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.

This paper reports the test results of the first industrial-scale absorption heat transformer (AHT) equipment in China, to recover the waste heat released from mixture of steam and organic vapor at 98 C in coacervation section, synthetic rubber plant of Yanshan Petrochemical Corporation, Beijing, China. The recovered heat is used to heat hot water from 95 to 110 C, feeding back to the coagulator as the supplementary heating source. The AHT system is operating with H2O/LiBr solution with heat flow of 5000kW. The coefficient of performance (COP), the thermal efficiency and the temperature lift of the AHT system are presented. The heat transfer characteristics of the AHT components, i.e. absorber, generator, evaporator, condenser and the liquid-liquid solution heat exchanger, are also illustrated by comparison of experimental data and the model calculated results. The results show that the mean COP is 0.47, the gross temperature lift of 25 C can be realized and the payback period is 2 years.

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.

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 present paper reports an experimental investigation of film condensation in a vertical, internally finned tube with a wire insert. The finned tube and wire insert were chosen as the best performing from a series of tubes and inserts tested separately in previous investigations. Compared with previous results for the finned tube, it was found that only for ∆T>10K did the addition of the insert somewhat improve the heat transfer performance. However, the pressure drop for the finned tube with insert was increased. Empirical correlations for friction factors for the three tube configurations are proposed based on the present data.