非均匀热流下太阳能熔盐吸热器传热特性及强化机理研究

This project aims to design high efficiency molten salt receiver with the background of developing heat transfer and heat storage technology in solar thermal power. The heat transfer influence of external surface heat flux distribution is discussed on the characteristics of receiver tube with circumferential and axial nonuniform heat flux, and the relationship of average and local heat transfer coefficient in molten salt receiver tube are explored. The heat transfer effect of unilateral transversely corrugated tube structure parameter is researched, at the same time, the heat efficiency of receiver is calculated, the heat transfer correlation in unilateral transversely corrugated tube is obtained. The heat transfer model of molten salt in unilateral transversely corrugated tube receiver is established, and the enhancement of heat transfer mechanism is revealed. Besides, thermal stress of receiver tube is analyzed in order to forecast the maximum heat flux. By considering the heat transfer performance evaluation criteria, the structure parameter of unilateral transversely corrugated tube receiver is optimized, and this result can provide theoretical basis for high efficiency receiver design.

本项目以发展太阳能热发电高效传热蓄热技术为基础研究的工程背景，提炼出开发高效熔盐吸热器作为研究目标。针对吸热器管壁周向和轴向非均匀受热的特点，探悉光管吸热器管壁热流分布对管内熔盐传热的影响规律，探寻吸热器管内平均传热系数与局部传热系数之间的深层次关系，揭示管壁热流对管内熔盐传热的影响机制。设计并研制单侧横纹管吸热器，探索单侧横纹管结构参数等对管内熔盐传热特性的影响规律，计算并分析单侧横纹管吸热器的吸热效率，提出熔盐在单侧横纹管吸热器内的传热关联式。建立非均匀热流下熔盐在单侧横纹管吸热器内流动与传热的数理模型，揭示单侧横纹管强化传热的机理，深入分析非均匀热流下管壁的热应力分布，预测管壁热流密度极限值的范围。评价非均匀热流下单侧横纹管吸热器的综合传热性能，优化单侧横纹管吸热器的结构参数，为设计高效吸热器提供科学依据。

本项目以发展太阳能热发电高效传热蓄热技术为基础研究的工程背景，提炼出开发高效熔盐吸热器作为研究目标。通过实验研究了轴向和周向非均匀热流下光管吸热器管内熔盐传热特性，得到了含有周向热流比和轴向热流比的吸热器管内传热关联式。建立周向非均匀热流下吸热管模型，分析了吸热管壁厚、熔盐温度、熔盐流速对局部传热性能的影响规律。揭示了管壁周向热流对管内熔盐传热的影响机制，探寻了吸热器管内平均传热系数与局部传热系数之间的深层次关系，提出了周向非均匀热流下吸热管单侧对流传热系数的计算方法。建立了半周加热横纹管内熔盐对流传热的实验台和数值计算模型，得到了横纹管槽宽、槽深对管内熔盐局部和平均传热Nu数的影响规律，分析了凹槽内熔盐流动对管内传热的影响，得到了半周加热横纹管内熔盐传热Nu数的关联式。研究得到单侧横纹管的综合性能评价因子PEC大于横纹管的PEC，设计并研制单侧横纹管吸热器，探索了单侧横纹管结构参数等对管内熔盐传热特性的影响规律，分析非均匀热流下槽深对单侧横纹管强化传热的影响机制，优化了单侧横纹管吸热器的结构参数，为设计高效吸热器提供科学依据。研究了非稳态条件下熔盐吸热管的瞬态传热特性，得到了管外壁热流突变、流速突减、热流和流速同时突减对吸热管传热特性的影响规律，为太阳能吸热器非稳态运行设计及控制提供理论基础。