Sprinklers påverkan på ventilationsbrandskydd : En funktionsanalys avseesnde sprinklers påverkan på brandgasspridning i hotellmiljö.

Sammanfattning: The fact that a building is covered by a well-arranged fire protection is today a basic precondition for the safety of a building. Good and organized fire protection is also an essential part of a good safety culture. For this reason, it is common for buildings to be equipped with a higher fire protection than what is required by current regulations. In buildings intended for hotel services, sprinklers are usually installed even though it is not required. Fans in operation is a protection method for the ventilation that falls within the framework of analytical dimensioning, where an analysis is required to verify the formation. As the name implies, fans in the operating solution are based on the fans continuing to run in the event of a fire, the protection mechanism is that the pressure in the supply air duct must be overcome by the fire pressure before the fire gases can spread. As a calculation basis for the verification, the fire pressure (when sprinklers are not used) amounts to 1500 Pa and the fire gases temperature in the early stage of the fire to 350 ͦ C according to Boverkets “allmänna råd” (BFS 2013: 2) on analytical dimensioning of buildings fire protection (BBRAD3). When using sprinklers, these values ​​are expected to be much lower, which should also change the conditions for fire protection design. Together with the fans in operation method, self-actuating backflow protectors is often used, which completely restricts the flow in the supply air duct when the fire pressure becomes too high and the flow reverses, but these are relatively costly. The thesis mainly aims to investigate whether deviations from the fire technical installation of backflow protection can be made in buildings where sprinklers have been installed. This in the hope of finding more cost-effective solutions and at the same time achieve satisfactory fire protection. To get an answer to if the deviation can be made, the computer programs Fire Dynamics Simulator (FDS), Program Flow System (PFS) and material from an existing project have been used. As a complement, a small literature study has also been done to gain a basic understanding of the underlying theory and to substantiate proposed solutions. Various CFD (Computational Fluid Dynamics) programs are often used in many engineering professions. The basis for the programs is that they are based on flow calculations based on the Navier-Stokes equations. FDS is a CFD program adapted for simulations of fire scenarios. PFS is a ventilation program where flows can be calculated, both during normal circumstances and in the happening of fire. In FDS, a hotel room was built based on the existing project and requirements from BBRAD3. Based on data given in the FDS runs, the fire gas spread via the ventilation system was calculated using PFS. The result shows that a possible design of the ventilation technical fire protection without backflow damper is not possible to achieve a satisfactory fire protection. This is because the spread of fire gases to the adjacent fire compartment exceeded the requirement of 1% of its volume. The results show, however, that there are several different acceptable ventilation technical solutions in the form of an increased capacity of the supply air fan in the event of a fire or by installing a flow adjustment damper on the supply air duct. When applying the flow adjustment damper as a fire technical solution, the result has shown that with a 200 Pa pressure relief on the damper, the fire gas spread is less than the 1% requirement. When the pressure in the supply air ducts becomes higher, the possibility of fire gases spreading becomes more difficult. As the estimated fire gas spread was below the requirements, this solution is also considered to be applicable in buildings that are slightly more airtight than the building studied. A disadvantage, however, is that more powerful fans for the supply air will have to be used, which can increase operating costs and energy use. The other proposed fire technical solution was to increase the capacity of the supply air fan from normal operating function to 350 Pa and 380 Pa pressure effect in the event of a fire. This function is intended to be connected to the building's fire alarm. In the event of a fire, the fire alarm should be activated at an initial stage so that the supply air fan can reach the selected capacity within 44 seconds. Since at 44 seconds the normal pressure drop of 50 Pa in the supply air duct is overcome, which means that fire gas spread from the fire compartment to adjacent fire compartments is initiated. The application of an existing or external supply air fan whose capacity only increases if it is activated by a fire alarm is the report's main solution for maintaining satisfactory fire protection when substituting a backflow damper. This is because the solution is considered to be the most cost-effective.