Performance Enhancement of Falling Film Dehumidifier by Variation Number and Width Ratio Rectangular Cylinder Based on CFD Simulation

Abstract

The implementation of computational fluid dynamics (CFD) technologies has grown popular in various engineering fields to solve problems because it has high efficiency, affordable cost, and requires a relatively short time. This study examines the effect of adding a rectangular cylinder to a falling film dehumidifier with modifications to the geometry of the width ratio and the number of rectangular cylinders. Model without rectangular cylinder variations and three width ratio variations of 0.1D; 0.5D; D with two variations of the number of rectangular cylinders will be simulated under isothermal conditions for the process of mass transfer, distribution of water vapor mass fraction, pressure drop, turbulence intensity, temperature, and dehumidifier performance. The RNG k-ε turbulence model is used to simulate fluid flow with the addition of a user-defined function (UDF). Significant results can be seen in the distribution of water vapor mass fraction in the geometry modification with the addition of a rectangular cylinder with mass transfer enhancement of 12.4 – 13.4% compared to no geometry modification. High Wa,in with variation C is more effective in minimizing the pressure drop of moist airflow. Vortex flow is formed behind the rectangular cylinder, which increases the mass transfer around the flow. The turbulence intensity appears near the liquid desiccant solution and the rectangular cylinder with a value of 33%. The best geometry variation design shows a dehumidification effectiveness value of 36.8%, 3.3 – 3.8% greater than the design without geometry variations.