Frosting characteristic on the cold irregular surface under high temperature environmental conditions

Frost formation on the air side of the heat exchange channels of the precooler has an important effect on the overall performance of the precooled engine. Condensation/frosting process of three kinds of specimens with irregular surface topography structure (Ra=0.97 μm, Ra=1.78 μm, Ra=1.92 μm) in high temperature environment (T_a=50 ℃) was studied experimentally. The effect of the ambient temperature (T_a is 50 ℃ and 18 ℃), surface temperature (T_w is -10.9 ℃, -23.0 ℃, -28.0 ℃) and the irregular surface structure on frost crystal/condense droplet growth characteristic were studied. The densification mechanism of the frost layer was summarized and analyzed. The experimental results showed that the higher the ambient temperature, the lower the surface temperature, and the shorter the frost crystal growth cycle. On the surface of the three specimens, the closer to the edge of the specimen, the earlier the condensation droplets appeared and the faster it grew. Besides, it was also found that the surface morphology and structure have influence on the whole process of droplet condensation and frost layer growth. The mechanism of the surface topography structure on condensation was preliminary analyzed, but the mechanism of irregular surface topography structure on frost growth needs further study.