Algorithm for Smoke Modeling in Large,Multi-Compartmented Buildings—Implementation of the Hybrid Model

摘要

Recently, an ASHRAE research project (RP-1328) was completed in which an algorithm for a hybrid model was developed (Kashef and Hadjisophocleous 2010). The hybrid model comprised two integrated models: a zone and a networkmodel: The two-zone model was developed to simulate fire and smoke movement inside the room of fire origin and neighboring rooms. The networkmodel capable of predicting both mass and energy flow is used to simulate smoke movement into the rest of the rooms that are far away from the fire-origin room. The two models were combined to produce a hybrid model that allows an accurate simulation of fire dynamics in both the near and far field. The output of the zone model provided a direct input into the networkmodel that included the energy equation. The different steps involved in the development of the hybrid model were included in Kashef and Hadjisophocleous (2011). The application of this model permits a reasonable numerical simulation (time and accuracy) of the fire process, which determines both mass flow and energy transfer over an entire high-rise building using a standard personal computer. This paper presents the implementation of a hybrid model to simulate fires in different building geometries. The hybrid model combined two independent models: a zone model and a networkmodel. The solution procedure consisted of two parts: simulation of two-zone model, which dealt with the room of fire-origin and neighboring rooms, and simulation of the network model, which included rooms far away from the fire. The two-zone and network models were first tested individually; then the performance of the integrated model was investigated in different types of applications. The two-zone model was used to simulate afire in a room of a simple two-story, four-room building. A comparison was made between the two-zone model and CFAST (Jones et al. 2005), a well-known two-zone model for fire simulation. The network model is appropriate for rooms that are far away from the fire origin. A number of tests were performed using examples with different building geometries. A three-story, twelve-room building was used to simulate temperature and pressure changes inside compartment rooms. The mass flow rate comparison was made between the network model and CONTAM (Walton 1997), an existing network model for mass flow rate simulation. A comparison between adaptive time steps and fixed time steps was also included, showing better efficiency made by adaptive time steps. Finally, the models were integrated, where the solutions (temperature and mass flow rate) of the two-zone model become input source for the network model.