modelica - 在 Modelica 中正确使用 inStream()

Question

我正在尝试在 Modelica 中构建一个非常简单的分布式热流体体积模型，并且正在努力使用流运算符正确实现它。本卷使用 DryAirNasa 作为介质，我希望它没有海量存储、没有压降、也没有能量存储(很像 Modelica.Fluid.Pipes.StaticPipe 模型)。然而，我想明确地执行能量平衡，以便可以存在热传递相互作用。我也不想在此模型中定义质量流量，而是在连接到管道末端的边界之一中定义它(例如，Modelica.Fluid.Sources.MassFlowSource_h)。

我已经创建了此类模型的测试实现，但根据 Dymola 的说法，该模型显然缺少一个方程。对于如何修复此模型以使其正确的任何见解，我将不胜感激。如果我添加方程

port_a.h_outflow = Medium.specificEnthalpy(state_a)

对于方程部分，模型具有相同数量的方程和未知数，但我没有任何充分的理由来添加这样的方程。

 model AirFlowTemp

  // Objective: create a component that has no pressure drop, no mass storage,
   and no energy storage, but that has a heat input.

  import SI=Modelica.SIunits;

  final replaceable package Medium=Modelica.Media.Air.DryAirNasa;

  AirFlow.AirFlowPort port_a(redeclare package Medium
      = Medium);
  AirFlow.AirFlowPort port_b(redeclare package Medium
      = Medium);
  Interfaces.HeatPort heatPort;

  Medium.EnthalpyFlowRate[2] H_flow "enthalpy flow";
  SI.HeatFlowRate Q_flow "heat flow rate";

  Medium.Temperature T_mean;
  Medium.ThermodynamicState state_a;
  Medium.ThermodynamicState state_b;

equation 
  // no pressure drop across the component.
  port_a.p = port_b.p;

  // Assume that there is no mass storage in the volume
  0 = port_a.m_flow + port_b.m_flow;

  // Energy balance
  H_flow[1] = semiLinear(port_a.m_flow, inStream(port_a.h_outflow), inStream(port_b.h_outflow));
  H_flow[2] = semiLinear(port_b.m_flow, inStream(port_b.h_outflow), inStream(port_a.h_outflow));
  0 = Q_flow + H_flow[1] + H_flow[2];

  state_a = Medium.setState_ph(port_a.p, inStream(port_a.h_outflow));
  state_b = Medium.setState_ph(port_b.p, inStream(port_b.h_outflow));

  T_mean = (Medium.temperature(state_a) +
            Medium.temperature(state_b))/2;

  heatPort.Q_flow = Q_flow;
  heatPort.T = T_mean;

end AirFlowTemp;

connector AirFlowPort

  replaceable package Medium = Modelica.Media.Interfaces.PartialMedium;

  Medium.AbsolutePressure p;
  flow Medium.MassFlowRate m_flow;
  stream Medium.SpecificEnthalpy h_outflow;
  stream Medium.MassFraction Xi_outflow[Medium.nXi];

end AirFlowPort;


connector HeatPort
  extends Modelica.Thermal.HeatTransfer.Interfaces.HeatPort;
end HeatPort;

Answer 1

大约 4 周前，我在做同样的事情时遇到了同样的问题。尝试一下这是否可以作为更接近正确使用 inStream 的一步。

1. 删除Medium.EnthalpyFlowRate[2] H_flow“焓流量”SI.HeatFlowRate Q_flow "热流量";接口(interface).HeatPort heatPort；SI.HeatFlowRate Q_flow "热流量";介质.温度T_mean;T_mean = (中.温度(state_a) + 中.温度(state_b))/2;

   heatPort.Q_flow = Q_flow;heatPort.T = T_mean;=> 只是测试管道，没有 heatPort

2. 使用port_a.outflow*port_a.m_flow = inStream(port_b.outflow)*port_b.m_flow;port_b.outflow*port_b.m_flow = inStream(port_a.outflow)*port_a.m_flow;

而不是: H_flow[1] = semiLinear(port_a.m_flow, inStream(port_a.h_outflow), inStream(port_b.h_outflow)); H_flow[2] = semiLinear(port_b.m_flow, inStream(port_b.h_outflow), inStream(port_a.h_outflow)); 0 = Q_flow + H_flow[1] + H_flow[2];

1. 更改无热端口的测试

=>这有效吗？

问候乌韦