classVersion_0_9_0

Information

• Added the following heat exchanger models
  • Buildings.Fluid.HeatExchangers.DryEffectivenessNTU for a sensible heat exchanger that uses the epsilon-NTU relations to compute the heat transfer.
  • Buildings.Fluid.HeatExchangers.DryCoilCounterFlow and Buildings.Fluid.HeatExchangers.WetCoilCounterFlow to model a coil without and with water vapor condensation. These models approximate the coil as a counterflow heat exchanger.
• 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 multi-layer construction, and to allow individual material layers to be computed steady-state 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.