Distribution of Air Flow Through a Green Wall Module

Abstract

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. The module is a rectangular plastic box (dimensions about 500 mm × 500 mm × 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 remove both gaseous and particulate pollutants from the air. Volatile Organic compounds (VOCs) and particulate matters PMs are both reduced by passing through the plant-growing medium, thus reducing the percentage of air flow that passes through the open top face of the module is essential to maximize the capacity of bio-filtration. 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 as well as air-flow rate through it have been obtained in a previous work [1], air-flow distribution through the module and the effect of introducing a cover to the module’s open top face are investigated in this work to improve the design of the module and achieve more appropriate flow rate and flow distribution. The top cover essentially includes small holes of 10 mm diameter to allow the necessary irrigation. The measurements help to determine the pattern of flow resistances which in turn will be used in a future CFD (Computational Fluid Dynamics) analysis.