Computational Fluid Dynamics study of a corrugated hollow cone for enhanced dew yield

Abstract

Dew condensation is the result of cooling by radiative deficit between a substrate and the atmosphere. Dew yield can be enhanced in hollow structures like hollow cones where the influence of wind is lowered. Corrugation increases the local tilt angle with horizontal and makes dew drop grow faster on edges, then drops detach sooner and act as natural wipers. However, corrugation increases the heat exchange with surrounding local air, which may reduce cooling.In order to evaluate these effects on cooling and dew yield, a corrugated, W-shaped hollow cone is compared to the same, smooth structure (S-cone) by Computational Fluid Dynamics. Two softwares were used: Ansys CFX for a pre-study concerning detailed aerodynamics where the computational domain is modeled to obtain a fully developed wind profile assuming an unobstructed inlet and COMSOL Multiphysics for aerodynamics coupled with heat flux, including radiative exchange surface-to-sky and surface-to-surface. Local temperatures can be obtained, which can be related to the dew yield. Turbulence is seen at all speeds but stagnation of the flow is also observed, which limits the convective heat exchanges and facilitates dew formation. At low wind speed, convective heat exchange is similar for both smooth and corrugated surfaces, and corrugation increases cooling. At higher air flow velocities, convective heat exchange is larger for the W-cone but cooling is only slightly smaller than found on the S-cone. Corrugated W-cone should thus give larger yield than the corresponding smooth S-cone.