Experimental investigation of water vapor condensation from hot humidified air in serpentine heat exchanger

Condensing economizers are used in industry and power plants for waste heat recovery. Despite widespread use, their thermal design is still not optimized due to the complexity of the condensation process especially when non condensing gasses are prevalent. This paper presents an experimental study of water vapor condensation on the vertical tubes of a serpentine bundle in a humidified air crossflow at water vapor mass fractions of 10% and 20%. The analysis showed a clear dependence of the efficiency of the condensation process on the humidified air inlet temperature and Reynolds number, and the efficiency increases as these parameters decrease. Condensation efficiency also depends highly on flow humidity especially in the region of higher Reynolds numbers. A comparison of the average Nusselt number in the case of dry air with the experimentally determined average Nusselt number is also presented, and showed a uniform increase in the Nusselt number as the inlet temperature of the humidified air decreased.