Experimental investigation of a ventilation system based on wall confluent jets

• Published in: Building and environment 2014-10, Vol.80, p.18-31
• Main Authors: Janbakhsh, S., Moshfegh, B.
• Format: Article
• Language: English
• Subjects: Air; airflow; Applied sciences; Building insulation; Building technical equipments; Buildings; Buildings. Public works; Construction; Decay rate; Draught rate; Draughts; Environmental engineering; Exact sciences and technology; Experimental investigations; experimental study; External envelopes; Floors; Inlet flow; Inlets; Isotherms; jet flow; Jets; Measurement; measurement method; Measurements; Minimum temperature differences; Spreading; Supply device; temperature profile; Temperature profiles; Thermal comfort; Thermal comfort index; Thermal comfort indices; turbulence; Turbulence intensity; Velocity; Velocity and temperature fields; velocity profile; Ventilation; Ventilation system; Ventilation systems; Ventilation. Air conditioning; Wall confluent jets; Walls
• ISSN: 0360-1323; 1873-684X; 1873-684X
• DOI: 10.1016/j.buildenv.2014.05.011

The flow behavior of isothermal and non-isothermal wall confluent jets (WCJ) ventilation system was investigated experimentally in a mock-up office environment. Two flow regions were identified: first, a primary region is developed below the supply device, with axis along the inlet wall, and a secondary wall-jet forms along the floor. The velocity and temperature fields were recorded by traversing a hot wire and thermistor anemometers for both primary and secondary regions. The results show self-similarity characteristic of the velocity and temperature profiles for both isothermal and non-isothermal WCJ. Maximum velocity decay and its spreading rate are linear and independent of the inlet airflow rate. Minimum temperature difference and its spread also show linear decay. The spreading rates for maximum velocity are similar in both the primary and secondary regions normal to the inlet wall and floor, respectively, which is consistent with previous studies on wall jets. The variation of draught rating is evaluated via mean velocity, turbulence intensity and temperature. Although the WCJ has slow velocity decay, which enables it to cover almost the entire floor of the test room, the draught is acceptable in the occupied zone according to ISO 7730. PMV (predicted mean vote) and PPD (predicted percentage dissatisfied) are presented for the occupied zone of the room. •The flow field of the WCJ confirms the primary and secondary jet regions in the studied room.•Self-similarity characteristic of the velocity and temperature profiles can be observed.•Correlation for maximum velocity decay and normal spreading rate are presented.•Correlation for decay of minimum temperature difference has been provided.•Draught rate, PMV and PPD have been evaluated in the occupied zone.