Experimental Study on the Aerodynamic Sealing of Air Curtains

Abstract

Abstract:Controlling the air quality is of the utmost importance in today's buildings. Vertical air curtains are often used to separate two different climatic zones with a view to reduce heat transfer. In fact, this research work proposes an air curtain aimed to ensure a proper separation between two zones, a clean one and a contaminated one. The methodology of this research includes: (i) small-scale tests on water models to ensure that the contamination does not pass through the air curtain, and (ii) an analytical development integrating the main physical characteristics of plane jets. In the solution developed, the airflow is extracted from the contaminated compartment to reduce the curtain airflow rejected to the exterior of the compartment. In this research work, it was possible to determine the minimum exhaust flow necessary to ensure the aerodynamic sealing of the air curtain. This article addresses the methodology used to perform the small-scale water tests and the corresponding results.

Full-size experimental assessment of the aerodynamic sealing of air curtains for particulate matter

“…That is to say, a plane jet that ensures minimum (optimized) exhaust flowrates from the contaminated compartment or that supplies minimum (optimized) flowrates to the non-contaminated compartment, and ultimately reduces the air treatment costs. This research encompasses three phases, namely: (i) small-scale experiments using water as the work fluid 10 ; (ii) computational fluid dynamics (CFD) simulations to verify if the small-scale test results are applicable to full size air curtains 11 ; and (iii) full-size air curtain experiments. The full-size experiments were subdivided in two sets of tests, namely: (iiia) assessment of the aerodynamic sealing for PM10 and comparison with the visual assessment and (iiib) optimisation of the aerodynamic sealing.…”

“…Therefore, in the scope of this project it was necessary to develop the research on the isothermal case, which is considered a limit condition. Previous isothermal work, carried out in the framework of this project, showed that the aerodynamic sealing could be obtained on a small-scale test rig 10 and the corresponding physical laws were developed. It was also shown, by Computational Fluid Dynamics (CFD), that this aerodynamic sealing could be expected for full-size applications.…”

“…The approach described below was adopted: It was considered that the physics of the case of the “contaminated” compartment, presented in Figure 1(a), is relevant for this study. The results from previous research conducted for the isothermal case 10,11 were considered. The ratio between external and internal concentration of PM10 and PM2.5 for different air curtain working parameters (jet nozzle angle and velocity) has been studied in ‘Particulate matter concentration measurement tests’ section to demonstrate that: The air curtain presents a good aerodynamic sealing for the particulate of PM10 and PM2.5 classes. The minimum air exhaust rate from the compartment to obtain the aerodynamic sealing is similar when the assessment is carried out using the ratio between external and internal concentration of PM10 and PM2.5 or when using a visual assessment. As the typical size of bacteria ranges from 0.5 µm to 5 µm and it can be associated with the corresponding size particles, in the scope of this work the aerodynamic sealing of the curtain for bacteria is analysed as an aerodynamic sealing of PM 10 particulate. …”

Full-Size Experimental Assessment of the Aerodynamic Sealing of Low Velocity Air Curtains

“…To avoid the transport of airborne pollutants (which, in general, may include microorganisms, bacteria, fungus, particles), the air is extracted from the contaminated compartment, which induces a flow crossing the air curtain. This behaviour, in specific conditions, may avoid the flow to be released from the contaminated compartment to the non-contaminated side at the jet impinging zone, as shown in Figure 1 (see Section 2.1 of reference [26] for a more detailed analysis). The air extracted from the contaminated compartment should be decontaminated.…”

“…To obtain the exhaust flow rate that provides aerodynamic sealing under different air curtain characteristics, a research program was established, consisting of the following phases: (i) small-scale experiments using water as the work fluid [26]; (ii) Computational Fluid Dynamics (CFD) simulations to verify if the small-scale test results were applicable to a full-size air curtains [28]; (iii) full-size air curtain experiments. The full-size experiments were subdivided into two sets of tests, namely: (iiia) assessment of the aerodynamic sealing for PM10 and comparison with the visual assessment [27] and (iiib) optimisation of the aerodynamic sealing for low Reynolds number jet velocities.…”