【作者】 黄臻成；

【导师】 何振辉；

【作者基本信息】 中山大学 ， 凝聚态物理， 2008， 博士

【摘要】 机械泵驱动的两相回路(Mechanically Pumped Two-phase Loop system, MPTL)是一种具有良好均温性和可控性、适合于分布式热源以及长程传热的控温系统,在控温要求不断提高的航天领域里,它因具有良好的应用前景而重新被人们所重视。在空间热控系统的设计过程中,由于涉及到复杂的太空热流环境,以及真空,微重力等因素,仅仅依靠地面试验无法模拟真实太空环境;而且由于成本、实验技术以及运行周期等因素的制约,地面实验能提供的信息量有限,对某些边界条件极端的、有损害性的工况,实验更是不切实际。因此,需要利用数值模拟的方法为设计提供参考依据。本文利用AMS-2 TTCS作为具体的对象,针对现今研究得比较少、但应用前景突出的机械泵驱动两相系统,利用SINDA/FLUINT平台分别建立了应用于空间模拟的空间动力学模型(dynamic model for space, DMS),和用于实验修正的地面动力学模型(dynamic model for ground test, DMG)。在地面实验平台的测试结果的基础上,对模型的换热器、冷凝器换热和漏热等重要参数进行了拟合和修正,并利用修正后的DMG模拟与实验结果进行验证对比,发现结果符合的较好。由于DMS和DMG的建模数学基础、基本假设以及模型处理方法基本相同,因此证明利用DMS和DMG的模拟结果能正确地反映MPTL的动力学特性,可用于分析和优化设计这类系统。此外,还研究了比较重要但带有不确定性的参数,进而评估模型的可靠性。在此基础之上,本文对系统的控温特性进行深入的分析,利用DMS的模拟结果验证了系统在给定的外热流环境下,收集分散在192个热源、总计144W热量时表现出良好的控温特性,可以达到轨道温度变化小于3℃,9m蒸发器沿程温差小于1℃的控温要求。通过数值模拟,揭示了MPTL蒸发器、换热器、储液器和冷凝器等各个部件对目标温度控制所起的作用以及响应特点,并专门研究了并联冷凝器的因流量自分配而提高散热效果的自调节能力,分析了进出口管长度、边界差异等对其流量调节能力的影响。更进一步地,针对系统冷凝器在极冷工况下会发生的结冰情况,利用模型对特有的冷凝器设计在流向选择和入口管连接进行了优化,使之在具有最佳散热效果的同时,维持不结冰所需热补偿功率最少。然后,使用DMG模拟了蒸发器不平衡加热以及总热量跃变,更进一步验证了蒸发器的稳定性,并且得出储液器的控温受到回路反馈的影响,分析了储液器的控制与回路控制的关系,提出了有效热容的概念。通过储液器开环小热量跃变实验的结果,整理了有效热容与蒸发器加热量的关系,为深入分析储液器有效热容做准备。最后,本文总结了MPTL系统的控温特性,指出这类系统的体积和功耗小,可以胜任长距离散热任务,并且提供高精度控温和良好的温度稳定性。更多还原

【Abstract】 The mechanically pumped two-phase loop system(MPTL) is attracting more interest in space application resently, for its capability of heat collecting, and long-distance heat transferring for distribut heat sources with stable and uniform thermal control. To design the space thermal control system, it is difficult to achieve the real space environment in the ground test, such as complex space condition of the heat flux, vacuum and micro-gravity. Also, the tests on ground are strictly limited by the cost, the technique and the consuming of time. Moreover, some extreme tests may take risks to damage to the system, like freezing or exceeding the system’s highest design temperature, and thus must be forbidden. So, it is necessary to employ numerical simulation to design the thermal control system.The paper describes the thermal analysis of the CO2 MPTL for the Tracker Thermal Control System (TTCS) of the Alpha Magneto- spectrometer-II (AMS-II). By employing the program SINDA/FLUINT, a dynamic model for space (DMS) and a dynamic model for ground test (DMG) are built for analysis the TTCS. The DMS simulates the TTCS operating in the space environment, while the DMG is used for calibration according to the ground test results. Since both of the two models are the same in function, the calibrated DMG can be used to evaluate the reliability of the DMS. With this proposal, the heat exchanger and condenser of the DMG are calibrated, with the heat leak of the condenser return line considered. Finally, the simulation result of modified DMG meets the test result. Moreover, the uncertainty of the key parameters is studied to figure out the reliability of the DMS model.Based on the work above, a study on the MPTL thermal control chararisitic is carried out with the DMS and DMG. The result shows that the TTCS MPTL performs very well to dissipate 144W collected from 192 sources to the space with a long distant (30m) transfer. During the period in orbit, the TTCS provides a stable (<3℃/orbit) and uniform (<1℃/9m) temperature boundary for the tracker hybrids.The DMS result also shows that the condenser will freeze in some extreme cold cases without extra heating power. Depended on the DMS, an optimized anti-freezing of the condenser is design. By choosing the flow direction of CO2, and the contacting position of the condenser inlet, the numerical result shows positive solution for this kind of condenser, for either reducing the anti-freezing power in the cold case or guaranteeing enough subcooling of the pump inlet in the hot case.With a boundary-simplified specific model, the self-adjusted ability of the mass flow in the two parallel condensers is studied. The result shows that the heat dissipation will be greatly improved even up to 40% in cold cases with 4g/s. It is also figured out that the improvement of this ability is related to the flow resistance in the feed and return lines of the condenser, the mass flow rate and the property of the fluid. The simulation result gives a good example for improving the design of this kind of parallel condensers.In order to discuss the relations between the loop and accumulator control, the simulation of imbalance heat load and heat load varying in evaporator are presented with the DMG. The result not only shows the evaporator temperature is still under control precisely, but also tells how the accumulator controls the loop in details. The way of the accumulator controlling the loop is also able to compare with the test result. At last, a concept of effective heat capacity, which related to the thermal control, is presented for the study of this two-phase accumulator. In a pilot study, it is found that the effective heat capacity is related to the loop state.Finally, I summarize the thermal chararisitic of the MPTL from TTCS. It is proved that this cooling system is small in size, and strong for its cooling ability and temperature control precision, capable for long-distance heat transfer for even complex boundary condition.更多还原