Pump hydraulic efficiency constraint #3469

MatthiasEckhart · 2023-08-04T19:42:18Z

MatthiasEckhart
Aug 4, 2023

Dear All,

I am trying to model a coupled-tanks system, which is composed of two water tanks, a basin, two valves, and a centrifugal pump.

The pump has the following p-Q characteristics:

In my previous post, I have asked about the pump parameterization. My current pump data model is as follows:

record M510S_Data_4
  "Pump data for a TCS micropumps M510 pump"
  extends Buildings.Fluid.Movers.Data.Generic(
    pressure(V_flow=({0.0, 8.0}/60)*0.001, dp={-8/(-(8/0.7)), 0/(-(8/0.7))}*100000)
  );
 
 parameter Integer speed_rpm_nominal = 10000 "Nominal RPM";
 
  annotation (
defaultComponentPrefixes="parameter",
defaultComponentName="per",
Documentation(info=""));
end M510S_Data_4;

Note that I am primarily interested in the liquid levels of Tank 1 and Tank 2. Power characteristics etc. of the pump are not important in my scenario.

Coupled-Tanks Model: I have parameterized the model (to some extent) based on the dimensions of the components implemented as part of a physical testbed. As a first step, I have ignored the controller and set the pump to full speed.

model M510S_33_MBL

parameter Modelica.Units.SI.Density rho_default_this=Medium.density(state_default_this)
    "Density at nominal condition";
parameter Medium.ThermodynamicState state_default_this=
    Medium.setState_pTX(
      T=Medium.T_default,
      p=Medium.p_default,
      X=Medium.X_default[1:Medium.nXi]) "Default state";
      
parameter Modelica.Units.SI.Velocity v_nominal_this=0.15
    "Velocity at m_flow_nominal (used to compute default diameter)";
      
         parameter Modelica.Units.SI.MassFlowRate m_flow_nominal=2
    "Nominal mass flow rate for each fan";
  parameter Modelica.Units.SI.PressureDifference dp_nominal=500
    "Nominal pressure head for each fan";
      
package Medium = Buildings.Media.Water;
  Buildings.Fluid.Movers.SpeedControlled_y pump1(redeclare package Medium = Medium, redeclare replaceable
      M510S_Data_4 per,
      energyDynamics=Modelica.Fluid.Types.Dynamics.SteadyState,
      addPowerToMedium=false) annotation(
    Placement(visible = true, transformation(origin = {52, -70}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
   Modelica.Blocks.Sources.Constant rpm1(k= 10000) "Pump speed control signal"
    annotation (Placement(visible = true, transformation(extent = {{18, -26}, {30, -14}}, rotation = 0)));
  inner Modelica.Fluid.System system annotation(
    Placement(visible = true, transformation(origin = {100, 166}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
  Modelica.Blocks.Math.Gain gain1(k = 1 / M510S_Data_4.speed_rpm_nominal) annotation(
    Placement(visible = true, transformation(origin = {87, -37}, extent = {{-7, -7}, {7, 7}}, rotation = 0)));
    Modelica.Fluid.Vessels.OpenTank tank1(redeclare package Medium = Medium, crossArea = 0.74832, height = 0.278, level_start = 0, nPorts = 2, portsData = {Modelica.Fluid.Vessels.BaseClasses.VesselPortsData(diameter = 0.006), Modelica.Fluid.Vessels.BaseClasses.VesselPortsData(diameter = 0.006)}, use_portsData = true)  annotation(
    Placement(visible = true, transformation(origin = {-52, 170}, extent = {{-20, -20}, {20, 20}}, rotation = 0)));
    Modelica.Fluid.Vessels.OpenTank tank2(redeclare package Medium = Medium, crossArea = 0.74832, height = 0.278, level_start = 0, nPorts = 2, portsData = {Modelica.Fluid.Vessels.BaseClasses.VesselPortsData(diameter = 0.006), Modelica.Fluid.Vessels.BaseClasses.VesselPortsData(diameter = 0.006)}, use_portsData = true)  annotation(
    Placement(visible = true, transformation(origin = {-66, 52}, extent = {{-20, -20}, {20, 20}}, rotation = 0)));
  Buildings.Fluid.Actuators.Valves.TwoWayLinear val1(redeclare package Medium = Medium,
    l=0.05,
    m_flow_nominal=2,
    use_inputFilter=false,
    dpValve_nominal=6000) annotation(
    Placement(visible = true, transformation(origin = {-64, 124}, extent = {{-10, -10}, {10, 10}}, rotation = -90)));
  Buildings.Fluid.Actuators.Valves.TwoWayLinear val2(redeclare package Medium = Medium,
    l=0.05,
    m_flow_nominal=2,
    use_inputFilter=false,
    dpValve_nominal=6000) annotation(
    Placement(visible = true, transformation(origin = {-68, 12}, extent = {{-10, -10}, {10, 10}}, rotation = -90)));
    Modelica.Blocks.Sources.Ramp y(
    
