BuildSysPro.IBPSA.Fluid.HeatExchangers.HeaterCooler_u

# .BuildSysPro.IBPSA.Fluid.HeatExchangers.HeaterCooler_u

Heater or cooler with prescribed heat flow rate

## Information

Model for an ideal heater or cooler with prescribed heat flow rate to the medium.

This model adds heat in the amount of `Q_flow = u Q_flow_nominal` to the medium. The input signal `u` and the nominal heat flow rate `Q_flow_nominal` can be positive or negative. A positive value of `Q_flow` means heating, and negative means cooling.

The outlet conditions at `port_a` are not affected by this model, other than for a possible pressure difference due to flow friction.

Optionally, this model can have a flow resistance. Set `dp_nominal = 0` to disable the flow friction calculation.

For a model that uses as an input the fluid temperature leaving at `port_b`, use IBPSA.Fluid.HeatExchangers.PrescribedOutlet

#### Limitations

This model does not affect the humidity of the air. Therefore, if used to cool air below the dew point temperature, the water mass fraction will not change.

#### Validation

The model has been validated against the analytical solution in the example IBPSA.Fluid.HeatExchangers.Validation.HeaterCooler_u.

## Revisions

- October 13, 2022, by Fabian Wuellhorst:
  Added unit to instance `gai`.
  This is for #1642.
- March 7, 2022, by Michael Wetter:
  Removed `massDynamics`.
  This is for #1542.
- November 3, 2016, by Michael Wetter:
  Set `preHea(final alpha=0)` as this allows to simplify the system of equations.
  This is for #570.
- November 19, 2015, by Michael Wetter:
  Removed assignment of parameter `showDesignFlowDirection` in `extends` statement. This is for #349.
- May 6, 2015, by Michael Wetter:
  Set `prescribedHeatFlowRate=true`. This is for issue #412.
- May 1, 2015, by Marcus Fuchs:
  Corrected typo in documentation.
- November 12, 2014, by Michael Wetter:
  Added output signal `Q_flow` so that it has the same output ports as IBPSA.Fluid.HeatExchangers.Validation.PrescribedOutlet.
- September 11, 2014, by Christoph Nytsch-Geusen:
  Renaming class to `HeaterCooler_u`.
- October 15, 2013, by Michael Wetter:
  Redeclared the control volume to be final so that it does not show anymore in the parameter window.
- July 11, 2011, by Michael Wetter:
  Redeclared fluid volume as final. This prevents the fluid volume model to appear in the dialog window.
- May 24, 2011, by Michael Wetter:
  Changed base class to allow using the model as a dynamic or a steady-state model.
- April 17, 2008, by Michael Wetter:
  First implementation.

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