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;
最佳答案
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。
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
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];
- 更改无热端口的测试
=>这有效吗?
问候 乌韦
关于modelica - 在 Modelica 中正确使用 inStream(),我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/17867152/