Computational and Experimental Study of Smoke Flow in the Stair Shaft of a 10-Story Tower
CONTAMW is an indoor air quality analysis network model developed to determine airflow and contaminant concentrations in each compartment of a building. In addition to its applicability in indoor environment modeling, CONTAMW is also used to model smoke control systems in multi-story buildings. This study investigates whether this model can accurately predict smoke movement in a multi-story building by comparing its predictions with data from experiments conducted in the 10-story test facility of the National Research Council of Canada (NRC). The 10-story experimental facility at NRC was designed to simulate the center core of a high-rise building, including corridors and stair and elevator shafts. Various vents on the external and internal walls can be opened or closed to simulate the leakage area of typical buildings. Comparisons with two sets of experimental data are presented in this paper. In the first experiment, a propane burner was used to produce a constant heat release rate of 1 MW. In the second experiment, a couch was used as the fuel with the average heat release rate being 730 kW. The measured CO2 concentrations and pressure in the stair shaft are compared with the results predicted using the model. The results indicate that the model underpredicts the CO2 concentrations. A large difference between predicted and measured pressure also exists. In addition, the two-zone model FIERAsmoke is used to predict CO2 concentrations in the stair shaft. The two-zone model predictions compare better with the experimental data than the predictions of the network model. INTRODUCTION The stair shafts in a multi-story building are one of the means of smoke spread between floors, and there are many fire incidents where building occupants have died in stair shafts or corridors of floors above the fire floor due to smoke inhalation while attempting to evacuate (Proulx 1996). There are mainly three modeling approaches that can be used for this problem (Hadjisophocleous and Fu 1999; Milke and Mowrer 1994): network models, zone models, and CFD models. CONTAMW is a network model that treats each compartment in a building as a single zone (Dols et al. 2000). It is mainly used to model indoor air quality by calculating airflow and contaminant concentrations. Its ability to calculate building airflow is useful to assess the adequacy of ventilation rates, the variation in ventilation rates, and the distribution of ventilation air. The prediction of contaminant concentrations can be used to determine the indoor air quality performance of a building and investigate the impacts of various design decisions. This model has a very good user interface in which all the components of the building, such as walls, compartments, and vents, can be schematically drawn using drawing tools and libraries of icons. Various parameters associated with each component can be conveniently entered through the interface. It also allows a user to view the simulation results on the screen or output them to a file for further analysis. The model does not consider heat transfer and energy balance, and thus the temperature of each zone cannot be predicted but has to be input as a constant value. Due to its ability to predict contaminant flow in a building, the model is used to simulate smoke movement in high-rise buildings and to assist in the design of smoke management systems. 724 ASHRAE Transactions: Symposia George Hadjisophocleous is a professor and Zhuman Fu is a post-doctoral fellow in the Department of Civil and Environmental Engineering, Carleton University, Ottawa, Ontario, Canada. Gary Lougheed is a senior research officer in the Fire Risk Management Program, Institute for Research in Construction, National Research Council Canada, Ottawa. This study uses CONTAMW to simulate experiments performed in the 10-story experimental tower facility of NRC. This facility was designed to simulate the center core of a highrise building, including corridors and stair and elevator shafts. Various vents on the external and internal walls can be opened or closed to simulate the leakage area of typical buildings. Two experiments were compared with the model predictions. One experiment used propane as fuel, another one used a couch as fuel. CO2 concentrations and pressure in the stair shaft are the two parameters compared with the model predictions. This paper also includes comparisons of predictions obtained from a two-zone smoke movement model FIERAsmoke (Fu and Hadjisophocleous 2000). In the following, the experimental facility is described and then the two-zone model FIERAsmoke. Finally, the experimental results and the predictions of CONTAMW and FIERAsmoke are compared and analyzed. DESCRIPTION OF THE FACILITY Experiments were conducted in a 10-story experimental facility at NRC. This facility was designed to simulate a highrise building, including corridors and stair and elevator shafts. Various vents on the external and internal walls can be opened or closed to simulate the leakage area of typical buildings. Figure 1 shows the floor plan of the facility. As shown in Figure 1, the floor is divided into two parts: service area and test area. The doors between the test and