Experimental and theoretical investigation on transportation of gaseous pollutants in long and narrow industrial buildings

Abstract

Controlling the escape of industrial pollutants in large spaces often consumes a lot of energy. General ventilation is widely adopted as a significant control method. The design foundation of a general ventilation system with high efficiency and low consumption is to grasp the transport characteristics of pollutants in large spaces. However, little is known about that inside a long and narrow industrial plant, as one kind of typical large space. This paper conducts a water tank experimental platform for re-scale test to compare the characteristics of pollutants transportation in a long and narrow industrial building and a traditional industrial building with different source temperature, and is supplemented with theoretical derivation. Results show that with increasing ratio of ventilation rate G and polluted flow rate at the exhaust height Lp (G/Lp), the flow pattern of polluted flow within the factory gradually changes from the “Back-mixing” flow pattern when G/Lp<1 to “One-way” flow pattern when G/Lp>1. With increasing buoyancy 1/Fr, the “Back-mixing” flow pattern can be divided into complete and partial “Back-mixing” stages at 1/Fr=0. The “One-way” flow pattern can be divided into coarse top-level and smooth top-level stages at Frc. According to the dimensional analysis method, the critical Froude number Frc for the “One-way” flow pattern that reaches the smooth top-level stage is just related to the height coefficient of the plant H/D and the flow coefficient of the plant G/u0D2. The existence possibility and the theoretical condition of the “One-way” to “Back-mixing” flow pattern is deduced, in which there will be one or more circulation cells in the lower indoor space.