Abrief state-of-the-art reviewis presented on research progress on dropwise condensation heat transfer in China. During the past 10 years, Chinese researchers have put forward some new proposals on the mechanism of dropwise condensation, and developed some new surface materials for promoting dropwise condensation. In particular, successful applications of dropwise condensation heat transfer surfaces in industrial condensers have provoked interest around the world and inspired the further investigation on the dropwise condensation. Since much of the work had been published in Chinese, it was considered appropriate to give a review in English. This review includes: (1) micro mechanisms and heat transfer characteristics for dropwise condensation; (2) methods for promoting dropwise condensation and (3) industrial applications of dropwise condensation.

The forces acting on a microcarrier or a small piece of tissue and its movement in the rotating wall vessel (RWV) bioreactor were analyzed. The tracks of a particle in RWV reactor were calculated under different inner and outer cylinder wall rotating speeds, different particle sizes and different density difference between culture medium and the particle. The results show that cells or particles experience partial microgravity only in the upper area ofRWV, which changes with angle θ, while in the lower part ofRWV, they experience overweight. The trajectory of a moving particle in RWV reactor is an eccentric helix under ground-based condition. And the eccentric degree increases with the decrease of outer wall rotating speed, and with the increase of density difference and particle size. The proper match of rotating speeds of inner and outer cylinder walls is the key to prevent the particle colliding with the walls. For a relatively large piece of cultivated tissue, it can move around the inner wall only when the rotating speed of the outer cylinder is high. And the drag force acting on a particle inside RWV increases with the particle size and the density difference.

Considering the liquid transverse suction effect at the porous layer interface, a mathematical model was presented to investigate the influence of the porous layer characteristic parameters on condensation heat transfer. The results revealed that the enhancement ratio increased with the increase of the porous layer thickness and permeability. The effective thermal conductivity of the porous layer was, however, of little significance for condensation heat transfer enhancement. Also, the enhancement mechanism was analyzed by comparing the thermal resistances within the external condensate film and the porous layer.

Film condensation on a vertical porous coated plate is investigated numerically for a porous/fluid composite system based on the dispersion effect in the porous coating. The mathematical model improves the conventional matching conditions by considering the stress force at the porous coating interface. The numerical results show the ef-fects of the porous coating thickness, the effective thermal conductivity and the permeability on condensate film thickness and local Nusselt number. The predicted average Nusselt number has similar tendencies to experimental results reported in iterature, such that using a thin porous coating would be a viable alternative for enhancing the condensation heat transfer.

The effect of processing conditions of polymer film on dropwise condensation heat transfer of steam under atmo-spheric pressure is investigated to find an effective technique to prepare a viable polymer film sustaining long-term dropwise condensation pattern state. The polytetrafluoroethylene (PTFE) films were coated on the external surfaces of brass tubes, copper tube, stainless steel tube and carbon steel tube by means of the dynamic ion-beam mixed implantation technique, with a variety of surface processing conditions. The experimental results indicated that heat flux is increased by 0:3-4:6 times and condensation heat transfer coefficient by 1:6-28:6 times of film condensation values for the brass tubes treated with various conditions. The surface processing condition is crucial to the adhesion between polymer film and metal substrate, different substrate material requires different optimal processing condition, and leads to different condensation heat transfer characteristic.