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Reply to comments of Thomas and Bullen
COMBUSTION AND FLAME
37:105 (1980)
105
Reply to Comments of Thomas and Bullen V. BABRAUSKAS Centerfor Fire Research, National Bureau of Standards, Washington, D.C.
and U. G. WICKSTROM Division of Structural Mechanics and Concrete Construction, Lund Institute of Technology, Lund, Sweden
Our response to the comments of Thomas and Bullen [1] is as follows: 1. Wall losses are properly treated in the model. Convenient graphs of results are, however, not possible for general transient wall heating. At short times, the walls are effectively more lossy. No additional regimes of combustion resuit; the Takeda-Nakaya lower limit is due to gas-phase kinetics. 2. The variable r/ is valid for describing combustion at both A and B. We do not see, however, a serious utility for detailed study of the unsteady equilibrium case. 3. Point C does exist physically. It is simply the nearly free burning of a fuel in the room, where the room's existence changes the burning little from that out in the open air. Even though
Copyright © 1980 by the Combustion Institute Published by Elsevier North Holland, Inc.
numerically it can be accommodated into our model (or Thomas's), it is not logical to do so. These models assume that the hot gases are stirred and uniform in temperature. The nearly free burning, on the other hand, occurs only with very small fires or in the early stages of larger fires, where the hot gas distribution is characterized by sharp and significant gradients.
REFERENCE 1. Thomas, P. H., and Bullen, M. L., preceding communication. Received 9 May 1979
0010-2180/80/010105+1501.75
37:105 (1980)
105
Reply to Comments of Thomas and Bullen V. BABRAUSKAS Centerfor Fire Research, National Bureau of Standards, Washington, D.C.
and U. G. WICKSTROM Division of Structural Mechanics and Concrete Construction, Lund Institute of Technology, Lund, Sweden
Our response to the comments of Thomas and Bullen [1] is as follows: 1. Wall losses are properly treated in the model. Convenient graphs of results are, however, not possible for general transient wall heating. At short times, the walls are effectively more lossy. No additional regimes of combustion resuit; the Takeda-Nakaya lower limit is due to gas-phase kinetics. 2. The variable r/ is valid for describing combustion at both A and B. We do not see, however, a serious utility for detailed study of the unsteady equilibrium case. 3. Point C does exist physically. It is simply the nearly free burning of a fuel in the room, where the room's existence changes the burning little from that out in the open air. Even though
Copyright © 1980 by the Combustion Institute Published by Elsevier North Holland, Inc.
numerically it can be accommodated into our model (or Thomas's), it is not logical to do so. These models assume that the hot gases are stirred and uniform in temperature. The nearly free burning, on the other hand, occurs only with very small fires or in the early stages of larger fires, where the hot gas distribution is characterized by sharp and significant gradients.
REFERENCE 1. Thomas, P. H., and Bullen, M. L., preceding communication. Received 9 May 1979
0010-2180/80/010105+1501.75