Details on “Calculation Presettings” in the "Settings” (Ventilation)
Information about the Calculation Presettings section of the Settings dialog in the Pipe and Air Duct Network Calculation Ventilation.
In this section, you can make global settings for the calculation. The settings are saved in the project.
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Density
Height Above Sea Level, Atmospheric Pressure
Enter the height above sea level for the project. The corresponding atmospheric pressure is determined using the barometric altitude formula and used to convert the volume flow rates in heaters and coolers.
Dimensioning Presettings
Maximum velocity and maximum pipe friction pressure loss are used for dimensioning ducts and pipes. Use the checkboxes to specify which settings are to be taken into account. You can include both specifications.
Maximum Velocity
Enabled: The maximum velocities are taken into account as dimensioning presettings. Specify whether the velocity limits are defined according to Topology or Volume Flow Rates.
by topology
Enabled: The velocity limits according to the topology of the network are used as dimensioning presettings. To this end, the maximum permissible velocities for the Connecting Pipes and for the Distribution/Collection Pipes are specified.
Connection Pipes, Distribution/Collection Pipes
Specify the maximum permissible velocities for the respective pipe types. For free dimensioning, the dimensions must be at least large enough to comply with the limits. For fixed dimensions, a warning is issued for the relevant sections if the velocity limits are exceeded.
according to Volume Flow Rates
Enabled: The velocity limits of the individual volume flow rate intervals are used as dimensioning presettings.
The button According to Volume Flow Rates opens the Velocity Limits dialog, in which the volume flow rate intervals are defined. The dialog already contains appropriate values, which you can adjust if necessary. You can only define the flow rate limits of the intervals by using the upper limits. If you change the upper limit of an interval, the lower limit of the following interval is automatically adjusted. Use the tilde symbol (~) to set an open upper limit for the volume flow rate, which is required for the upper limit of the last volume flow rate interval.
Max. Pipe Friction Pressure Loss
Enabled: The specified maximum pipe friction loss (dp-max) is used as a dimensioning presetting. With free dimensioning, dimensions are set so that this limit is adhered to. If the duct dimensions are fixed, a warning is issued for the corresponding sections if this value is exceeded.
Volume Flow Rate Unit
Drop-down list to select the unit of the Volume Flow Rate. The unit is used in all dialogs and printouts.
Medium Table ...
The button Medium Table ... opens the dialog Medium, in which you can load media from MDD files, adjust the material values of the media, and create your own media.
Outdoor Air
The air condition of the outdoor air is defined by the Average Temperature and the Average Humidity. This information serves as a guideline for the values in the weather protection grilles or roof hoods, which are the starting values for the network. By cross checking with the requirements for rooms, heating- or cooling-capacity or in- or output values for (de-) humidifiers can be preset.
Zeta Values
Use the drop-down list to specify the data source for determining the zeta value, e.g., according to the HVAC Manual.
Extrapolate Table Values
Enabled: To determine the Zeta values, the values from the tables of the selected data source are extrapolated.
Zeta value if not automatically calculable
If the dimensions and volume flow rates of a component are outside the limits of the data sources for determining the zeta value, no zeta value can be determined. In such cases, the specifications set out here shall be used. You have two options for the settings:
for All Components: The zeta value entered here is used for all components for which no zeta value can be determined.
by Component Types…: If no zeta value can be determined for a component, it is assigned a value according to its component type. The assignment of the corresponding zeta values to the component types is made via the Default Zeta Values by Component Type dialog, which you open via the buttonby Component Type ....
Additional calculation specifications (checkboxes)
| Check box | Description |
|---|---|
| Consider mixing temperature | Enabled: Volume flow rates are determined and cumulated under consideration of the temperature. In case of a temperature change, the volume flow rates are adjusted according to the changed density. A temperature change can be achieved by conditioning (heater, cooler) or by mixing volume flows of different temperatures. Disabled: All volume flows are determined and cumulated without consideration of temperature and density changes. At the fan, the volume flow is thus the sum of the entered volume flows of the air diffusers. If you deactivate this option, a message appears asking you to deactivate the functionality and whether this is desired. |
| Balancing regulating device | Enabled: After calculation, the control elements are adjusted so that the flow paths have the same total pressure loss as the most unfavorable flow path. Disabled: The control elements are not adjusted after the calculation, and the results are the values of the unregulated network. |
| Perform sound level calculation | Enabled: During calculation, acoustics are also calculated according to VDI 2081. |
| Recalculate after editing of pipe sections or components | Enabled: After each edit of sections or components in the calculation dialog, the calculation is automatically performed again. Disabled: The calculation results are only updated after clicking on Calculate in the calculation dialog. |
| Material detection during every calculation | Enabled: The material is recalculated for each calculation. Material detection is necessary, for example, for creating parts lists and assigning component connections. Disabled: The material is not detected during calculation. For large project where changes in material are not to be expected, this can shorten calculation time. If the checkbox is unchecked and you want to create printouts using the Output... function, you will be asked whether the material should be detected. |
| Output Manufacturer-neutral Material | Enabled: When issuing parts lists, manufacturer components are listed without the manufacturer name and without the item number in the neutral components section. If you change this option, you must recalculate the network before reissuing it. |