Regular Article

Analysis of room overpressure after launching an integrated extinguishing system

¹ University of West Bohemia in Pilsen, New Technologies − Research Centre, Univerzitní 2732/8, 301 00 Pilsen, Czech Republic
² Safran Cabin CZ s.r.o., Univerzitní 1119/34, 301 00 Pilsen, Czech Republic

^* e-mail: hurda@ntc.zcu.cz

Received: 31 March 2019
Accepted: 3 November 2019

Abstract

The throttling of liquefied substances from high pressure vessels to an enclosed volume starting at atmospheric pressure is described in order to determine the thermodynamic state of gaseous contents of the extinguished room. A time dependent, 0D mathematical model is implemented describing the state inside the agent container, the isenthalpic throttling in the distribution system, agent vaporization and mixing with air. The agent is modelled as real gas, and solid–vapour two phase behaviour is approximated. Other influences on the process including the heat transfer from selected solid parts inside the room and the gas mixture leakage out of the room are taken into account. The main outcome is an MS Excel tool for the design optimization of integrated fire extinguishers. The optimization balances two contradictory requirements: volumetric concentration of the agent to sustain the fire extinguishing capabilities, and tolerable room overpressure. Agent fill weight and discharge time are adjusted. The discharge time is controlled by the distribution piping and design of the spray nozzles. System operation is checked with regards to various initial and boundary conditions.