Location

Rolla, MO

Session Start Date

6-11-1999

Session End Date

6-17-1999

Keywords and Phrases

Area Ratio; Flow Ratio; Entrainment; Momentum; Energy; Pressure; Jet Mixing Length; Mixing Velocity; Performance; Losses; Efficiency

Abstract

Jet fans or ductless fans have been analyzed using momentum and energy considerations. This analysis is necessary for the mechanisms of mixing between the jet primary flow and the secondary or induced stream to be understood. In each case it is possible to predict performance in terms of pressure, flow ratios and hence the percentage mechanical efficiency of the whole system using equations derived from momentum and energy principles. The analysis given is suitable for situations where jet fans are utilized as area boosters in a mine ventilation system and in longitudinal vehicular tunnel ventilation. The energy and momentum equations serve as important tools for the analysis and consider all losses in the system. The derivations identified a range of flow ratios of the induced flow to the jet flow which can be used to design effective ventilation systems incorporating jet fans. Each flow ratio (n) is associated with an optimum area ratio (µ) of the jet fan outlet to tunnel, or airway area, for maximum induction or entrainment of the secondary flow. It can be shown that there is an optimum set of conditions for jet fan performance which are explained in detail in the paper.

Department(s)

Mining and Nuclear Engineering

Appears In

U.S. Mine Ventilation Symposium

Meeting Name

8th U.S. Mine Ventilation Symposium

Publisher

University of Missouri--Rolla

Publication Date

6-11-1999

Document Version

Final Version

Document Type

Article - Conference proceedings

File Type

text

Language

English

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Jun 11th, 12:00 AM Jun 17th, 12:00 AM

Theoretical Analysis of Jet Fan Performance Using Momentum and Energy Considerations

Rolla, MO

Jet fans or ductless fans have been analyzed using momentum and energy considerations. This analysis is necessary for the mechanisms of mixing between the jet primary flow and the secondary or induced stream to be understood. In each case it is possible to predict performance in terms of pressure, flow ratios and hence the percentage mechanical efficiency of the whole system using equations derived from momentum and energy principles. The analysis given is suitable for situations where jet fans are utilized as area boosters in a mine ventilation system and in longitudinal vehicular tunnel ventilation. The energy and momentum equations serve as important tools for the analysis and consider all losses in the system. The derivations identified a range of flow ratios of the induced flow to the jet flow which can be used to design effective ventilation systems incorporating jet fans. Each flow ratio (n) is associated with an optimum area ratio (µ) of the jet fan outlet to tunnel, or airway area, for maximum induction or entrainment of the secondary flow. It can be shown that there is an optimum set of conditions for jet fan performance which are explained in detail in the paper.