modelExtConvForcedCoeff
Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).
Information
This model calculates the convection coefficient at an exterior surface for pure forced flow conditions for low-rise buildings. The forced flow coefficient resulting from this model is combined in IDEAS.Buildings.Components.BaseClasses.ConvectiveHeatTransfer.ExteriorConvection with a coefficient for purely natural convection conditions to produce a coefficient for combined natural and forced flow.
It applies the "MoWitt" correlation for forced flow, which is empirically derived from a Window test facility. The correlation's coefficients are taken from the EnergyPlus v8.9 Engineering manual (Table 3.9, Page 95). Different coefficients are used in the correlation depending on whether the surface is "windward" or "leeward". In this implementation a vertical surface is considered leeward if the wind angle is more than 100 degrees from normal incidence. Ceilings are always treated as windward, while floors are always treated as leeward.
Horizontal surfaces are treated as either a ceiling or a floor. Any non-horizontal surface is treated as vertical.
The wind speed from the weather file is used in the MoWiTT correlation: no adjustments are made for building height or local wind sheltering. The MoWiTT correlation assumes that the wind speed is measured at the weather station.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Units.SI.Angle | inc | Surface inclination | |
| Modelica.Units.SI.Angle | azi | Surface azimuth |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Blocks.Interfaces.RealOutput | hForcedConExt | Forced flow convective heat transfer coefficient at exterior surface | |
| Modelica.Blocks.Interfaces.RealInput | winSpe | Wind speed | |
| Modelica.Blocks.Interfaces.RealInput | winDir | Wind direction |
Revisions
-
November 28, 2019, by Ian Beausoleil-Morrison:
First implementation. See #1089