honeybee_energy.ventcool.opening module

Definition of window opening for ventilative cooling.

class honeybee_energy.ventcool.opening.VentilationOpening(fraction_area_operable=0.5, fraction_height_operable=1.0, discharge_coefficient=0.45, wind_cross_vent=False, flow_coefficient_closed=0, flow_exponent_closed=0.65, two_way_threshold=0.0001)[source]

Bases: object

Definition of window opening for ventilative cooling.

Parameters

  • fraction_area_operable – A number between 0.0 and 1.0 for the fraction of the window area that is operable. (Default: 0.5, typical of sliding windows).

  • fraction_height_operable – A number between 0.0 and 1.0 for the fraction of the distance from the bottom of the window to the top that is operable. (Default: 1.0, typical of windows that slide horizontally).

  • discharge_coefficient –

    A number between 0.0 and 1.0 that will be multiplied by the area of the window in the stack (buoyancy-driven) part of the equation to account for additional friction from window geometry, insect screens, etc. (Default: 0.45, for unobstructed windows with insect screens). This value should be lowered if windows are of an awning or casement type and not allowed to fully open. Some common values for this coefficient include the following.

    • 0.0 - Completely discount stack ventilation from the calculation.

    • 0.45 - For unobstructed windows with an insect screen.

    • 0.65 - For unobstructed windows with NO insect screen.

  • wind_cross_vent – Boolean to indicate if there is an opening of roughly equal area on the opposite side of the Room such that wind-driven cross ventilation will be induced. If False, the assumption is that the operable area is primarily on one side of the Room and there is no wind-driven ventilation. (Default: False)

  • flow_coefficient_closed –

    A number in kg/s-m, at 1 Pa per meter of crack length, used to calculate the mass flow rate when the opening is closed; only used in an AirflowNetwork simulation. Some common values for this coefficient (from the DesignBuilder Cracks template) include the following:

    • 0.00001 - Tight, low-leakage closed external window

    • 0.003 - Very poor, high-leakage closed external window

    (Default: 0, indicates the VentilationOpening object will not participate in the AirflowNetwork simulation).

  • flow_exponent_closed – An optional dimensionless number between 0.5 and 1 used to calculate the mass flow rate when the opening is closed; required to run an AirflowNetwork simulation. This value represents the leak geometry impact on airflow, with 0.5 generally corresponding to turbulent orifice flow and 1 generally corresponding to laminar flow. (Default: 0.65, representative of many cases of wall and window leakage, used when the exponent cannot be measured).

  • two_way_threshold – A number in kg/m3 indicating the minimum density difference above which two-way flow may occur due to stack effect, required to run an AirflowNetwork simulation. This value is required because the air density difference between two zones (which drives two-way air flow) will tend towards division by zero errors as the air density difference approaches zero. (Default: 0.0001, typical default value used for AirflowNetwork openings).

Properties:

  • fraction_area_operable

  • fraction_height_operable

  • discharge_coefficient

  • wind_cross_vent

  • flow_coefficient_closed

  • flow_exponent_closed

  • two_way_threshold

  • parent

  • has_parent

ToString()[source]

Overwrite .NET ToString.

duplicate()[source]

Get a copy of this object.

classmethod from_dict(data)[source]

Create a VentilationOpening object from a dictionary.

Parameters

data – A VentilationOpening dictionary in following the format below.

{
"type": "VentilationOpening",
"fraction_area_operable": 0.5,  # Fractional number for area operable
"fraction_height_operable": 0.5,  # Fractional number for height operable
"discharge_coefficient": 0.45,  # Fractional number for discharge coefficient
"wind_cross_vent": True  # Wind-driven cross ventilation
"flow_coefficient_closed": 0.001 # Coefficient for mass flow rate
"flow_exponent_closed": 0.667 # Exponent for mass flow rate
"two_way_threshold": 1e-3 # Minimum density for two-way flow
}
to_dict()[source]

Ventilation Opening dictionary representation.

to_idf()[source]

IDF string representation of VentilationOpening object.

Note that this ventilation opening must be assigned to a honeybee Aperture or Door for this method to run. This parent Aperture or Door must also have a parent Room. It is also recommended that this Room have a VentilationControl object under its energy properties. Otherwise, the default control sequence will be used, which will likely result in the window never opening.

Also note that the parent’s geometry should be in meters whenever calling this method and that this method does not return full definitions of ventilation control schedules. So these schedules must also be translated into the final IDF file.

property discharge_coefficient

Get or set a number for the discharge coefficient.

property flow_coefficient_closed

Get or set a number for the mass flow coefficient when opening is closed [kg/s-m].

Note that anything assigned here has no bearing on the simulation unless the Model that this object is a part of has its ventilation_simulation_control set for MultiZone air flow, thereby triggering the use of the AirflowNetwork.

property flow_exponent_closed

Get or set the exponent for deriving the mass flow rate when opening is closed.

Note that anything assigned here has no bearing on the simulation unless the Model that this object is a part of has its ventilation_simulation_control set for MultiZone air flow, thereby triggering the use of the AirflowNetwork.

property fraction_area_operable

Get or set a number for the fraction of the window area that is operable.

property fraction_height_operable

Get or set a number for the fraction of the window height that is operable.

property has_parent

Get a boolean noting whether this VentilationOpening has a parent object.

property parent

Get the parent of this object if it exists.

property two_way_threshold

Get or set minimum density difference above which two-way flow occurs [kg/m3].

Note that anything assigned here has no bearing on the simulation unless the Model that this object is a part of has its ventilation_simulation_control set for MultiZone air flow, thereby triggering the use of the AirflowNetwork.

property wind_cross_vent

Get or set a boolean for whether there is cross ventilation from the window.

Note that this property only has significance for simulations using SingleZone ventilation_simulation_control and has no bearing on multizone simulations with the Airflow Network.

This should be True if there is an opening of roughly equal area on the opposite side of the Room such that wind-driven cross ventilation will be induced. If False, the assumption is that the operable area is primarily on one side of the Room and there is no wind-driven ventilation.