The use of heavy fluids (typically refrigerants) for tests on turbomachinery equipment, like centrifugal compressors, under similitude with real working conditions is a common practice in the test facilities of manufacturers. This practice leads to the release of the test gas to the environment, mainly coming from seals, test circuit connections, valve gaskets and from operations of circuit assembling/disassembling necessary to replace or service the machine under test.

The spatial distribution and flow of these emissions inside the test building is a complex issue, which depends on the specific circuit features, location of sources, geometry and openings of the building and variable climatic conditions of the location. For a preliminary assessment of the health and safety conditions, a NIST computational package — including a CFD solver — was applied. The aim was to validate the applicability and reliability of this tool, which was developed for other types of buildings; from the industrial side, knowledge of the diffusion scenario is important to define test protocols to guarantee acceptable emissions levels for manpower in working areas.

The industrial building is organized in multiple inside workspaces. The concentration of the contaminant in the area of the test benches, determined by the internal fluid dynamics, is calculated with the CFD solver included in the NIST package. In the building, air motion is only affected by natural ventilation. For this reason, the interactions between the outside and the interior climatic and microclimatic parameters must be considered, taking into account also the different possible assumptions about the daily management of the openings of the building envelope. Several cases of release and dispersion of heavy fluid inside the working areas, under different boundary conditions, were considered. The sensitivity of the results to the different seasonal conditions was assessed and discussed. The complex internal geometry of the building was simulated by a combination of single zone models. The results showed an expectable presence of test gas emissions in the neighborhood of the test area and the possibility of buoyancy effects within the large building. A relatively stable concentration of the test gas emissions resulted from the application of the model, which was affected only by substantial variations of the climatic conditions.

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