service areas were closed during the tests, so the service area is not considered in the calculations. In the test area, there are a number of compartments on each floor. The main compartment, the east and west corridors, the stair shaft lobby, and stair shaft are connected through various vents. None of the other compartments within the test area, such as the elevator shafts as shown in Figure 1, were connected to the smoke flow path during these tests. Thus, these compartments were not considered in the calculations. In addition, to simplify the problem, in the model the stair hall is combined with the west corridor due to its small size. With these simplifications, four compartments were modeled on each floor: main compartment, east corridor, west corridor, and stair shaft. The dimensions of each compartment are given in Table 1. The main compartments are connected directly to the east corridors. Between the east and west corridors of each floor, there is an open standard door. Both east and west corridors have a small wall vent connected to the outside representing wall leakage. There is a small vent between the west corridor and the stair shaft also representing a specified leakage area. In addition, there is a standard door between the stair hall and stair shaft on the fire floor, which is open during the tests. The dimensions of all the openings, including doors and vents, are given in Table 2. In the tests, the fire was located in the main compartment on the second floor. Concentrations of carbon dioxide in the stair shaft on the second, sixth, eighth, and tenth floors were measured. Temperature in the stair shaft was also measured. Only one point measurement was made for the CO2 concentration and temperature of each floor. The measuring point was at the mid-height between the two floors. In this study, the measured CO2 concentrations and temperatures are assumed to represent the smoke layer values on that floor. These data will be compared with the model predictions. DESCRIPTION OF THE TWO-ZONE MODEL A two-zone smoke movement model was developed and coded using Visual Basic. Details of the model are provided in Fu and Hadjisophocleous (2000). This paper gives a brief description of the conservation equations of the model and the fire submodels, as well as a detailed description of the stair shaft flow model. Figure 1 Floor plan of the 10-story smoke tower. TABLE 1 Dimensions of the Compartments of the 10-Story Tower Length (m) Width (m) Height (m) Main compartment 8.9 3.71 2.4/3.3 East corridor 13.65 1.17 2.4/3.3 West corridor 16.05 1.17 2.4/3.3 Stair shaft 5.0 2.46 2.4/3.3 The ceiling height is 3.3 m for floors 1 and 2, and 2.4 m for others. TABLE 2 Dimensions of the Vertical-Vents of the Building Sill Height (m) Soffit Height (m) Width (m)
Calculating combined buoyancy- and pressure-driven flow through a shallow, horizontal, circular vent: Application to a problem of steady burning in a ceiling-vented enclosure
A model was developed previously for calculating combined buoyancy- and pressure-driven (i.e. forced) flow through a shallow, circular, horizontal vent where the vent-connected spaces are filled with fluids of different density in an unstable configuration (density of the top fluid is larger than that of the bottom). In this paper the model is summarized and then applied to the problem of steady burning in a ceiling-vented enclosure where normal atmospheric conditions characterize the upper-space environment. Such fire scenarios are seen to involve a zero to relatively moderate cross-vent pressure difference and bidirectional exchange flow between the enclosure and the upper space. A solution to the problem leads to a general result that relates the rate of energy release of the fire to the area of the vent and the temperature and oxygen concentration of the upper portion of the enclosure environment. This result is seen to be consistent with previously published data from experiments involving ceiling-vented fire scenarios.
HYPERGOLIC REACTION MECHANISMS OF CATALYTICALLY PROMOTED FUELS WITH ROCKET GRADE HYDROGEN PEROXIDE
Abstract The coupling of the physical and chemical processes controlling the ignition delays (τ ign ) of hypergolic propellants complicates the direct analysis of the transient ignition processes. The transport properties of both the propellants and the ambient gas, and the heat of vaporization and reaction affect τ ign and must be considered experimentally. Furthermore, since hypergolic ignition occurs, by definition, on contact, the mechanics of initial contact and subsequent mixing can affect τ ign and must also be considered. Experimental results from a study of the hypergolic ignition of a catalytically promoted fuel with rocket grade hydrogen peroxide (RGHP) are presented. Statistical analysis of the experimental data was conducted to evaluate the relative effects of RGHP concentration, initial ambient pressure, and the ambient gas on τ ign . At RGHP concentrations of less than 92% in water, stable ignition was difficult to achieve. At sufficiently high Lewis number, an oscillatory ignition process is observed. A phenomenological model comprising mixing, RGHP decomposition, fuel heating and vaporization, and auto-ignition is presented and compared to the experimental results.