An Optimzation Of Wind Catcher Geometry in a Passive Downdraught Cooling Tower Using CFD

Abstract

The aims of the research work described in this paper is a part were to use computational fluid dynamics (CFD) to investigate the factors affecting the performance of a single-stage downdraught evaporative cooling device for low-energy cooling of buildings developed from a novel prototype device described by Pearlmutter et al. (1996; 2008); and to model and explore the performance of the device when integrated within a hypothetical building. This involved carrying out simulations: to select the most effective wind catcher geometry. Two types of wind catcher using curved deflector and closed cowl design were studied: In total five alternative arrangements were investigated. Arrangements 1 and 2 were bi-directional wind catchers. Arrangement 1 was modelled without a baffle and arrangement 2 was modelled with an extended baffle. Arrangements 3, 4 and 5 were unidirectional closed cowls. Arrangement 3 was modelled without a baffle, arrangement 4 was modelled

with

a short baffle and arrangement 5 was modelled with an extended baffle and an increased inner radius of 1 metre which had the effect of raising the mid-plane height of the cowl inlet by 1 metre. Initially, for comparison in all studies, the inlet wind speed was set at 10 m/s at a reference height of 11.5 metres which corresponded to the mid plane height of the wind catcher and wind cowl entry ducts for arrangements 1 to 4. All simulations were carried out using ANSYS CFX, versions 13.0, and the performances of the device were focused in selecting optimum air flow induced into the devices. The CFD simulations were carried out to define the optimum geometry of a wind catcher. Based on these simulation results, it was concluded that a uni-directional closed-cowl design was the most effective arrangement.