Tests of localized ventilation systems in a new controlled environment chamber.

This paper describes tests of thermal and ventilation performance of two relatively new occupant-controlled localized thermal distribution (also called task ventilation) systems. The first is a raised-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. These systems have been tested 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 control and range of occupant comfort levels produced in the local workstation. The results are also compared to those produced by a conventional ceiling supply system. 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. The CEC closely resembles a contemporary office space 5.5 m x 5.5 m x 2.5 m in size, with exterior windows on two walls and reconfigurable HVAC and lighting systems. Air can be supplied and returned from floor or ceiling levels, the surface temperature of the windows controlled by air circulated through the triple-pane glazing, and two separately controlled air supplies can be provided to the space simultaneously. The tests investigated the effects of supply volume, supply location, supply vent orientation, supplylreturn 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 velocities in the vicinity of outlets could exceed 3 m/s . Such wide-ranging values could violate existing comfort standards, if strictly interpreted. However, since these systems put the local thermal conditions within the workstations under the direct control of their occupants, it is likely that the standards should grant exceptions to such systems.