Comparison of various radiation-cooled dew condensers using computational fluid dynamics

Radiation-cooled dew water condensers can serve as a complementary potable water source. In order to enhance passive dew collection water yield, a Computational Fluid Dynamics (CFD) software, PHOENICS, was used to simulate several innovative condenser structures. The sky radiation is calculated for each of the geometries. Several types of condensers under typical meteorological conditions were investigated using their average radiating surface temperature. The simulations were compared with dew yield measurements from a 1 m(2) 30 degrees-inclined planar condenser used as a reference. A robust correlation between the condenser cooling ability and the corresponding dew yield was found. The following four shapes were studied: (1) a 7.3 m(2) funnel shape, whose best performance is for a cone half-angle of 60 degrees. Compared to the reference condenser, the cooling efficiency improved by 40%. (2) 0.16 m(2) flat planar condenser (another dew standard), giving a 35% lower efficiency than the 30 degrees 1 m(2) inclined reference condenser, (3) a 30 m(2) 30 degrees-inclined planar condenser (representing one side of a dew condensing roof), whose yield is the same as the reference collector, and (4) a 255 m(2) multi-ridge condenser at the ground surface provided results similar to the reference collector at wind speeds below 1.5 m s(-1) but about 40% higher yields at wind speeds above 1.5 m s(-1). (C) 2009 Elsevier B.V. All rights reserved.