充液率对钠钾合金热管运行特性的影响研究

Na-K alloy is an excellent working fluid which could be used to fill high-temperature heat pipes. Compared with Na and K, Na- K alloy is liquid at room temperature, so it is difficult to solidify in the heat pipe when starting up and normally running, and can effectively avoid the risk of overheating in the evaporator section. Since it is not clear how the filling rates of Na-K alloy affect the operational characteristics of the heat pipe, so it is not possible to get the best filling rate under different working conditions of Na-K alloy heat pipe, and that’s why the Na-K alloy heat pipe technology developed slowly. This project intends to experimentally research startup times, stability and uniformity of the wall temperature fields, resistances of heat transfer of Na-K alloy heat pipes with different filling ratios, in order to reveal the rules how Na-K alloy filling rates affect startup characteristics, variable characteristics of wall temperature fields and the maximum heat transfer possibility of different heat pipes. The startup time of heat pipes will be determined by the response speed of temperatures of different positions of the heat pipe to the heat source, and the uniformity and stability of the heat pipes’ wall temperature fields are measured by the standard deviations, and the resistances of heat transfer will be computed by the average temperatures of the cold sections and hot sections and average qualities of the heat transfer. After above research works, we will finally reveal the rules how the Na-K alloy filling rate affects the operational characteristics of the heat pipes, and get the theoretical method to predict the operating characteristics of Na-K alloy heat pipes by the filling rates, to provide a scientific basis for the rational filling and application of Na-K alloy heat pipes .

钠钾合金是可用于充装高温热管的优良工质。与钠、钾相比，钠钾合金由于常温下为液态，故在热管启动和正常工作中不易凝固，能够有效避免蒸发段干烧过热的危险。由于尚不清楚钠钾合金充液率对热管运行特性的影响规律，故无法获得不同工作环境下钠钾合金热管的最佳充液率，因此钠钾合金热管技术发展缓慢。本项目拟在给定的高温高强度热源环境下，对不同充液率的钠钾合金热管的启动时间、壁面温度场的稳定性及均匀性、传热阻进行详细的实验研究，旨在揭示钠钾合金充液率对热管启动特性、温度场时空变化特性、最大传热能力的影响规律。拟通过热管的不同位置对热源温度的响应速度确定启动时间，通过壁面温度的标准差衡量热管温度场的均匀性和稳定性，通过平均传热量和冷、热端平均温差计算热管传热阻。经过以上研究，揭示钠钾合金充液率对热管运行特性的影响规律，形成通过充液率预测钠钾合金热管运行特性的理论方法，为钠钾合金热管的合理充装及应用提供科学依据。

本项目研究高温高强度热源下，不同充液率的钠钾合金热管的启动时间、壁面温度场的稳定性及均匀性等传热特性。旨在揭示钠钾合金充液率对热管启动特性、温度场时空变化特性、最大传热能力的影响规律。经过以上研究，揭示钠钾合金充液率对热管运行特性的影响规律，形成通过充液率预测钠钾合金热管运行特性的理论方法，为钠钾合金热管的合理充装及工程应用提供科学依据。在项目执行过程中，通过理论分析和实验研究发现，最优的钠钾合金充装量的多少与热源的空间覆盖范围有关，且当钠钾合金的液位高刚好充满热源覆盖范围内的热管容积时，启动迅速而且传热效果较好。应用以上研究工作摸索获得的钠钾合金热管充装量的设计经验，完成了自主设计制造的燃气轮机叶片/叶栅热管试件和充装量设计。经过试验验证，按照上述钠钾合金充装量设计经验研制的燃气轮机叶片/叶栅热管试件，在高温工况下启动成功，而且表现出良好的传热性能，能够发挥明显的热防护作用。