- Author
- Mercier, G. P. | Jaluria, Y.
- Title
- Fire-Induced Flow of Smoke and Hot Gases in Open Vertical Shafts.
- Coporate
- Rutgers Univ., New Brunswick, NJ
- Sponsor
- National Institute of Standards and Technology, Gaithersburg, MD
- Contract
- NIST-GRANT-60NANB1H1171
- Book or Conf
- Thermal Science and Engineering Symposium in Honor of Chancellor Chang-Lin Tien. Proceedings. November 1995, Berkeley, CA, 261-268 p., 1995
- Keywords
- smoke | high temperature gases | heat transfer | building fires | temperature field | flow rate | ventilation
- Identifiers
- schlieren photographs of the buoyant flow near the inlet of the vertical shaft with inlet velocity increasing from left to right; effect of injected mass flow rate and inlet temperature difference from the ambient on time taken by injected smoke to reach the top opening; measured vertical velocity variation across the shaft at different vertical locations and different values; measured vertical velocity variation across the shaft at different vertical locations and different values of Re; sketch of the flow pattern observed in the vertical shaft for the conditions considered here
- Abstract
- An experimental study on the flow and heat transfer in vertical shafts due to a building fire is carried out. Smoke or hot gases are injected into the shaft at a lower opening and the downstream flow and temperature fields are studied. The inlet temperature and flow rate of the hot gases are varied over wide ranges to simulate the flow due to fire in multi-leveled buildings with vertical open shafts under natural ventilation. The conditions at the outlet are also monitored to determine the effects of entrainment into the flow and heat transfer to the walls. Typical values of the operating conditions have been investigated, ranging from high buoyancy levels, for which the flow stays close to the vertical wall of the shaft, to much lower levels, at which the flow enters the shaft with a significant flow velocity and spreads outward very quickly. It is found that with increasing temperature at the inlet, the buoyancy effect is larger resulting in higher velocities and shorter time to reach the top. The temperature at the outlet depends on heat transfer to the walls as well as on the flow velocity and is measured. Detailed measurements of the velocity and temperature fields have also been taken. It is found that a wall plume is generated which conveys the hot fluid rapidly along the shaft wall from the inlet to the outlet. A recirculating flow arises away from this wall and this flow affects the heat transfer and flow in the wall plume. This, in turn, affects the entrainment into the flow, decay of the temperature field and rate of downstream movement. Therefore, horizontally uniform conditions can not be assumed here, as employed in several studies for tall shafts. The wall plume has to be modeled in this case, considering the entrainment into the boundary layer flow and the effect of the recirculating flow.