Aerodynamic analysis and CFD simulation of several cellulose evaporative cooling pads used in Mediterranean greenhouses

The present work makes an aerodynamic analysis and computational fluid dynamics (CFD) simulation of the four commercial models of corrugated cellulose evaporative cooling pads that are most widely used in Mediterranean greenhouses. The geometric characteristics of the pads have been determined as well as the volume of water they retain at different flows of water, thus obtaining the mean thickness of the sheet of water which runs down them and their porosity. By means of low velocity wind tunnel experiments, the pressure drop produced by the pads has been recorded at different wind speeds and water flows. In this way it has been possible to obtain the relationship of the permeability and the inertial factor with pad porosity using a cubic type equation. Finally, a CFD simulation with a 3D model has been carried out for both dry pads (Qw = 0 l s−1 m−2) and wet ones (Qw = 0.256 l s−1 m−2), finding good correlation between the simulated and experimental pressure drop, with maximum differences of 9.08% for dry pads and 15.53% for wet ones at an airspeed of 3 m s−1.

Research highlights
► Modeling of evaporative pads using CFD proves to be a good tool for optimizing their design.
► Comparison of simulated and experimental pressure drop values shows a good degree of agreement.
► At higher water flow the pressure drop produced by the pad increases, but to a lesser extent than at higher air flow.
► Good degree of agreement has been found between porosity and both the water flow applied and the pad geometry.