This section summarizes the changes that have been performed
on the Buildings library

Version 0.10.0 (July 30, 2010)

Version 0.9.0 (June 11, 2010)

Version 0.8.0 (February 6, 2010)

Version 0.7.0 (September 29, 2009)

Version 0.6.0 (May 15, 2009)

Version 0.5.0 (February 19, 2009)

Version 0.4.0 (October 31, 2008)


Version 0.3.0 (September 30, 2008)

Version 0.2.0 (June 17, 2008)

Version 0.1.0 (May 27, 2008)
Package Content
The following critical error has been fixed (i.e. error
that can lead to wrong simulation results):

Added the following heat exchanger models

Revised air damper
Buildings.Fluid.Actuators.BaseClasses.exponentialDamper.
The new implementation avoids warnings and leads to faster convergence
since the solver does not attempt anymore to solve for a variable that
needs to be strictly positive.

Revised package
Buildings.Fluid.Movers
to allow zero flow for some pump or fan models.
If the input to the model is the control signal
y
, then
the flow is equal to zero if y=0
. This change required rewriting
the package to avoid division by the rotational speed.

Revised package
Buildings.HeatTransfer
to include a model for a multilayer construction, and to
allow individual material layers to be computed steadystate or
transient.

In package
Buildings.Fluid, changed models so that
if the parameter
dp_nominal
is set to zero,
then the pressure drop equation is removed. This allows, for example,
to model a heating and a cooling coil in series, and lump there pressure drops
into a single element, thereby reducing the dimension of the nonlinear system
of equations.

Added model
Buildings.Controls.Continuous.LimPID, which is identical to
Modelica.Blocks.Continuous.LimPID, except that it
allows reverse control action. This simplifies use of the controller
for cooling applications.

Added model
Buildings.Fluid.Actuators.Dampers.MixingBox for an outside air
mixing box with air dampers.

Changed implementation of flow resistance in
Buildings.Fluid.Actuators.Dampers.MixingBoxMinimumFlow. Instead of using a
fixed resistance and a damper model in series, only one model is used
that internally adds these two resistances. This leads to smaller systems
of nonlinear equations.

Changed
Buildings.Media.PerfectGases.MoistAir.T_phX (and by inheritance all
other moist air medium models) to first compute
T
in closed form assuming no saturation. Then, a check is done to determine
whether the state is in the fog region. If the state is in the fog region,
then Internal.solve
is called. This new implementation
can lead to significantly shorter computing
time in models that frequently call T_phX
.

Added package
Buildings.Media.GasesConstantDensity which contains medium models
for dry air and moist air.
The use of a constant density avoids having pressure as a state variable in mixing volumes. Hence, fast transients
introduced by a change in pressure are avoided.
The drawback is that the dimensionality of the coupled
nonlinear equation system is typically larger for flow
networks.

In
Buildings.Fluid.Actuators.BaseClasses.PartialDamperExponential,
added default value for parameter
A
to avoid compilation error
if the parameter is disabled but not specified.

Simplified the mixing volumes in
Buildings.Fluid.MixingVolumes by removing the port velocity,
pressure drop and height.

In
Buildings.Fluid.Interfaces.PartialLumpedVolume,
added to
Medium.BaseProperties
the initialization
X(start=X_start[1:Medium.nX])
. Previously, the initialization
was only done for Xi
but not for X
, which caused the
medium to be initialized to reference_X
, ignoring the value of X_start
.

Renamed
Buildings.Media.PerfectGases.MoistAirNonSaturated
to
Buildings.Media.PerfectGases.MoistAirUnsaturated
and Buildings.Media.GasesPTDecoupled.MoistAirNoLiquid
to
Buildings.Media.GasesPTDecoupled.MoistAirUnsaturated,
and added assert
statements if saturation occurs.

Added regularizaation near zero flow to
Buildings.Fluid.HeatExchangers.ConstantEffectiveness
and
Buildings.Fluid.MassExchangers.ConstantEffectiveness.

Fixed bug regarding temperature offset in
Buildings.Media.PerfectGases.MoistAirUnsaturated.T_phX.

Added implementation of function
Buildings.Media.GasesPTDecoupled.MoistAirUnsaturated.enthalpyOfNonCondensingGas and its derivative.

In
Buildings.Media.PerfectGases.MoistAir, fixed
bug in implementation of
Buildings.Media.PerfectGases.MoistAir.T_phX. In the
previous version, it computed the inverse of its parent class,
which gave slightly different results.

