modelPipeStandard
Pipe model parameterized with hydraulic diameter
Extends from Buildings.Fluid.FixedResistances.HydraulicDiameter (Fixed flow resistance with hydraulic diameter and m_flow as parameter).
Information
This model is similar to Buildings.Fluid.FixedResistances.HydraulicDiameter except that a binding equation is provided to compute the nominal fluid velocity from the hydraulic diameter (as opposed to the hydraulic diameter being computed from the nominal fluid velocity in the original model).
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 | k (from PressureDrop) | if computeFlowResistance and not (linearized or fullyLaminar) then m_flow_nominal_pos/dp_nominal_pos^(1/n) else 0 | Flow coefficient, k=m_flow/dp^(1/n) |
| Modelica.Units.SI.Length | dh (from HydraulicDiameter) | sqrt(4*m_flow_nominal/rho_default/v_nominal/Modelica.Constants.pi) | Hydraulic diameter (assuming a round cross section area) |
| Modelica.Units.SI.Length | length (from HydraulicDiameter) | Length of the pipe | |
| Real | ReC (from HydraulicDiameter) | 4000 | Reynolds number where transition to turbulence starts |
| Modelica.Units.SI.Length | roughness (from HydraulicDiameter) | 2.5e-5 | Absolute roughness of pipe, with a default for a smooth steel pipe (dummy if use_roughness = false) |
| Real | fac (from HydraulicDiameter) | 2 | Factor to take into account resistance of bends etc., fac=dp_nominal/dpStraightPipe_nominal |
| Modelica.Units.SI.PressureDifference | dpStraightPipe_nominal (from HydraulicDiameter) | Modelica.Fluid.Pipes.BaseClasses.WallFriction.Detailed.pressureLoss_m_flow(m_flow = m_flow_nominal, rho_a = rho_default, rho_b = rho_default, mu_a = mu_default, mu_b = mu_default, length = length, diameter = dh, roughness = roughness, m_flow_small = m_flow_small) | Pressure loss of a straight pipe at m_flow_nominal |
| 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 | |
| Modelica.Units.SI.Velocity | v_nominal (from HydraulicDiameter) | if rho_default < 500 then 1.5 else 0.15 | Velocity at m_flow_nominal (used to compute default value for hydraulic diameter dh) |
| 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) |
| Real | n (from PartialResistance) | 2 | Flow exponent, n=1 for laminar, n=2 for turbulent |
| Boolean | linearized (from PartialResistance) | false | = true, use linear relation between m_flow and dp for any flow rate |
| Boolean | disableComputeFlowResistance (from HydraulicDiameter) | false | =false to disable computation of flow resistance |
| Advanced › Diagnostics | |||
| Boolean | show_T (from PartialTwoPortInterface) | false | = true, if actual temperature at port is computed |
| Transition to laminar | |||
| Real | deltaM (from PressureDrop) | 0.3 | Fraction of nominal mass flow rate where transition to turbulent occurs |
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 |
| Modelica.Units.SI.Velocity | v (from HydraulicDiameter) | m_flow/(rho_default*ARound) | Flow velocity (assuming a round cross section area) |
Revisions
-
February 23, 2021, by Antoine Gautier:
First implementation.