.BuildSysPro.IBPSA.Fluid.BaseClasses.FlowModels.basicFlowFunction_m_flow

Information

Function that computes the pressure drop of flow elements as

Δp = sign(ṁ) (ṁ ⁄ k)²

with regularization near the origin. Therefore, the flow coefficient is

k = ṁ ⁄ √ Δp  

The input m_flow_turbulent determines the location of the regularization.

Interface

function basicFlowFunction_m_flow
  input Modelica.Units.SI.MassFlowRate m_flow "Mass flow rate in design flow direction";
  input Real k(unit = "") "Flow coefficient, k=m_flow/sqrt(dp), with unit=(kg.m)^(1/2)";
  input Modelica.Units.SI.MassFlowRate m_flow_turbulent(min = 0) "Mass flow rate where transition to turbulent flow occurs";
  output Modelica.Units.SI.PressureDifference dp(displayUnit = "Pa") "Pressure difference between port_a and port_b (= port_a.p - port_b.p)";
end basicFlowFunction_m_flow;

Revisions

• December 9, 2019, by Michael Wetter:
  Added smooth(2, . ), similar to IBPSA.Fluid.BaseClasses.FlowModels.basicFlowFunction_dp.
  See #1240.
• January 4, 2019, by Michael Wetter:
  Set `Inline=false`.
  See #1070.
• May 1, 2017, by Filip Jorissen:
  Revised implementation such that IBPSA.Fluid.BaseClasses.FlowModels.basicFlowFunction_m_flow is C2 continuous. See #725.
• January 22, 2016, by Michael Wetter:
  Corrected type declaration of pressure difference. This is for #404.
• July 28, 2015, by Michael Wetter:
  Removed double declaration of smooth(..) and smoothOrder and changed Inline=true to LateInline=true. This is for issue 301.
• July 15, 2015, by Filip Jorissen:
  New, more efficient implementation based on regularisation using simple polynomial. Expanded common subexpressions for function inlining to be possible. Set Inline=true for inlining to occur. This is for #279.
• August 10, 2011, by Michael Wetter:
  Removed if-then optimization that set dp=0 if m_flow=0, as this causes the derivative to be discontinuous at m_flow=0.
• August 4, 2011, by Michael Wetter:
  Removed option to use a linear function. The linear implementation is now done in models that call this function. With the previous implementation, the symbolic processor may not rearrange the equations, which can lead to coupled equations instead of an explicit solution.
• April 13, 2009, by Michael Wetter:
  First implementation.