A Numerical Study for Coating of Ventilation Ducts Using Jet Injection

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In this study, the performance of a novel method where an antibacterial solution is pressurized and sprayed into recirculated air through nozzles, is investigated numerically. This resembles a jet in a cross-flow problem where the antibacterial solution mixes with ventilation air and further adheres to the inner surfaces of the duct. The motion of particles dispersed in antibacterial solution is described as the advection of a passive scalar, i.e., temperature, allowing for a single-phase flow solution. The effectiveness of the coating is evaluated by the temperature distribution on the inner surfaces of the duct. Single phase 3-D turbulent flow of air at two different temperatures is modeled and the velocity and temperature fields in the ventilation duct were calculated using the commercial code ANSYS FLUENT. The numerical model is validated by experiments conducted on a full-scale test rig, in terms of temperature. The numerical calculations were conducted in four series: where the effect of the nozzle arrangement, the jet injection angle, the jet-to-cross-flow velocity ratio, and a time-dependent jet velocity profile of a sinusoidal wave form are investigated. The numerical solutions show that the coating is highly inefficient for velocity ratios less than 3.3, and the period of time-varying jet stream has little effect on the coating performance.