It uses the local pressure (which includes the zone pressure), which allows for leakage to vary in magnitude.” ( McGrattan et al. … The second approach is intended for leaks with well defined locations (a cracked open door where the crack size is subgrid) or for leaks where the stack effect is important. In this approach surfaces within a pressure zone are denoted as leaking and those surfaces can be considered an HVAC vent that connects to the outside via a tiny duct whose area is the leakage area.
The first approach is by exploiting only pressure zones.Ī pressure zone is a user-specified volume within the computational domain that is entirely surrounded by solid obstructions.įor example, the interior of a closed room can be, and should be, declared a pressure zone. This allows the leakage to be removed over a large area in the domain (just as it would be in reality) while correctly capturing the actual area of the leakage path. “The compartment surface that is leaking can be thought of as a large HVAC vent that connects via a very small duct to the outside. Pressure zones and leaks are discussed in Section 9.3 of the FDS User’s Guide. The leakage area can be smaller than the mesh size so the gaps cannot be modeled directly, instead the HVAC model in FDS is used to connect the leaking compartment to the outside. Leakage refers to the air that escapes through small gaps (i.e at the top of a door) as a compartment is pressurized by a fire. Since version 2017.2, PyroSim has supported both pressure zone and local HVAC leakage in the user interface. This post gives examples of leakage modelling using pressure zones and HVAC vents. To follow along with this tutorial, download the relevant files here.
Created with software version: 2020.1 Table of Contents