Effects of mass ratio of anhydrous methanol on frosting and defrosting performance of compact precooler
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摘要:
在主流来流的速度值、湿度值和温度值分别为10 m/s、6.4 g/kg 和50 ℃的实验条件下，对微管式紧凑型预冷器的结霜和抑霜性能进行了实验研究。在抑霜实验工况中，采用无水甲醇作为抑霜的有机溶剂，且在抑霜实验过程中喷射了三个不同质量比（0.75、1.0和1.25）的无水甲醇对预冷器进行抑霜。对不同实验工况的结霜和抑霜性能、压力损失系数、预冷器管束的壁面温度和预冷器的换热率进行了详细地分析。实验结果表明，在进行结霜实验时，当低温冷却剂流经预冷器的微细管束内部时，在预冷器的外侧会快速地凝结霜层， 且霜层随着实验时间的增长而逐渐累积。然而，一旦向主流来流中喷射了三个不同质量比的无水甲醇之后，会产生非常明显的抑霜效果，主流的压力损失系数显著下降且预冷器的换热率明显提高。此外，预冷器微细管束的壁面温度也显著的增大了，其壁面温度均高于水的冰点，这是喷射无水甲醇能够产生抑霜效果的直接原因。在向主流喷射三个不同质量比的无水甲醇的抑霜实验中，当喷射的无水甲醇的质量比为1.0时的抑霜效果最佳。此外，根据对抑霜实验结果进行分析，可以进一步地推测：实现最优抑霜性能的最佳无水甲醇质量比可能介于1.0～1.25之间。
Abstract:The frosting and defrosting performance of the microtubule compact precooler was studied under the experimental conditions of the flow velocity, the humidity value and the temperature of the main flow of 10 m/s, 6.4 g/kg and 50 ℃, respectively. Under the defrosting experimental conditions, anhydrous methanol was utilized as the solvent for defrosting, and anhydrous methanol with three different mass ratios (0.75, 1.0 and 1.25) was sprayed into the main flow for defrost the precooler during the defrosting experiments. The frosting and defrosting performance, the pressure loss coefficient, the wall surface temperature of the precooler tube bundles, and the heat transfer rate of the precooler were analyzed in detail. The experimental results revealed that when the cryogenic coolant flowed through the inside of the microtubule bundles of the precooler, the frost later quickly condensed on the outside of the precooler, and the frost layer gradually accumulated with the experimental time. However, once anhydrous methanol of three different mass ratios was sprayed into the main flow, the defrosting effect was obviously improved, the pressure loss coefficient of the main flow was significantly decreased and the heat transfer rate of the precooler was evidently increased. In addition, in the defrosting experiments, the wall surface temperatures of the precooler tube bundles were also significantly increased higher than the freezing point of water, making the spraying anhydrous methanol produce defrosting effect. Among three different mass ratios of the sprayed anhydrous methanol, the best defrosting performance was obtained when the mass ratio of the sprayed anhydrous methanol was 1.0. Moreover, based on analysis of the defrosting experimental results, it can be further inferred that the optimal mass ratio to achieve the best defrosting performance may be between 1.0 and 1.25.
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图 2 预冷器和实验段的三维装配图
Figure 2. Three-dimensional assembly drawing of the precooler and the experimental section
图 7 结霜和抑霜实验工况的压力损失系数分布曲线
Figure 7. Distribution curves of the pressure loss coefficient under the frosting and defrosting experimental conditions
图 8 结霜和抑霜实验工况的壁面温度分布情况
Figure 8. Distributions of wall surface temperature under the frosting and defrosting experimental conditions
图 9 结霜和抑霜实验工况的换热率分布曲线
Figure 9. Distribution curves of the heat transfer rate under the frosting and defrosting experimental conditions
表 1 紧凑型预冷器结霜和抑霜实验工况
Table 1. Frosting and defrosting experiment condition of compact precooler
实验工况
编号实验 主流
温度/℃主流速度/
(m/s)主流湿度/ (g/kg) 是否喷射
甲醇质量比Mr a-1 结霜 否 0 a-2 是 0.75 a-3 抑霜 50 10 6.4 是 1.0 a-4 是 1.25 
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