Numerical study of different ceiling-mounted air distribution systems for a virtual classroom environment

Abstract

This paper presents a comparative numerical study of different ceiling-mounted-localized air distribution systems placed above students in a virtual classroom in summer conditions. The influence of four different ceiling-mounted-localized air distribution systems, using vertical descendent jets, on the thermal comfort, local thermal discomfort, and air quality levels was numerically evaluated. The air distribution index, developed previously, was used for non-uniform environment. This index considers the thermal comfort level, air quality level, effectiveness for heat removal, and effectiveness for contaminant removal. Numerical simulations were conducted for a virtual classroom equipped with one of four different ceiling-mounted-localized air distribution systems and with 6 desks, 6 or 12 students, and 2 upper airflow outlets. Inlet air supply temperature of 20 and 24 C and an outdoor air temperature of 28 C were used. The simulation results show that the air supply system having a vertical air jet placed at 1.8 m above the floor level (Case III), and with an inlet area of 0.01 m 2 and a supply air velocity of 3 m/s would represent the best option in comparison with other air supply methods. In general, the air distribution index value decreases with an increase in inlet air temperature and the number of occupants. The air distribution index values are highest for Case III representing a classroom with 6 or 12 occupants with an inlet air temperature of 20 or 24 C.

Predicting the Air Quality, Thermal Comfort and Draught Risk for a Virtual Classroom with Desk-Type Personalized Ventilation Systems

“…In Conceição et al this numerical model was used to evaluate the environment in spaces equipped with mixing ventilation and cold radiant floor [26]; in Conceição et al the focus was on evaluating the influence of the descendent jets on the room occupants [27]; while in this work these numerical models are used to evaluate the influence of PVS on the occupants.…”

“…However, in Conceição et al it was adapted to be used for non-uniform environments of multi-occupation, in order to study spaces equipped with mixing ventilation and with cold radiant floor and occupied by two virtual manikins [26]. Also, Conceição et al evaluated several ceiling-mounted air distribution systems in a virtual classroom environment with six and twelve virtual manikins using the ADI concept for non-uniform environment [27].…”

A Review of CFD Analysis Methods for Personalized Ventilation (PV) in Indoor Built Environments

“…Note that this method does not include the thermoregulation model, and its reliability should be questioned when evaporation from skin is involved, but it has been shown to be in agreement with experimental studies and the ATC model [172]. In addition, the draft risk indicates the local draft discomfort at face exposure to the airflow from a PV nozzle [102,107,108], which has already been adopted in the ASHRAE and ISO thermal comfort standards [203,204]. The airflow interaction in the vicinity of the human body is complex and important, especially when PV nozzles supply fresh air to the breathing zone and penetrate the convective boundary layer around the body, so as to provide more acceptable inhaled air quality without draft complaints [205,206].…”

Energy Production of Solar DSF for Ceiling-Mounted Localized Air Distribution Systems in a Virtual Classroom

“…This kind of ventilation system is characterized by providing clean outside air directly to the body sections or breathing area of occupants at low air velocity and air turbulence intensity. It also allows occupants to control air temperature, airflow rate and airflow direction [22]. Some numerical and experimental works have been developed on this subject [22][23][24][25].…”

“…It also allows occupants to control air temperature, airflow rate and airflow direction [22]. Some numerical and experimental works have been developed on this subject [22][23][24][25]. Conceição et al [22] numerically compared the performance of four different ceilingmounted, localized air distribution ventilation systems using vertical descending jets placed above the occupants in a virtual classroom in order to optimize their positions inside the experimental classroom.…”