Ventilation performance measurement of a decentralized mechanical system with heat recovery using tracer gas decay method

In decentralized mechanical ventilation, air supply being very close to exhaust, short-circuiting of the supply air towards the extraction point may occur, increasing energy consumption of the system and decreasing air diffusion quality. To estimate this quality together with thermal comfort, we measured in a climatic chamber effectiveness of a local ventilation prototype using tracer gas decay method, as well as air velocity.
The results show that air change efficiencies, are higher than 0.5 for 50%, 80%, 100% ventilation regimes, and fluctuate between 0.41 and 0.43 for 20% one. Local air change indexes are higher than 1 for regimes higher than 50%, and lower than 0.89 for 20% one. All measured velocities are lower than 0.08m/s. We conclude that the prototype achieves an acceptable air diffusion quality for nominal ventilation regime. But it is not acceptable under 20%. Measurements of velocities do not show any thermal discomfort.