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)
Characterization of the confined ceiling jet in the presence of an upper layer in transient and steady-state conditions
Although both confined and unconfined smooth ceiling jets have been previously studied, the data from small-scale experiments evaluated in this report provided a unique opportunity to characterize the transience of a ceiling jet in the presence of a developing upper layer. The development of an upper layer in an enclosure fire has notable effects on the ceiling jet. The presence of this hot gas layer increases the temperature in the ceiling jet and the heat transfer to the ceiling. Accurate prediction of the characteristics of the confined ceiling jet is important in calculating the response time of detection and suppression devices. This report examines data from a study of small-scale fire induced ceiling jet in a confined situation for a smooth horizontal ceiling. These results were obtained from experiments conducted at the National Institute of Standards and Technology, Center for Fire Research using 2.0 and 0.75 kW fires at r/H locations of 0.26 and 0.75. The data gathered from these experiments represents a collection of transient and steady-state temperature and velocity measurements of a confined ceiling jet and upper layer. The results from this data were compared to similar experimental data collected in a previous study for unconfined ceiling jet using the same apparatus. Comparison of the confined and unconfined ceiling jet data, quantification of the developing upper layer and analysis of heat transfer to the ceiling, are presented in this report. Despite the limited data, it is concluded that the unconfined ceiling jet correlations may only be valid at the very early time, prior to development of the upper layer and that steady-state unconfined correlations are certainly invalid for confined conditions. The velocity of the confined ceiling jet within the upper layer is 20-25 % less than the unconfined case affecting the heat transfer coefficient. The heat transfer analysis showed that values of 4-5 W/m2"C can be expected. Comparisons with LAVENT computer program are also presented in this report.
Estimating room temperatures from fires along walls and in corners
Determination of temperatures associated with room fires provides a means of assessing an important aspect of fire hazard: the likelihood of the occurrence of flashover. Layer temperatures in excess of 600°C have been associated with the occurrence of flashover. A data correlation has previously been presented to estimate layer temperatures for fires burning in the center of rooms. For fires in corners and along walls, restricted entrainment results in higher layer temperatures than predicted by the previous correlation. Modification factors for the previous correlation are developed to extend its applicability to wall and corner burning geometries. The present analysis suggests that a fire in a corner may cause flashover with only half the heat release rate necessary for a fire burning in the center of a room.