Testing of Localized Ventilation Systems in a New Controlled Environment Chamber

Abstract

This paper describes tests of thermal comfort and air distribution performance of two relatively new occupant‐controlled localized ventilation (also called task ventilation) systems. The first is a raisd‐floor distribution system providing air through grilles in the floor panels, and the second is a desk‐mounted unit supplying conditioned air at desktop level. The tests were performed in a new controlled environment chamber (CEC) having unique capabilities for detailed studies of space conditioning and thermal comfort in office environments. Measurements were made in a mockup of a typical partitioned open‐plan office, and the resulting temperature and air velocity distributions are reported for a variety of system‐ and locally controlled conditions. Comfort model predictions are presented to describe the degree of environmental control and range of occupant comfort levels produced in the workstations. The results are also compared to those produced by a conventional ceiling supply system. The tests investigated the effects of supply volume, supply location, supply vent orientation, supply/return temperature difference, heat load density, and workstation size and layout. Temperature differences in the range of 1–2.5°C were observed between adjacent workstations, and local air velocities in the vicinity of outlets could exceed 3 m/s. Such wide‐ranging values could violate existing comfort standards (ASHRAE, 1981; ISO, 1984), if strictly interpreted. However since these systems put the local thermal conditions within the workstations under the direct control of their occupants, it is recommended that the standards grant exceptions to such systems.

Airflow and air temperature distribution in the occupied region of an underfloor ventilation system

“…From the above results, it can be seen that under the tested supply air conditions and heat loads, the air temperature stratiÿcations were kept within the suggested comfort criteria. Although previous research (such as Akimoto et al [4] and Arens et al [9]) showed that the oor-based ventilation systems have a higher possibility that uncomfortable temperature stratiÿcation will be created in the room, our results reveal that with proper design of the supply air conditions, the temperature stratiÿcation can be maintained at a comfortable level in a FR-type under oor ventilation system.…”

“…Akimoto et al [4] indicated that thermal stratiÿcation was observed in a oor-supply displacement ventilation system. Experiments conducted by Arens and co-workers [9] also revealed the draught discomfort and temperature stratiÿcation problems associated with the oor-based ventilation systems.…”

Sensation of draft at uncovered ankles for women exposed to displacement ventilation and underfloor air distribution systems

“…Schiavon The CBE climate chamber ( Figure 1A) measures 5.5 m × 5.5 m × 2.5 m, and features controlled air temperature to an accuracy of ±0.5 °C and controlled relative humidity to ±3%. The chamber is described in detail by Arens et al [31]. The chamber is configured to appear as a realistic office, so as to attenuate the psychological influence of being a human subject in a laboratory experiment.…”

Introduction of a Cooling-Fan Efficiency Index

“…The use of cooling fans in practice is easy and does not require special installations. The personalized ventilation systems (Melikov 2004) and the task-ambient conditioning systems (Arens et al 1991;Bauman et al 1998) perform better with regard to thermal comfort, since they may operate under nonisothermal conditions (i.e., the supplied air can be cooled below the room air temperature in addition to elevated velocity). Appearance, power consumption, and price are the main parameters considered when purchasing cooling fans, while cooling capacity and efficiency of energy use are unknown.…”