Skip to content

Commit

Permalink
Updated user guide
Browse files Browse the repository at this point in the history
  • Loading branch information
mwetter committed Jul 13, 2015
1 parent 36d6d6b commit 51254b3
Show file tree
Hide file tree
Showing 6 changed files with 11 additions and 13 deletions.
Original file line number Diff line number Diff line change
Expand Up @@ -266,16 +266,15 @@ Consider the flow circuit shown below that consists of a pump or fan, a flow res

When this model is used with a medium model that models
:term:`compressible flow`, such as
the medium model `Buildings.Media.IdealGases.SimpleAir <http://simulationresearch.lbl.gov/modelica/releases/latest/help/Buildings_Media_IdealGases_SimpleAir.html#Buildings.Media.IdealGases.SimpleAir>`_,
the medium model `Buildings.Media.Air <http://simulationresearch.lbl.gov/modelica/releases/latest/help/Buildings_Media_Air.html#Buildings.Media.Air>`_,
then the model is well defined because the gas medium implements the
equation :math:`p=\rho \, R \, T`,
where :math:`p` is the static pressure, :math:`\rho` is the mass density,
:math:`R` is the gas constant and :math:`T` is the absolute temperature.

However, when the medium model is changed to a model that models
:term:`incompressible flow`, such as
`Buildings.Media.GasesConstantDensity.SimpleAir <http://simulationresearch.lbl.gov/modelica/releases/latest/help/Buildings_Media_GasesConstantDensity_SimpleAir.html#Buildings.Media.GasesConstantDensity.SimpleAir>`_ or
`Buildings.Media.ConstantPropertyLiquidWater <http://simulationresearch.lbl.gov/modelica/releases/latest/help/Buildings_Media_ConstantPropertyLiquidWater.html#Buildings.Media.ConstantPropertyLiquidWater>`_,
`Buildings.Media.Water <http://simulationresearch.lbl.gov/modelica/releases/latest/help/Buildings_Media_Water.html#Buildings.Media.Water>`_,
then the density is constant. Consequently, there is no equation that
can be used to compute the pressure based on the volume.
In this situation, attempting to translate the model leads, in Dymola, to the following error message:
Expand All @@ -288,7 +287,7 @@ In this situation, attempting to translate the model leads, in Dymola, to the fo
The number of scalar Real unknown elements are 58.
The number of scalar Real equation elements are 58.

Similarly, if the medium model `Modelica.Media.Water.WaterIF97OnePhase_ph <http://simulationresearch.lbl.gov/modelica/releases/msl/3.2/help/Modelica_Media_Water_WaterIF97OnePhase_ph.html#Modelica.Media.Water.WaterIF97OnePhase_ph>`_,
Similarly, if the medium model `Buildings.Media.Specialized.Water.TemperatureDependentDensity <http://simulationresearch.lbl.gov/modelica/releases/latest/help/Buildings_Media_Specialized_Water_TemperatureDependentDensity.html#Buildings.Media.Specialized.Water.TemperatureDependentDensity>`_,
which models density as a function of pressure and enthalpy, is used, then
the model is well-defined, but the pressure increases the longer the pump runs.
The reason is that the pump adds heat to the water. When the water temperature
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -39,10 +39,10 @@ To add a component of a thermofluid flow device, the package
See `Buildings.Fluid.Interface.UsersGuide <http://simulationresearch.lbl.gov/modelica/releases/latest/help/Buildings_Fluid_Interfaces_UsersGuide.html#Buildings.Fluid.Interfaces.UsersGuide>`_ for a description of these classes.
Alternatively, simple models such as the models below may be used as a starting point for implementing new models for thermofluid flow devices:

`Buildings.Fluid.HeatExchangers.HeaterCoolerPrescribed <http://simulationresearch.lbl.gov/modelica/releases/latest/help/Buildings_Fluid_HeatExchangers.html#Buildings.Fluid.HeatExchangers.HeaterCoolerPrescribed>`_
`Buildings.Fluid.HeatExchangers.HeaterCooler_u <http://simulationresearch.lbl.gov/modelica/releases/latest/help/Buildings_Fluid_HeatExchangers.html#Buildings.Fluid.HeatExchangers.HeaterCooler_u>`_
For a device that adds heat to a fluid stream.

`Buildings.Fluid.MassExchangers.HumidifierPrescribed <http://simulationresearch.lbl.gov/modelica/releases/latest/help/Buildings_Fluid_MassExchangers.html#Buildings.Fluid.MassExchangers.HumidifierPrescribed>`_
`Buildings.Fluid.MassExchangers.Humidifier_u <http://simulationresearch.lbl.gov/modelica/releases/latest/help/Buildings_Fluid_MassExchangers.html#Buildings.Fluid.MassExchangers.Humidifier_u>`_
For a device that adds humidity to a fluid stream.

