Experimental assessment of mass transfer characteristics of polypropylene surfaces for low flow falling film liquid desiccant air-conditioning applications

Corrosion problem of metallic surfaces has resulted in a bottleneck situation deterring widespread acceptability of liquid desiccant air conditioning systems. In the current experimental study, mass transfer analysis of noncorrosive polypropylene plastic surfaces, Plain and Modified solid circular cylinders, are investigated on an adiabatic vertical falling film tower. The performance of the vertical solid PP circular cylinder surfaces is compared with PP plate surface to deduct suitable surface for the development of low flow liquid desiccant air conditioning systems. It is found that under the tested conditions, the mass transfer coefficient of the Plain PP circular cylinder is 1.65 times superior to Plain PP plate. The optimal mass transfer coefficient of -20 g/m2s for the Plain PP circular cylinder is obtained at -1.5 ratio of the mass flow rate of liquid to air, whereas the mass transfer coefficient of the Modified PP circular cylinder continuously increases for the studied range of the mass flow rate of liquid to air ratio. Furthermore, a new generalized correlation for Sherwood number is proposed to predict the performance of different types of falling film towers (plastic/metallic) under adiabatic/non-adiabatic operating conditions by incorporating dynamic flow characteristics, driving thermal and mass transfer potential and wetness characteristic factor. The mean effective error of the current correlation against nine experimental datasets is 16.6%.