.Buildings.Fluid.Actuators.BaseClasses.ValveParameters

Information

Model that computes the flow coefficients of valves. This base class allows the following modeling options, which have been adapted from the valve implementation in Modelica.Fluid to specify the valve flow coefficient in fully open conditions:

• CvData = Buildings.Fluid.Types.CvTypes.Av: the flow coefficient is given by the metric Av coefficient (m^2).
• CvData = Buildings.Fluid.Types.CvTypes.Kv: the flow coefficient is given by the metric Kv coefficient (m^3/h).
• CvData = Buildings.Fluid.Types.CvTypes.Cv: the flow coefficient is given by the US Cv coefficient (USG/min).
• CvData = Buildings.Fluid.Types.CvTypes.OpPoint: the flow is computed from the nominal operating point specified by dp_nominal and m_flow_nominal.

The treatment of parameters Kv and Cv is explained in detail in the Users Guide.

In contrast to the model in Modelica.Fluid, this model uses the protected parameter Kv_SI, which is the flow coefficient in SI units, i.e., it is the ratio between mass flow rate in kg/s and square root of pressure drop in Pa. The value of Kv_SI is computed based on the parameters Av, Kv, Cv, or, if CvData = Buildings.Fluid.Types.CvTypes.OpPoint, based on m_flow_nominal and dpValve_nominal. Conversely, if CvData <> Buildings.Fluid.Types.CvTypes.OpPoint, then dpValve_nominal is computed based on Av, Kv, or Cv, and the nominal mass flow rate m_flow_nominal. Therefore, if CvData <> Buildings.Fluid.Types.CvTypes.OpPoint, then specifying a value for dpValve_nominal is a syntax error.

Revisions

• January 22, 2016, by Michael Wetter:
  Corrected type declaration of pressure difference. This is for #404.
• August 12, 2014, by Michael Wetter:
  Changed attribute min of dpValve_nominal to 0. This is needed as for example in Buildings.Fluid.Actuators.Valves.Examples.TwoWayValveTable, dpValve_nominal=0.
• August 8, 2014, by Michael Wetter:
  Changed the initial algorithm to an initial equation section. Otherwise, OpenModelica attempts to solve for the parameter values using numerical iteration, and fails in doing so.
• May 29, 2014, by Michael Wetter:
  Removed undesirable annotation Evaluate=true.
• March 25, 2013, by Michael Wetter:
  Removed stray backslash in write statement.
• February 28, 2013, by Michael Wetter:
  Reformulated assignment of parameters, and removed Kv_SI as a public parameter because it is always computed based on other parameters. This change avoids a translation error in Dymola 2014 beta1 in the pedantic mode, and a translation warning otherwise.
• February 18, 2009 by Michael Wetter:
  First implementation.