In
Buildings.Utilities.IO.BCVTB.BCVTB, added parameter to specify
the value to be sent to the BCVTB at the first data exchange,
and added parameter that deactivates the interface. Deactivating
the interface is sometimes useful during debugging.

In
Buildings.Media.GasesPTDecoupled.MoistAir and in
Buildings.Media.PerfectGases.MoistAir, added function
enthalpyOfNonCondensingGas and its derivative.

In
Buildings.Media,
fixed bug in implementations of derivatives.

Added model
Buildings.Fluid.Storage.ExpansionVessel.

Added Wrapper function
Buildings.Fluid.Movers.BaseClasses.Characteristics.solve for
Modelica.Math.Matrices.solve. This is currently needed since
Modelica.Math.Matrices.solve does not specify a
derivative.

Fixed bug in
Buildings.Fluid.Storage.Stratified.
In the previous version,
for computing the heat conduction between the top (or bottom) segment and
the outside,
the whole thickness of the water volume was used
instead of only half the thickness.

In
Buildings.Media.ConstantPropertyLiquidWater, added the option to specify a compressibility.
This can help reducing the size of the coupled nonlinear system of equations, at
the expense of introducing stiffness. This change required to change the inheritance
tree of the medium. Its base class is now
Buildings.Media.Interfaces.PartialSimpleMedium,
which contains the equation for the compressibility. The default setting will model
the flow as incompressible.

In
Buildings.Controls.Continuous.Examples.PIDHysteresis
and
Buildings.Controls.Continuous.Examples.PIDHysteresisTimer,
fixed error in default parameter
eOn
.
Fixed error by introducing parameter Td
,
which used to be hardwired in the PID controller.

Added more models for fans and pumps to the package
Buildings.Fluid.Movers.
The models are similar to the ones in
Modelica.Fluid.Machines but have been adapted for
airbased systems, and to include more characteristic curves
in
Buildings.Fluid.Movers.BaseClasses.Characteristics.
The new models are better suited than the existing fan model
Buildings.Fluid.Movers.FlowMachinePolynomial for zero flow rate.

Added an optional mixing volume to
Buildings.Fluid.BaseClasses.PartialThreeWayResistance
and hence to the flow splitter and to the threeway valves. This often breaks algebraic loops and provides a state for the temperature if the mass flow rate goes to zero.

Added package Buildings.Fluid.Sources.
The package contains models for modeling species that
do not affect the medium balance of volumes. This can be used to track
for example carbon dioxide or other species that have a small concentration.

The package Buildings.Fluid.Actuators.Motors has been added.
The package contains a motor model for valves and dampers.

The package Buildings.Media has been reorganized and
the new medium model
Buildings.Media.GasesPTDecoupled.MoistAir
has been added.
In addition, this package now contains a bug fix that is needed for Modelica 2.2.1 and 2.2.2.
The bugs are fixed by using a new
base class
Buildings.Media.Interfaces.PartialSimpleIdealGasMedium
(that fixes the bugs) instead of
Modelica.Media.Interfaces.PartialSimpleIdealGasMedium.
In the original implementation, initial states of fluid volumes can be far away from
the steadystate value because of an inconsistent implementation of the the enthalpy
and internal energy.
When the Buildings library is upgraded to
to Modelica 3.0.0, it should be safe to remove this bug fix.

The package Buildings.Fluid.HeatExchangers
has been revised and several models have been renamed.
The heat exchanger models have been revised to allow computing the fluid volumes either
dynamically, or in steadystate.

The damper with exponential opening characteristic has been revised to allow control signals
over the whole range between 0 and 1. This was in earlier versions restricted.
In the same model, a bug was fixed that caused the flow to be largest for y=0, i.e., when the damper is closed.

Additional models for psychrometric equations have been added. The new models contain equations
that convert dew point temperature and water vapor pressure, as well
as water vapor concentration and water vapor pressure.

A new mixing volume has been added that allows latent heat exchange with the volume.
This model can be used to model a volume of moist air with water vapor condensation
inside the volume. The condensate is removed from the volume in its liquid phase.
New in this version are models for two and three way valves.
In addition, the Fluids package has been slightly revised.
The package Fluid.BaseClasses has been added because in
the previous version, partial models for fixed resistances
where part of the Actuator package.
First release of the library.
This version contains basic models for modeling building HVAC systems.
It also contains new medium models in the package
Buildings.Media. These medium models
have simpler property functions than the ones from
Modelica.Media. For example,
there is medium model with constant heat capacity which is often sufficiently
accurate for building HVAC simulation, in contrast to the more detailed models
from Modelica.Media that are valid in
a larger temperature range, at the expense of introducing nonlinearities due
to the medium properties.
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