As an important component of the air-breathing combined precooling cycle engine of the hypersonic aircraft, the compact heat exchanger plays an important role in precooling the incoming air. However, the compact heat exchanger is easy to frosting during the precooling operation, which leads to an extremely unfavorable result, that is, the specific impulse and specific thrust of the engine significantly decrease. Therefore, in order to maintain the performance of the engine, some measures should be taken to defrosting the compact heat exchanger of the engine. In order to carried out the frosting and defrosting experiments on the compact heat exchanger that operating at relatively low altitudes, the frosting and defrosting performance of the compact heat exchanger are experimentally studied in the wind tunnel under the conditions of moderate airflow humidity value (6.4 g/kg), as well as the flow velocity and the temperature of the mainstream are 10 m/s and 50 °C, respectively. In the defrosting experiments, anhydrous methanol and anhydrous ethanol are sprayed into the mainstream as the defrosting solvents, respectively, and the mass ratios of anhydrous methanol to water and anhydrous ethanol to water are 0.75, 1.0 and 1.25. The experimental results indicate that for the frosting experiment, after coolant flows through the inside of the heat exchanger tube bundles, the frost layer quickly condenses on the outside of tube bundles. However, in the defrosting experiments, once a certain mass ratio of anhydrous methanol or anhydrous ethanol is sprayed into the main flow, the wall temperature of the heat exchanger tube bundles increases significantly, and the wall temperature is close to or higher than the freezing point of water. Furthermore, the defrosting effect and the heat transfer rate are obviously improved, and the pressure loss coefficient drops sharply. Through the analyzation of the defrosting experimental results, it is found that the defrosting performance of anhydrous methanol and anhydrous ethanol are obvious different, and the defrosting effect of anhydrous methanol is significantly higher than that of anhydrous ethanol with the same mass ratio. Within the range of experimental study parameters, for anhydrous methanol, the best defrosting performance can be obtained when the mass ratio is 1.0; and for anhydrous ethanol, the best defrosting effect can be realized when the mass ratio is 1.25. However, the defrosting performance of anhydrous ethanol with the mass ratio of 1.25 is still slightly lower than that of anhydrous methanol with the mass ratio of 0.75. Moreover, in order to achieve the best defrosting performance of the compact heat exchanger, the optimal mass ratio of anhydrous methanol to water may be in the range of between 1.0 and 1.25; and the optimal mass ratio of anhydrous ethanol to water should be greater than 1.25.

中文翻译：

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中等湿度条件下紧凑型换热器结霜与除霜性能实验研究

紧凑型换热器作为高超声速飞行器吸气式组合预冷循环发动机的重要组成部分，在进气预冷方面发挥着重要作用。然而，紧凑型换热器在预冷运行时容易结霜，从而导致极其不利的结果，即发动机的比冲和比推力显着下降。因此，为了保持发动机的性能，应采取一些措施对发动机的紧凑型热交换器进行除霜。为了对低海拔运行的紧凑型换热器进行结霜和除霜实验，在风洞中对紧凑型换热器在中等气流湿度值（6.4 g）条件下的结霜和除霜性能进行了实验研究。 /kg），主流流速为10 m/s，温度为50℃。除霜实验中，分别将无水甲醇和无水乙醇喷入主流作为除霜溶剂，无水甲醇与水、无水乙醇与水的质量比分别为0.75、1.0和1.25。实验结果表明，对于结霜实验，冷却剂流经换热器管束内部后，霜层很快在管束外部凝结。但在除霜实验中，一旦向主流中喷入一定质量比的无水甲醇或无水乙醇，换热器管束壁温明显升高，壁温接近或高于冰点。水。此外，除霜效果和传热速率明显提高，压力损失系数急剧下降。通过对除霜实验结果分析发现，无水甲醇和无水乙醇的除霜性能存在明显差异，且相同质量比下无水甲醇的除霜效果明显高于无水乙醇。在实验研究参数范围内，对于无水甲醇，质量比为1.0时可获得最佳除霜性能；对于无水乙醇，质量比为1.25时解冻效果最佳。但质量比为1.25的无水乙醇的除霜性能仍略低于质量比为0.75的无水甲醇。并且，为了使紧凑型换热器达到最佳的除霜性能，无水甲醇与水的最佳质量比可以在1.0～1.25之间。无水乙醇与水的最佳质量比应大于1.25。