Infiltration

In ESP-r air movement from the outside into zone is termed infiltration

and can be scheduled or represented by components and connections in a flow network. Scheduled infiltration can be modified to account for wind speed is the user has a strong opinion. It can also be controlled by the room temperature or outside ambient temperature and thus roughly approximate natural ventilation. Such user imposed regimes are not physically based but suffice for Engineering checks.

In many cases a better alternative is to represent Infiltration by describing the leakage paths in the facade as well as windows and their opening regimes within a flow network.

Resolving pressures at facades

In ESP-r one of the databases is a pressure coefficients database which holds pressure relationships at 22.5 degree increments. These are used to resolve pressures at facades from wind directions and velocities in the weather file. Each boundary nodes in a flow network is associated with one of the coefficient sets. They might be based on physical tests or virtual tests.

Infiltration leakage paths

Examples of faults in facades or architectural details that provide leakage paths are:

  • cracks around windows and doors - crack components with length and width parameters are often used. They could be aggregated for each facade in each room or each crack could be separately defined. Such cracks can also be associated with boundary cells in a CFD domain to allow wind-driven flow to be included.
  • Grills in facades could be represented as common orifices with a suitable discharge coefficient or as part of a conduit where the hydraulic diameter of the duct and a local loss factor can be included.

    • Use of blower door tests

    In ESP-r fixed pressure nodes can be used to represent a blower door test. For example rather than a wind driven boundary node a fixed 50Pa could be set and the zone node fixed at zero Pa. Cracks of different lengths and widths could be tested to find a combination that resulted in the overall flow of a physical blower door test.

    Use of stack pressures in resolving infiltration

    The vertical location of flow nodes and flow components are required and this allows for stack to be calculated as part of the network flow solution. Stack pressures are separately reported.

    Indoor air quality

    IAQ assessments can be carried out within the context of a flow network. Additional information is needed to define contaminate sources and bookkeepping as part of the mass flows is post-processed into contaminate distributions.


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    ©Copyright 2017 Energy Systems Research Unit, Glasgow, Scotland. License: GPL V2. Last edited by JWH, 20 Aug 2016