The corrosion problem of liquid desiccants hampers the development of liquid desiccant-based air-conditioning systems. Plastic surfaces can be a promising alternative because of their anti-corrosive property. However, plastic has the inherent problem of low wettability. The present experimental study investigated the regeneration performance of a liquid desiccant over multi-inline vertical polypropylene circular cylinder surfaces in an adiabatic mode, to find a substitute of vertical plate surfaces for developing low flow falling film towers. The mechanical surface modification method was explored to elevate the performance level of the circular cylinder surface. A comparative performance analysis was conducted between the circular cylinder and plate surface. It was found that the regeneration rate of the Conventional circular cylinder surface was superior to the Conventional plate surface by 50.5% for the evaluated conditions. The regeneration rate of the circular cylinder surface can reach up to 0.684 g/s at a 2.5 mass flow rate ratio of the solution to air. A new generalized empirical correlation was proposed to estimate the effectiveness of falling film regenerators by incorporating the driving potential of heat and mass transfer process and wetness parameters. The prediction accuracy of the present correlation was 16.5% (i.e. mean effective percentage error) against nine datasets. The outcome of the present study would be beneficial for developing low-flow solar-assisted plastic falling film liquid desiccant regenerators.