    duration= 0,height=1,
    offset=0) "Control signal"
                 annotation (Placement(visible = true, transformation(extent = {{16, 106}, {36, 126}}, rotation = 0)));
    Modelica.Fluid.Vessels.OpenTank basin1(redeclare package Medium = Medium, crossArea = 4.4156, height = 0.12, level_start = 0.05, nPorts = 2, portsData = {Modelica.Fluid.Vessels.BaseClasses.VesselPortsData(diameter = 0.006), Modelica.Fluid.Vessels.BaseClasses.VesselPortsData(diameter = 0.006)}, use_portsData = true) annotation(
    Placement(visible = true, transformation(origin = {-68, -58}, extent = {{-20, -20}, {20, 20}}, rotation = 0)));
  Buildings.Fluid.FixedResistances.Pipe pip1(redeclare package Medium = Medium, lambdaIns = 0, length = 0.12, m_flow_nominal = 0.006 ^ 2 * Modelica.Constants.pi * v_nominal_this * rho_default_this / 4, nSeg = 1, thicknessIns = 0.002) annotation(
    Placement(visible = true, transformation(origin = {-66, 96}, extent = {{-10, -10}, {10, 10}}, rotation = -90)));
  Buildings.Fluid.FixedResistances.Pipe pip4(redeclare package Medium = Medium, lambdaIns = 0, length = 2.68, m_flow_nominal = 0.006 ^ 2 * Modelica.Constants.pi * v_nominal_this * rho_default_this / 4, nSeg = 1, thicknessIns = 0.002) annotation(
    Placement(visible = true, transformation(origin = {116, -70}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
  Buildings.Fluid.FixedResistances.Pipe pip3(redeclare package Medium = Medium, lambdaIns = 0, length = 0.605, m_flow_nominal = 0.006 ^ 2 * Modelica.Constants.pi * v_nominal_this * rho_default_this / 4, nSeg = 1, thicknessIns = 0.002) annotation(
    Placement(visible = true, transformation(origin = {-2, -78}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
  Buildings.Fluid.FixedResistances.Pipe pip2(redeclare package Medium = Medium, lambdaIns = 0, length = 0.45, m_flow_nominal = 0.006 ^ 2 * Modelica.Constants.pi * v_nominal_this * rho_default_this / 4, nSeg = 1, thicknessIns = 0.002) annotation(
    Placement(visible = true, transformation(origin = {-68, -16}, extent = {{-10, -10}, {10, 10}}, rotation = -90)));

equation
  connect(rpm1.y, gain1.u) annotation(
    Line(points = {{31, -20}, {67.1, -20}, {67.1, -37}, {79, -37}}, color = {0, 0, 127}));
  connect(gain1.y, pump1.y) annotation(
    Line(points = {{95, -37}, {52, -37}, {52, -58}}, color = {0, 0, 127}));
  connect(y.y, val1.y) annotation(
    Line(points = {{37, 116}, {9.5, 116}, {9.5, 124}, {-52, 124}}, color = {0, 0, 127}));
  connect(val1.port_a, tank1.ports[1]) annotation(
    Line(points = {{-64, 134}, {-64, 142}, {-52, 142}, {-52, 150}}, color = {0, 127, 255}));
  connect(y.y, val2.y) annotation(
    Line(points = {{37, 116}, {-0.5, 116}, {-0.5, 72}, {0, 72}, {0, 13}, {-56, 13}, {-56, 12}}, color = {0, 0, 127}));
  connect(tank2.ports[1], val2.port_a) annotation(
    Line(points = {{-66, 32}, {-68, 32}, {-68, 22}}, color = {0, 127, 255}));
  connect(pip1.port_b, tank2.ports[2]) annotation(
    Line(points = {{-66, 86}, {-66, 32}}, color = {0, 127, 255}));
  connect(val1.port_b, pip1.port_a) annotation(
    Line(points = {{-64, 114}, {-66, 114}, {-66, 106}}, color = {0, 127, 255}));
  connect(pip4.port_b, tank1.ports[2]) annotation(
    Line(points = {{126, -70}, {150.5, -70}, {150.5, 150}, {-52, 150}}, color = {0, 127, 255}));
  connect(basin1.ports[1], pip3.port_a) annotation(
    Line(points = {{-68, -78}, {-12, -78}}, color = {0, 127, 255}));
  connect(pip2.port_b, basin1.ports[2]) annotation(
    Line(points = {{-68, -26}, {-68, -78}}, color = {0, 127, 255}));
  connect(val2.port_b, pip2.port_a) annotation(
    Line(points = {{-68, 2}, {-68, -6}}, color = {0, 127, 255}));
  connect(pip3.port_b, pump1.port_a) annotation(
    Line(points = {{8, -78}, {25, -78}, {25, -70}, {42, -70}}, color = {0, 127, 255}));
  connect(pump1.port_b, pip4.port_a) annotation(
    Line(points = {{62, -70}, {106, -70}}, color = {0, 127, 255}));
  annotation(
    uses(Buildings(version = "9.1.0"), Modelica(version = "4.0.0")),
    Diagram(coordinateSystem(extent = {{-100, 200}, {160, -120}})),
    version = "");
end M510S_33_MBL;

