Study on the anti-frosting performance of hydrophobic fin with non-toxic for the R600a frost-free refrigerator

Abstract

The finned-tube evaporator (FTE) is widely used for the freeze and cold storage (FCS) system, such as R600a frost-free refrigerator, R290 household air-conditioning, and R717 walk-in cold stores, but it has problems of low defrosting efficiency and high electric heater consumption at the low evaporating temperature. The traditional super-hydrophobic aluminum-based fin (SAF) has a good the frost retarded performance. However, the SAF is usually fabricated by the wet chemical etching, and is not suitable for FTE with non-toxic of the R600a frost-free refrigerator in the future. Meanwhile, the traditional SAF tested and fabricated has the high-cost and complicated manufacturing method. To address these issues, a novel SAF with non-toxic (surface contact angle is 151.8°) is fabricated in this paper, by the stearic acid solution on the aluminum square laser engraved, and used to improve the anti-frosting performance of the FTE for the R600a frost-free refrigerator under low temperature conditions. The anti-frosting performance should be assessed before applying the non-toxic super-hydrophobic to the FCS system. Meanwhile, there are few theoretical and experimental studies about the SAF on restraining frost formation for the FCS system, especially in the field of computational fluid dynamics (CFD) currently. Thus, a three-dimensional frosting numerical model based on the Euler multiphase flow is developed to analyze the frost formation and distribution characteristics on the SAF with non-toxic, and the numerical model has been validated by experimental date. The experimental and numerical analysis methods are used to evaluate anti-frosting performance of FTE and comparisons with the hydrophilic aluminum-based fin (surface contact angle is 8.6°) and bare aluminum-based fin (surface contact angle is 92.4°) are also discussed. The experimental results indicate that the frosting time of 240 min, and the frost thickness of the FAS with non-toxic is reduced by 41.56% and 38.25% compared to BAS and HAS, respectively. The FAS with non-toxic has a more significant effect on frost formation retarded on the cold surface compared to the HAS. In addition, the proposed frosting model predicts frost growth process, the frost temperature distribution, the moist air velocity distribution, and the frost density distribution on the SAF cold surface. This study, not only reaffirms the benefit of using the SAF with non-toxic on restraining frost formation for the FCS system, but also provides some rules of the frost growth and distribution characteristics with different factors.