Investigation into air distribution systems and thermal environment control in chilled food processing facilities

Air flow distribution in chilled food facilities plays a critical role not only in maintaining the required food products temperature but also because of its impact on the facility energy consumption and CO2 emissions. This paper presents an investigation of the thermal environment in existing food manufacturing facilities, with different air distribution systems including supply/return diffusers and fabric ducts, by means of both in-situ measurements and 3D CFD simulations. Measurements and CFD simulations showed that the fabric duct provides a better environment in the processing area in terms of even and low air flow if compared to that with the diffusers. Moreover, temperature stratification was identified as a key factor to be improved to reduce the energy use for the space cooling. Further modelling proved that air temperature stratification improves by relocating the fabric ducts at a medium level. This resulted in a temperature gradient increase up to 4.1 °C in the unoccupied zone

Numerical and experimental study of the International Space Station crew quarters ventilation

International audienceThe current paper proposes a detailed study of the ventilation system of the crew quarters (CQ) aboard the International Space Station (ISS) in order to identify the ventilation system's capacity to reduce CO2 accumulation around an occupant. These results would enable the improvement of the ventilation system, thereby decreasing the health risks of the occupants. The ventilation flow fields are studied through numerical results which are validated with experimental Particle Image Velocimetry (PIV) measurements in a reduced-scale mock-up. The equivalence between the reduced scale experimental and the full-scale numerical results is obtained through a Reynolds-number based similitude criteria. This enabled the authors to validate the isothermal airflow in the full-scale numerical model with the experimental results of the water flow in the reduced-scale mock-up. Normalized numerical and experimental velocity profiles have been superposed and were found to be in good agreement. Both numerical and experimental models highlight a stagnation region in the centre of the CQ volume leading to a ventilation deficit of the astronaut's breathing zone. The results indicate that this stagnant region is a reason for the excess CO2 accumulation in the CQ, despite the high ventilation rate (>45 hourly air exchanges). To the author's best knowledge this is the first numerical study of the CQ ventilation system validated with reduced-scale experimental modelling. The paper's findings have implications in building air quality studies, suggesting that targeted ventilation is preferable to raw increased in flow rates