Verifiering av ventilationsbrandskydd : Med hjälp av FDS 6 HVAC- funktion

It is difficult to predict if there is a risk for fire smoke spread through a ventilation systems and it is often required analytical design for verifying adequate fire protection. Different simulation programs are used today to verify the protection against fire of the ventilation system. FDS is a simulation program which by edition six came with an additional function, HVAC (Heating, Ventilation, and Air Conditioning) where natural- and mechanical ventilation may be simulated using a system built by nodes and ducts. The function also allows leakage to be simulated in a computationally more stable way than before. The HVAC function is indirectly coupled to the CFD calculations in FDS to avoid dividing the system in grid cells which would have required far more computing capacity. HVAC has been validated against full-scale test with satisfactory results.This study aims to investigate how the HVAC function can be used in analytical design and investigate its limitations and user friendliness. Four parameter studies was performed using FDS and HVAC where the fire compartment size-, the wind-, the material selection and the leak impact on inter alia pressure, temperature and amount fire smoke spread was investigated. The model was built in form of an apartment building with two apartment floors and one attic with belonging FT-system with fans in operation. The result showed that the main risk for fire smoke spread through the ventilation system appeared in the early course of the fire development where the increase of the temperature was greatest. The possibility of decompression in the fire compartment was also a factor which had high impact on the fire smoke spread through the ventilation system where an increase in pressure relief reduced the spread. A volume reduction of the fire compartment decreased the amount distributed fire smoke in the initial stage and the wind factor reduced the spread but increased the fire effect after the windows broke. The heat resistance of the windows was also of significance when looking at the amount of fire smoke spread through the ventilation system, why the temperature for window failure is something that should be investigated further. The suitability of using the HVAC function to verify ventilation systems against fire is considered to be good. However, the programs application area for the different functions requires good knowledge to achieve satisfactory results. It is noticeable that the function is new since certain variables, such as the duct temperature and the self-designed fan curve, are not yet fully developed in function and construction. Construction of advanced ventilation systems and other types of buildings should also be implemented in the program and validated against full-scale experiments.Validerat; 20140624 (global_studentproject_submitter