Cryogenic loop heat pipes are highly efficient heat transfer devices at cryogenic temperature range,which have promising application prospects in satellites,spacecrafts,electronics,and so on.Cooling down process is a ...Cryogenic loop heat pipes are highly efficient heat transfer devices at cryogenic temperature range,which have promising application prospects in satellites,spacecrafts,electronics,and so on.Cooling down process is a most critical process for a CLHP before startup.At present,secondary loop is a major way for a CLHP to fulfil cooling down and most studies are concentrated on heat transfer characteristics during normal operation.However,few investigations have been carried out on the cooling down process.In this paper,the cooling down process of a nitrogen-charged CLHP assisted with a secondary loop was experimentally investigated.A simple qualitative approach to estimate the cooling down time was proposed according to the law of conservation of energy.The two flow paths of the working fluid in the CLHP during the cooling down process were described.Experimental studies on the cooling down process with various secondary heat loads and working fluid inventory were presented in detail.With the increase of secondary heat load,the elapsed time of Stage III decreased significantly due to the larger mass flow rate in Path I.In addition,the effect of the working fluid inventory on the cooling down time was generally small in the range from 2.99 MPa to 3.80 MPa.However,with 2.80 MPa working fluid inventory,it required much longer cooling down time,which was because of the lack of liquid in the CLHP with low working fluid inventory.Moreover,the influence of gravity on the temperature variation of the components during the experiments was analyzed.This work is beneficial for better understanding of the cooling down process and optimizing of CLHPs.展开更多
采用流热耦合方法分别对内部冷却的超跨音直列叶栅和环形叶栅进行数值模拟。其中直列叶栅为径向圆孔内冷的NASA MARK II叶片,通过数值解与实验值的对比,验证流热耦合方法的准确性,并讨论层流、不同湍流及转捩模型在流热耦合模拟中的特...采用流热耦合方法分别对内部冷却的超跨音直列叶栅和环形叶栅进行数值模拟。其中直列叶栅为径向圆孔内冷的NASA MARK II叶片,通过数值解与实验值的对比,验证流热耦合方法的准确性,并讨论层流、不同湍流及转捩模型在流热耦合模拟中的特点。在此基础上选用考虑和不考虑转捩模型的SST湍流模型,以采用径向成形内冷通道的某高压级导叶环形叶栅为研究对象,讨论其复杂流场与换热之间的相互作用。结果表明:为准确预测流热耦合作用下的温度分布,需要选择合理的湍流模型,并考虑转捩的影响,不同热边界同样会影响气动效果如分离再附等;三维超跨音流场中激波、分离以及通道涡、角隅涡等涡系结构与温度场之间存在复杂的相互作用;内部换热对于降低叶片表面温度有着重要作用,通过数值解可指导冷却结构优化设计。展开更多
针对某厂240 mm×280 mm 45钢连铸矩形坯的内部质量缺陷,建立了基于射钉和测温验证的铸坯温度场实时跟踪计算模型,同时,根据目标表面温度对二冷水量进行优化,并应用了动态二冷配水系统。结果表明,动态配水考虑了传热过程的滞后性,...针对某厂240 mm×280 mm 45钢连铸矩形坯的内部质量缺陷,建立了基于射钉和测温验证的铸坯温度场实时跟踪计算模型,同时,根据目标表面温度对二冷水量进行优化,并应用了动态二冷配水系统。结果表明,动态配水考虑了传热过程的滞后性,在拉速波动时能更好地控制铸坯表面温度;铸坯质量得到明显改善,中心疏松、缩孔、中间裂纹和中心裂纹等缺陷都有不同程度的减轻,且基本消除1级以上的缺陷。展开更多
基金supported by the National Natural Science Foundation of China(No.51606207)Youth Innovation Promotion Association,CAS,China(No.2018036)partially supported by Beijing Municipal Natural Science Foundation(No.3202033)。
文摘Cryogenic loop heat pipes are highly efficient heat transfer devices at cryogenic temperature range,which have promising application prospects in satellites,spacecrafts,electronics,and so on.Cooling down process is a most critical process for a CLHP before startup.At present,secondary loop is a major way for a CLHP to fulfil cooling down and most studies are concentrated on heat transfer characteristics during normal operation.However,few investigations have been carried out on the cooling down process.In this paper,the cooling down process of a nitrogen-charged CLHP assisted with a secondary loop was experimentally investigated.A simple qualitative approach to estimate the cooling down time was proposed according to the law of conservation of energy.The two flow paths of the working fluid in the CLHP during the cooling down process were described.Experimental studies on the cooling down process with various secondary heat loads and working fluid inventory were presented in detail.With the increase of secondary heat load,the elapsed time of Stage III decreased significantly due to the larger mass flow rate in Path I.In addition,the effect of the working fluid inventory on the cooling down time was generally small in the range from 2.99 MPa to 3.80 MPa.However,with 2.80 MPa working fluid inventory,it required much longer cooling down time,which was because of the lack of liquid in the CLHP with low working fluid inventory.Moreover,the influence of gravity on the temperature variation of the components during the experiments was analyzed.This work is beneficial for better understanding of the cooling down process and optimizing of CLHPs.
基金National Basic Research Program of China (2007CB707701)National Natural Science Foundation of China(51106124)Research Fund for the Doctoral Program of Higher Education of China (20100201120007)
文摘采用流热耦合方法分别对内部冷却的超跨音直列叶栅和环形叶栅进行数值模拟。其中直列叶栅为径向圆孔内冷的NASA MARK II叶片,通过数值解与实验值的对比,验证流热耦合方法的准确性,并讨论层流、不同湍流及转捩模型在流热耦合模拟中的特点。在此基础上选用考虑和不考虑转捩模型的SST湍流模型,以采用径向成形内冷通道的某高压级导叶环形叶栅为研究对象,讨论其复杂流场与换热之间的相互作用。结果表明:为准确预测流热耦合作用下的温度分布,需要选择合理的湍流模型,并考虑转捩的影响,不同热边界同样会影响气动效果如分离再附等;三维超跨音流场中激波、分离以及通道涡、角隅涡等涡系结构与温度场之间存在复杂的相互作用;内部换热对于降低叶片表面温度有着重要作用,通过数值解可指导冷却结构优化设计。
文摘针对某厂240 mm×280 mm 45钢连铸矩形坯的内部质量缺陷,建立了基于射钉和测温验证的铸坯温度场实时跟踪计算模型,同时,根据目标表面温度对二冷水量进行优化,并应用了动态二冷配水系统。结果表明,动态配水考虑了传热过程的滞后性,在拉速波动时能更好地控制铸坯表面温度;铸坯质量得到明显改善,中心疏松、缩孔、中间裂纹和中心裂纹等缺陷都有不同程度的减轻,且基本消除1级以上的缺陷。
