水平一维与二维单管外层流膜状凝结理论发展

Theoretical development of laminar film condensation on single horizontal tube with one-dimensional and two-dimensional surfaces

摘要:

在介绍水平光管外层流膜状凝结换热问题的Nusselt理论解的基础上,结合凝液受力分析,讨论了二维肋结构强化膜状凝结换热机理;介绍了表面张力所致压力梯度与淹没角建模方法的发展;介绍了典型二维表面低肋管外冷凝换热模型.综述分析表明:一维表面单管外的冷凝换热问题已有较为完善的理论求解模型;工业系列化的二维表面外的冷凝换热问题已有经验-理论求解模型体系;但各模型的一致性较差,二维表面冷凝换热模型应进一步考虑肋表面结构与粗糙度所致液膜曲率变化对凝结换热的影响.

Abstract:

Based on the introduction of Nusselt’s model,this paper reviewed the theoretical progress of lami-nar film condensation on single horizontal integral-finned tubes.Firstly,the Nusselt’s laminar film condensa-tion theory for single horizontal smooth tube and its experimental verification was introduced.Secondly,the mechanism of film condensation enhancement on two-dimensional(2D)surface was analyzed based on the stress analysis of condensation film that generated on the 2D fin surface.Finally,the vital models for film con-densation on 2D fined tubes and consistency check of them with experimental results were introduced in detail.The overview shows that the theoretical model for laminar film condensation on one-dimensional surface has been well established,and semi-empirical models for laminar film condensation on traditional 2D surface have been built up,but not yet completed.Effect of curvature change induced by 2D fin structure and the rough-ness of the fin surface on film condensation should be considered when more accurate semi-empirical model is needed.In order to complete the theoretical model for 2D surfaces and build theoretical model for 3D sur-faces,more efforts on mechanism analysis and accurate experiments should be made.