`Buildings.Fluid.Chillers.Carnot <http://simulationresearch.lbl.gov/modelica/releases/latest/help/Buildings_Fluid_Chillers.html#Buildings.Fluid.Chillers.Carnot>`_
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -406,15 +406,14 @@ <h3>2.4.3. Use of sensors in fluid flow systems<a class="headerlink" href="#use-
</div>
<p>When this model is used with a medium model that models
<a class="reference internal" href="glossary.html#term-compressible-flow"><em class="xref std std-term">compressible flow</em></a>, such as
the medium model <a class="reference external" href="http://simulationresearch.lbl.gov/modelica/releases/latest/help/Buildings_Media_IdealGases_SimpleAir.html#Buildings.Media.IdealGases.SimpleAir">Buildings.Media.IdealGases.SimpleAir</a>,
the medium model <a class="reference external" href="http://simulationresearch.lbl.gov/modelica/releases/latest/help/Buildings_Media_Air.html#Buildings.Media.Air">Buildings.Media.Air</a>,
then the model is well defined because the gas medium implements the
equation <span class="math">\(p=\rho \, R \, T\)</span>,
where <span class="math">\(p\)</span> is the static pressure, <span class="math">\(\rho\)</span> is the mass density,
<span class="math">\(R\)</span> is the gas constant and <span class="math">\(T\)</span> is the absolute temperature.</p>
<p>However, when the medium model is changed to a model that models
<a class="reference internal" href="glossary.html#term-incompressible-flow"><em class="xref std std-term">incompressible flow</em></a>, such as
<a class="reference external" href="http://simulationresearch.lbl.gov/modelica/releases/latest/help/Buildings_Media_GasesConstantDensity_SimpleAir.html#Buildings.Media.GasesConstantDensity.SimpleAir">Buildings.Media.GasesConstantDensity.SimpleAir</a> or
<a class="reference external" href="http://simulationresearch.lbl.gov/modelica/releases/latest/help/Buildings_Media_ConstantPropertyLiquidWater.html#Buildings.Media.ConstantPropertyLiquidWater">Buildings.Media.ConstantPropertyLiquidWater</a>,
<a class="reference external" href="http://simulationresearch.lbl.gov/modelica/releases/latest/help/Buildings_Media_Water.html#Buildings.Media.Water">Buildings.Media.Water</a>,
then the density is constant. Consequently, there is no equation that
can be used to compute the pressure based on the volume.
In this situation, attempting to translate the model leads, in Dymola, to the following error message:</p>
Expand All @@ -425,7 +424,7 @@ <h3>2.4.3. Use of sensors in fluid flow systems<a class="headerlink" href="#use-
The number of scalar Real equation elements are 58.
</pre></div>
</div>
<p>Similarly, if the medium model <a class="reference external" href="http://simulationresearch.lbl.gov/modelica/releases/msl/3.2/help/Modelica_Media_Water_WaterIF97OnePhase_ph.html#Modelica.Media.Water.WaterIF97OnePhase_ph">Modelica.Media.Water.WaterIF97OnePhase_ph</a>,
<p>Similarly, if the medium model <a class="reference external" href="http://simulationresearch.lbl.gov/modelica/releases/latest/help/Buildings_Media_Specialized_Water_TemperatureDependentDensity.html#Buildings.Media.Specialized.Water.TemperatureDependentDensity">Buildings.Media.Specialized.Water.TemperatureDependentDensity</a>,
which models density as a function of pressure and enthalpy, is used, then
the model is well-defined, but the pressure increases the longer the pump runs.
The reason is that the pump adds heat to the water. When the water temperature
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -141,9 +141,9 @@ <h3>5.2.1. Thermofluid flow device<a class="headerlink" href="#thermofluid-flow-
See <a class="reference external" href="http://simulationresearch.lbl.gov/modelica/releases/latest/help/Buildings_Fluid_Interfaces_UsersGuide.html#Buildings.Fluid.Interfaces.UsersGuide">Buildings.Fluid.Interface.UsersGuide</a> for a description of these classes.
Alternatively, simple models such as the models below may be used as a starting point for implementing new models for thermofluid flow devices:</p>
<dl class="docutils">
<dt><a class="reference external" href="http://simulationresearch.lbl.gov/modelica/releases/latest/help/Buildings_Fluid_HeatExchangers.html#Buildings.Fluid.HeatExchangers.HeaterCoolerPrescribed">Buildings.Fluid.HeatExchangers.HeaterCoolerPrescribed</a></dt>
<dt><a class="reference external" href="http://simulationresearch.lbl.gov/modelica/releases/latest/help/Buildings_Fluid_HeatExchangers.html#Buildings.Fluid.HeatExchangers.HeaterCooler_u">Buildings.Fluid.HeatExchangers.HeaterCooler_u</a></dt>
<dd>For a device that adds heat to a fluid stream.</dd>
<dt><a class="reference external" href="http://simulationresearch.lbl.gov/modelica/releases/latest/help/Buildings_Fluid_MassExchangers.html#Buildings.Fluid.MassExchangers.HumidifierPrescribed">Buildings.Fluid.MassExchangers.HumidifierPrescribed</a></dt>
<dt><a class="reference external" href="http://simulationresearch.lbl.gov/modelica/releases/latest/help/Buildings_Fluid_MassExchangers.html#Buildings.Fluid.MassExchangers.Humidifier_u">Buildings.Fluid.MassExchangers.Humidifier_u</a></dt>
<dd>For a device that adds humidity to a fluid stream.</dd>
<dt><a class="reference external" href="http://simulationresearch.lbl.gov/modelica/releases/latest/help/Buildings_Fluid_Chillers.html#Buildings.Fluid.Chillers.Carnot">Buildings.Fluid.Chillers.Carnot</a></dt>
<dd>For a device that exchanges heat between two fluid streams.</dd>
Expand Down
Binary file not shown.
Loading

0 comments on commit 51254b3

Please sign in to comment.