In this paper, the airflow characteristics in the outlet region of a generic vortex diffuser are experimentally and numerically investigated. A specific arrangement of tetrahedral and hexahedral cells was used in grid generation: it has been found ideal for the analysis of the room air movement due to an air diffuser.
Corresponding airflow measurements were conducted by using a three dimensional ultrasonic anemometer.
Seven air supply and return diffusion layouts were tested to determine their effects on air distribution, air change efficiency and ventilation efficiency for workstations in an open-plan office. This document describes and comments the results of these measurements.
From experimental data on eight common air diffusers, authors developed simplified methods (the box method and the momentum method) to describe air flow and temperatures in the air jet that can be used as imput data for room air flow CFD calculations. The box method is appropriate for most of the diffusers. The momentum method gives good results for five diffusers. As it is simpler, authors recommend that it is used whenever applicable.
Part 1 of this paper gives first an outline of the experiment (full-scale measurement of the air velocity carried under isothermal condition), then discusses the 2 modeling methods - the BOX method and the P.V. method - used for CFD simulation.The results of calculations with the 2 methods showed good agreement with the experimental data.
A thermal manikin with a simulated lung was placed in an air-conditioned office with fresh air supplied in close proximity to the facial area at flow rates from 0.1 to 2 l/s. CO2 concentration measurements allow to define the fresh air utilization efficiency and the pollutant exposuer reduction efficiency.
The impact on thermal comfort of the way of introducing replacement air (to replace air being exhausted by the hood) in a kitchen was analysed using mathematical models and laboratory experiments with a tyhermal mannequin. Results allow to rank systems for replacement air introduction from the most to the least tolerable : displacement ventilation, mixing ventilation with ceiling air diffusers, front-face discharge and backdrop plenum.
This study compares indoor climate, cooling efficiency and energy consumption of an underfloor air distribution system and a ceiling-based system in a test chamber. Floor-based system appears to provide better thermal conditions with lower electricity consumption.
CFD calculations were used to compare temperature and air velocities in an environmental chamber equipped either with a conventional comfort overhead air supply system or with an underfloor supply system. Results show the advantages of underfloor system to provide adequate temperature, velocities and turbulence in the seated zone.