modelHydraulicResistance
Extends from AixLib.Fluid.BaseClasses.PartialResistance (Partial model for a hydraulic resistance).
Information
Overview
Simple model for a hydraulic resistance with the pressureloss
modelled with the pressure loss factor zeta (ζ).
Concept
Values for pressure loss factor zeta can be easily found in tables.
The following equation represents the dependencies of
m_flow(_nominal), dp(_nominal), zeta and the
diameter (D).
Δp = 0.5*ζ*ρ*v*|v|
= 8*ζ/(π^2*D^4*ρ) * m_flow*|m_flow|
Since this a simplified approach to calculate/generate a pressure
drop, there exist no distinction between laminar and turbulent flow
regarding ζ-values.
The non-existance of a turbulent flow, the equation handling near zero as well as the different approach of being able to use tabled zeta values, mainly distinguish this model from AixLib.Fluid.FixedResistances.PressureDrop.
Example Results
AixLib.Fluid.FixedResistances.Examples.CompareFixedResistances
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Boolean | homotopyInitialization (from PartialResistance) | true | = true, use homotopy method |
| Modelica.Units.SI.MassFlowRate | m_flow_turbulent (from PartialResistance) | Turbulent flow if |m_flow| >= m_flow_turbulent | |
| Real | zeta | Pressure loss factor for flow of port_a -> port_b | |
| Modelica.Units.SI.Diameter | diameter | Diameter of component | |
| Assumptions | |||
| Boolean | allowFlowReversal (from PartialTwoPort) | true | = false to simplify equations, assuming, but not enforcing, no flow reversal |
| Nominal condition | |||
| Modelica.Units.SI.MassFlowRate | m_flow_nominal (from PartialTwoPortInterface) | Nominal mass flow rate | |
| Modelica.Units.SI.PressureDifference | dp_nominal (from PartialResistance) | Pressure drop at nominal mass flow rate | |
| Advanced | |||
| Modelica.Units.SI.MassFlowRate | m_flow_small (from PartialTwoPortInterface) | 1E-4*abs(m_flow_nominal) | Small mass flow rate for regularization of zero flow |
| Boolean | from_dp (from PartialResistance) | false | = true, use m_flow = f(dp) else dp = f(m_flow) |
| Boolean | linearized (from PartialResistance) | false | = true, use linear relation between m_flow and dp for any flow rate |
| Modelica.Units.SI.PressureDifference | dp_start | 0 | Guess value of dp = port_a.p - port_b.p |
| Medium.MassFlowRate | m_flow_start | 0 | Guess value of m_flow = port_a.m_flow |
| Advanced › Diagnostics | |||
| Boolean | show_T (from PartialTwoPortInterface) | false | = true, if actual temperature at port is computed |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Fluid.Interfaces.FluidPort_a | port_a (from PartialTwoPort) | Fluid connector a (positive design flow direction is from port_a to port_b) | |
| Modelica.Fluid.Interfaces.FluidPort_b | port_b (from PartialTwoPort) | Fluid connector b (positive design flow direction is from port_a to port_b) |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Units.SI.MassFlowRate | m_flow (from PartialTwoPortInterface) | port_a.m_flow | Mass flow rate from port_a to port_b (m_flow > 0 is design flow direction) |
| Modelica.Units.SI.PressureDifference | dp (from PartialTwoPortInterface) | port_a.p - port_b.p | Pressure difference between port_a and port_b |
| Medium.ThermodynamicState | sta_a (from PartialTwoPortInterface) | if allowFlowReversal then Medium.setState_phX(port_a.p, noEvent(actualStream(port_a.h_outflow)), noEvent(actualStream(port_a.Xi_outflow))) else Medium.setState_phX(port_a.p, noEvent(inStream(port_a.h_outflow)), noEvent(inStream(port_a.Xi_outflow))) | Medium properties in port_a |
| Medium.ThermodynamicState | sta_b (from PartialTwoPortInterface) | if allowFlowReversal then Medium.setState_phX(port_b.p, noEvent(actualStream(port_b.h_outflow)), noEvent(actualStream(port_b.Xi_outflow))) else Medium.setState_phX(port_b.p, noEvent(port_b.h_outflow), noEvent(port_b.Xi_outflow)) | Medium properties in port_b |
Revisions
-
April 27, 2017 by Philipp Mehrfeld:
Model acc. to IBPSA conventions. Take into account homotopyInit., linearization, from_dp. -
April 2016 by Peter Matthes:
Improved formulation of flow equation according to issue #232. -
November 2014 by Marcus Fuchs:
Changed model to use Annex 60 base class -
November 1, 2013 by Ana Constantin:
Implemented