基于相变传热理论的海洋复合管道保温层材料热物性预测及温度调控机理研究

Oil/gas multiphase-flow transportation pipeline is prone to generate wax or hydrates inside the pipeline in the deep-water environment with low temperature. In addition to adopting the insulation layer to preserve the heat inside so as to prevent precipitates from blocking the pipeline, techniques such as electric heating or thermal fluid are additionally employed to maintain the heat storage of the deep-water pipeline, which however, not only has higher requirement for the processing technology and offshore installation precision but also causes a significant increase in pipeline operation cost. The applicant believes that without the adoption of electric heating or thermal fluid technology, the employment of phase change thermal insulation materials to achieve heat charge and discharge can still meet the insulation requirements. To attain this purpose, the key is to establish the correlation mechanism between the thermal properties of phase change composites and the temperature regulation process of marine pipelines. Based on what is mentioned above, this project uses phase change microcapsule composite sandwich pipelines as the object of study, carries out the theoretical research on the heat transfer behaviors of phase change composite sandwich pipelines during the shutdown/restart process and the prediction of effective thermophysical parameters of phase change microcapsule composites, and the experimental research on the preparation and characterization of phase change microcapsule composites, as well as thermal insulation performance tests of phase change sandwich pipelines, which help to form a correlation mechanism between the heat transfer process of sandwich pipelines fabricated of deep-water phase change materials and the thermal properties of the phase change materials, thus providing theoretical guidance for optimizing the preparation technology of microcapsule composites and the development of new marine thermally insulated pipelines.

海洋油气混输管道在深海低温环境下容易在其内部产生蜡结晶或水合物。为防止析出物在管内沉积堵塞，目前行业上除采用保温层对管道保温，还需额外应用电加热或热流体等技术来保持深海管道的蓄热量，但这不仅对加工工艺及海上安装精度要求较高，而且还会大幅增加管道运营成本。申请者认为，不采用电加热或热流体技术，而利用相变保温材料以实现蓄放热，仍然可以满足深海管道的保温要求。要实现这一目的，关键在于建立相变复合材料热物性与海洋管道温度调控过程的关联机制。基于此，本项目以相变微胶囊复合材料夹层管作为研究对象，通过对相变复合材料夹层管停输/重启过程传热行为、相变微胶囊复合材料有效热物性参数预测的理论研究，及相变微胶囊复合材料制备表征、相变夹层管保温性能测试的试验研究，探索深海相变材料夹层管传热过程与相变材料热物性的关联机制，从而为优化相变微胶囊复合材料制备工艺、开发新型海洋保温管道提供理论指导。

本课题设计了满足管道流动保障温度控制要求的相变夹层管道，对长输相变夹层管道传热机理进行了研究，分析了相变温度、导热系数、管道尺寸等因素对管道保温性能的影响，并且提出了电加热海底设计方案，研究了长输管道直接电加热的传热特性。.建立了含有相变夹层的多层长输管道传热模型，分析了长输管道启动阶段及停井阶段内部流体的瞬态温度变化，对相变层厚度比、相变温度、相变层导热系数比及相变滞后现象等进行了研究，得出存在能够实现最长保温时间的最佳相变层厚度比，保温时间随相变温度降低而降低，当相变层导热系数比在一定范围内时，相变层的加入能够显著延长保温时间的重要结论。.建立了复合相变材料传热模型，对复合相变材料内部的微观传热机制进行了研究，推导了复合相变材料的宏观材料属性。并将复合材料宏观热物性运用于相变管道中，分析了含有复合相变材料夹层的长输管道瞬态温度响应、焓值变化、及界面移动情况，研究了相变微胶囊含量、相变层厚度比、不同基质材料及不同相变胶囊材料等对管道保温性能的影响。.提出了针对相变夹层管道复杂传热过程的集总参数模型，设计了相变夹层管道的保温结构，并得到不同初始条件下的相变层厚度比，利用集总参数法对管道保温性能进行分析，研究了相对于传统保温管道相变夹层管道的保温性能。 .基于提出的电加热海底设计方案，建立了直接电加热管道瞬态传热过程的改进集总参数模型，开展了加热功率、流体流速、加热时间等对管道温度分布规律的敏感性分析。对长输管道进行分区间加热分析，研究了初始温度、流体流速、管道长度对加热区间大小和节能效率的影响。.以上成果的取得有利于解决应用相变夹层管道实现流动保障的工程实际问题，为深水海底管道设计及解决流动保障问题提供必要的理论支持，深化了对长输管道保温性能影响机制的认识，对水下长输油气管道保温设计具有重要的参考价值。