observed. The powers required to pump crude oil and GTL individually, against various losses have been calculated. Two GTL transportation modes have been considered; one as a pure stream of GTL and the second as a commingled mixture with crude oil. These results show that the pumping power and heat loss for GTL are less than that of the crude oil for the same volumetric flow rate. Therefore, GTL can be transported through TAPS using existing equipment at pump stations.     

Heat Transfer Analysis for Gas-to-Liquids Transportation Through Trans Alaska Pipeline

Abstract

Gas-to-liquids (GTL) technology involves the conversion of natural gas to liquid hydrocarbons. In this article, theoretical studies have been presented to determine the feasibility of transporting GTL products through the Trans-Alaska Pipeline System (TAPS). To successfully transport GTL through TAPS, heat loss along the route must be carefully determined. This study presents heat transfer and fluid dynamic calculations to evaluate this feasibility. Because of heat loss, the fluid temperature decreases in the direction of flow and this affects the fluid properties, which in turn influence convection coefficient and pumping power requirements. The temperature and heat loss distribution along the pipeline at different locations have been calculated. Fairly good agreement with measured oil temperatures is observed. The powers required to pump crude oil and GTL individually, against various losses have been calculated. Two GTL transportation modes have been considered; one as a pure stream of GTL and the second as a commingled mixture with crude oil. These results show that the pumping power and heat loss for GTL are less than that of the crude oil for the same volumetric flow rate. Therefore, GTL can be transported through TAPS using existing equipment at pump stations.     

板翅式热交换器平直翅片流动与传热性能试验研究

通过空气-水传热试验,对平直翅片的流动传热性能进行了研究。试验结果表明,空气流速2.2~5.6m/s时,翅片间空气侧的对流传热系数为50~141W/(m2·℃),流动摩擦压降为40~90Pa。实现翅片高效换热的空气流速是2.2~3.7m/s,对应的翅片总效率在0.85~0.92。     

强化传热在换热器中的应用

介绍强化传热目的、种类及主要方法，分析了各种方法的特点及适用范围和石化生产装置上应用的可行性及发展动态。     

纵横交错管传热及流阻性能研究

以水为工质,对纵横交错管和圆管在不同流速下的传热性能和压降进行模拟,获得了湍流状态下二者管内温度场和速度场的分布。通过对两种管型性能的比较研究,发现随着Re的增大,交错管管内传热系数比光管平均提高29.68%,压降也明显增大。