Measurement of air flow through a green-wall module

© 2006 Australasian Fluid Mechanics Society. All rights reserved. Green or living walls are active bio-filters developed to enhance air quality. Often, these walls form the base from which plants are grown; and the plant-wall system helps to remove both gaseous and particulate air pollutants. A green wall can be found indoors as well as outdoors, and could be assembled from modules in an arrangement similar to tiling. Measurement of air flow through such a module has been conducted in this work. The module is essentially a rectangular plastic box (dimensions about 500 mm x 500 mm x 130 mm) that holds a permeable bag containing a plant-growing medium (replacement for soil). The front face of the module has multiple openings for plants to protrude out from the bag inside. Plant roots are imbedded in the medium. A fan positioned at a central opening on the module‟s back face drives air through the medium-plant-roots mix and then onward through the plants‟ canopy; and these would help to remove both gaseous and particulate pollutants from the air. Drip-irrigation water is dispensed from a tube running along the open top-face of the module. The module has also a small drainage hole on its bottom face. Pressure drop across the module, air-flow distribution through it as well as flow rate have been obtained, in terms of variable parameters which include moisture content, growing-medium-plant-roots mix and plant type. The measurements help to determine the pattern of flow resistances which in turn will be used in a future CFD (Computational Fluid Dynamics) analysis for improving the design of the module, such that more appropriate flow distribution and flow rate would be achieved. All this is in addition to the better understanding of air flow through complex moist porous media.