Experimental study of initial frost surface coverage characteristics on cryogenic cold surfaces under natural convection

Abstract

Experimental investigations of frost formation initial stage on vertical cold plate surface under the conditions of natural convection reveal distinct growth patterns of initial frost crystals across temperatures ranging from −50 ℃ to −190 ℃. Frosting mechanism is significantly influenced by the cold plate temperature, which changes from the cold surface condensation/desublimation to the boundary layer condensation/desublimation as cold plate temperatures decrease. Correspondingly, frost crystal growth characteristics under different frost mechanisms are also different, which are first reflected in the frost formation initial stage. The effects of cold plate temperatures especially lower than −100 ℃ as well as the environmental parameters on the frost crystal coverage was focused. It has been discovered that frost crystal coverage increases as cold plate temperature drops from −50 ℃ to −100 ℃. Similarly, the rate of frost crystal coverage increases significantly first with air temperature and relative humidity, after that their influence weakens with higher air values. However, at lower temperatures from −100 ℃ to −170 ℃, frost crystal coverage decreases with further cooling, while air temperature and relative humidity exhibit negligible influence on early frost formation, with their effects weakening progressively at colder conditions. Changes in the frost formation mechanism are the primary reason for this phenomenon. This paper can enhance the comprehension of the frost formation initial stage and provide a reference for defrosting and frost suppression on cryogenic surfaces.