Experimental study of local effectiveness in the case of balanced mechanical ventilation in small offices

Abstract

In this paper different mechanical ventilation methods were analysed in a test room, having similar dimensions with a small office room. A series of measurements were performed with mixing, displacement and personalized isothermal ventilation having one or two occupants in the room. The main goal of this research was to investigate the air cleaning performance of different ventilation strategies in the breathing zone. The CO2 emission of involved persons was determined and it was shown that one person released 13.4 l/h CO2 while two persons released 23.63 l/h CO2. Taking into account the spread of viruses and the requirements related to separation of persons in public buildings, measurements were carried out with “open” working desk and with “screened” desk as well. Using the balance equation of pollutants, the equation which describes the CO2 concentration variation in the closed space was developed and used for calculations. Air flow visualization was done for different ventilation modes. The local ventilation effectiveness was determined for each ventilation mode based on the measured and calculated CO2 concentrations depending on the provided fresh air flow, air distribution and occupants number. In the case of screened desk the personalized ventilation shows the highest local effectiveness (1.6–2.7 in comparison with 0.6–1.4 in the case of mixing and displacement ventilation).