Investigation Of Heat Transfer Mechanism Of Thin Film Evaporator

Working as a heat transfer equipment, refrigeration evaporator plays an important role in ships, chemical industry, aerospace field, etc. Thin film evaporation is an effective method for improving evaporator’s heat transfer effect due to its higher heat transfer performance. Heat and mass transfer mechanism research of thin film evaporation has already become a research hotspot in the domestic and overseas.This thesis proposes a mathematical model for thin film evaporation of evaporation tube in refrigeration evaporator based on Young-Laplace equation, influence factors of superheat, Hamaker constant A, surface tension as well as wall slip are taken into account in this model. The model is simplified and can be numerically solved. Results show that liquid flow and heat transfer are influenced by many factors in thin film area after this model is numerically solved. With the increase of superheat, the disjoining pressure gradient, the temperature jump of solid-liquid interface and the total heat transfer in thin film all increase; the whole liquid film shape becomes more smooth and total heat transfer decreases with the increase of Hamaker constant A; In non-evaporating region (adsorbed region), thin film is mainly controlled by disjoining pressure, surface tension has relatively small influence on this area. Liquid film becomes longer and thinner as surface tension increases, peak value of heat flux increases obviously. Total heat transfer isn’t influenced in the front of evaporation, after which total heat transfer increases; When the superheat is constant, the existence of wall slip boundary tend to cause the film thickness of thin film region to decrease. The heat flux and total heat transfer decrease as a result of the existence of wall slip boundary. The effect of wall slip boundary is larger with increasing superheat.A better understanding of the heat transport mechanisms in the thin film region of evaporation tube will directly help the designs of highly efficient evaporator and advanced thermal management systems. The numerical investigation presented in this report can be used as a theoretical direction to design a highly efficient thin-film refrigeration evaporator.