JET-FAN VENTILATION

Tunnel ventilating systems are discussed and a jet fan system designed to maintain pollutants below the design level is described. An automatic fan control system has been devised to switch off half of the fans when pollutant concentrations are low and ensure that the fresh air flow is in the direction of the prevailing wind. The theory on which the jet-fan model is based is detailed. The fan thrust, tunnel resistance, vehicle drag and external wind force are all determined by means of equations. The jet fans for the Terrace Tunnel are fully reversible. If the direction of the piston effect is the same as the direction of the net external wind force, the fans may be run in the direction to take advantage of this external assistance. The direction in which the fans are switched on is controlled by a wind vane suspended from the tunnel ceiling. The purpose of the wind vane is to detect the direction of tunnel are flow due to the net effect of external winds and traffic piston-effect. The data upon which the system is based on an average specific emission rate of approximately 40 g CO/km. If the 1980 goal of 2.1 g CO/km is attained, the Terrace Tunnel may require ventilation only for emergencies.

  • Availability:
  • Corporate Authors:

    Technical Publications Limited

    C.P.O. 3047
    Wellington,   New Zealand 
  • Authors:
    • Ostling, A R
  • Publication Date: 1975-8-15

Media Info

  • Features: Figures; References; Tables;
  • Pagination: p. 231-235
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00128557
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Mar 10 1981 12:00AM