JET DROP MODELS FOR CONTROL OF NON-ISOTHERMAL FREE JETS IN A SIDE-WALL MULTI-INLET VENTILATION SYSTEM

Abstract

Models for the jet drop distance of a free jet is presented for a side-wall multi-inlet ventilation system withadjustable flaps. The models are expressed in terms of the jet drop factor, which is a function of the inlet Archimedesnumber, the equivalent hydraulic diameter of the inlet opening and the inlet height above the floor. Jet drop models basedon the room corrected Archimedes number are established for comparison. Measurements of non-isothermal jets wereconducted in order to validate the models. Three identical pre-manufactured inlets with bottom hinged flaps and guidingplates were used in the experiments. The experiments were carried out in a full-scale room with floor dimensions of 5 m 11 m. The inlets were placed symmetrically in the inlet wall at a horizontal distance of 1.25 m between centers. The heightfrom the floor to the top of the inlet frames was 1.9 m. The jet drop distances were determined for five operating pressures,three temperature differences, three inlet opening heights and two guiding plate angles above horizontal. The method formodeling the jet drop distance, as developed by Zhang et al. (1996) for a single wall inlet, is shown to be applicable to amulti-inlet system with three inlets. Using the room corrected Archimedes number instead of the jet drop factor gave similarresults. In a ventilation control system, the jet drop distance may be used as a criterion for control of the inlets. The desiredjet drop distance may be controlled indirectly by regulating the operating pressure and the inlet opening.