BuildSysPro.IBPSA.Airflow.Multizone.MediumColumn

# .BuildSysPro.IBPSA.Airflow.Multizone.MediumColumn

Vertical shaft with no friction and no storage of heat and mass

## Information

This model describes the pressure difference of a vertical medium column. It can be used to model the pressure difference caused by stack effect.

#### Typical use and important parameters

The model can be used with the following three configurations, which are controlled by the setting of the parameter `densitySelection`:

- `top`: Use this setting to use the density from the volume that is connected to `port_a`.
- `bottom`: Use this setting to use the density from the volume that is connected to `port_b`.
- `actual`: Use this setting to use the density based on the actual flow direction.

The settings `top` and `bottom` should be used when rooms or different floors of a building are connected since multizone airflow models assume that each floor is completely mixed. For these two seetings, this model will compute the pressure between the center of the room and an opening that is at height `h` relative to the center of the room. The setting `actual` may be used to model a chimney in which a column of air will change its density based on the flow direction.

In this model, the parameter `h` must always be positive, and the port `port_a` must be at the top of the column.

#### Dynamics

For a dynamic model, use IBPSA.Airflow.Multizone.MediumColumnDynamic instead of this model.

## Contents

Name | Description
--- | ---
Medium | Medium in the component

## Revisions

- January 18, 2019, by Jianjun Hu:
  Limited the media choice to moist air only. See #1050.
- May 1, 2018, by Filip Jorissen:
  Removed declaration of `allowFlowReversal` and changed default density computation such that it assumes a constant pressure. See #877.
- November 3, 2016, by Michael Wetter:
  Removed start values for mass flow rate and pressure difference to simplify the parameter window.
  This is for #552.
- January 22, 2016, by Michael Wetter:
  Corrected type declaration of pressure difference. This is for #404.
- February 24, 2015 by Michael Wetter:
  Changed model to use IBPSA.Utilities.Psychrometrics.Functions.density_pTX for the density computation as IBPSA.Media.Air.density does not depend on temperature.
- December 22, 2014 by Michael Wetter:
  Removed `Modelica.Fluid.System` to address issue #311.
- October 4, 2014 by Michael Wetter:
  Removed assignment of `port_?.p.nominal` to avoid a warning in OpenModelica because alias sets have different nominal values.
- April 17, 2013 by Michael Wetter:
  Reformulated the assert statement that checks for the correct value of `densitySelection`.
- July 28, 2010 by Michael Wetter:
  Changed sign for pressure difference.
- July 20, 2010 by Michael Wetter:
  Migrated model to Modelica 3.1 and integrated it into the Buildings library. Reimplemented assignment of density based on flow direction or based on outflowing state.
- February 24, 2005 by Michael Wetter:
  Released first version.

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