Problem: When simulating the model (e.g., with start time 0 seconds, stop time 1000 seconds, and 500 number of intervals), I get the following error:

The following assertion has been violated at time 0.000000
pump1.etaHyd >= 0.0
Variable violating min constraint: 0.0 <= pump1.etaHyd, has value: -0.000687039

However, it seems that the simulation still finishes.

pump1.etaHyd is visualized in the following two diagrams.

Question: Unfortunately, I am not sure what causes pump1.etaHyd to be negative from 0-2 ms. I assume that I need to specify proper values for etaHydMet in the pump data model. However, I am not sure how I can find proper values for this parameter. I am aware of the Hydraulic efficiency section in the user guide (Buildings.Fluid.Movers.UsersGuide) and I tried to set etaHydMet to Buildings.Fluid.Movers.BaseClasses.Types.HydraulicEfficiencyMethod.NotProvided but this will then yield the following error:

The following assertion has been violated at time 0.000000
pump1.eff.yMot >= 0.0
Variable violating min constraint: 0.0 <= pump1.eff.yMot, has value: -2.29013e-07

How can I solve this issue?

Modelica Buildings Version: 10.0.0, 2022-12-06

Additionally, it is quite interesting that the simulation results diverge wildly from reality (i.e., the physical testbed). Although I am confident that I have parameterized the pump correctly, the liquid levels in both Tank 1 and Tank 2 are not increasing as rapidly as in real world. I suspect that the pressure parameters are misconfigured but I am not sure which ones have the main influence. Is there a strategy on how to debug this to converge to reality?

Answered by hcasperfu

Aug 18, 2023

Purely from a clarity point of view I believe it is better to set the pressure drop in the pipe components instead of in the pump component.
I am not familiar with the Standard Library components you are using and also cannot think of any model in Buildings library that does this on top of my head, so I cannot say what would be a good way to model the gravity effects. What could be potentially useful to you is the Buildings.Fluid.Movers.BaseClasses.IdealSource component. This model forces a flow or a pressure drop across it. I am thinking it could be used to prescribe a differential pressure caused by gravity effects, instead of modelling the gravity directly.
Another piece of advice woul…

View full answer

hcasperfu · 2023-08-04T23:06:38Z

hcasperfu
Aug 4, 2023
Collaborator

Greetings!

I am not able to run your code and I am a bit confused with which version of Buildings you are running it with.
In your code you have annotation(uses(Buildings(version = "9.1.0")), but you stated you were running it on 10.0.0. Furthermore, your code seems to contain variables/parameters both new (e.g. HydraulicEfficiencyMethod) and deprecated (e.g. speed_rpm_nominal).
I ran into errors with undeclared variables with either these versions loaded.
Can you please provide more details in this?

Cheers,
Casper

4 replies

MatthiasEckhart Aug 7, 2023
Author

Hi Casper,

thanks for helping and sorry for the confusion. Yes, I was using version 9.1.0 of the Modelica Buildings library. Unfortunately, I copied the version info from the user guide of the Modelica Buildings library, which is 10.0.0 in my case.

Interestingly, it appears to me that I did not run into errors with undeclared variables when using OpenModelica 1.19.0~dev-765-g5b322f1. However, when switching to OpenModelica 1.22.0~dev~256~g4ed5ffa-1.fc37, I received the following error:

[2] 10:04:47 Translation Error
[M510S_33_MBL: 29:35-29:73]: Class M510S_Data_4 does not satisfy the requirements for a package. Lookup is therefore restricted to encapsulated elements, but speed_rpm_nominal is not encapsulated.

I have fixed this by using an import statement in my model:

model M510S_33_MBL

import M510S_Data_4.*;

parameter Modelica.Units.SI.Density rho_default_this=Medium.density(state_default_this)
    "Density at nominal condition";
parameter Medium.ThermodynamicState state_default_this=
    Medium.setState_pTX(
      T=Medium.T_default,
      p=Medium.p_default,
      X=Medium.X_default[1:Medium.nXi]) "Default state";
      
parameter Modelica.Units.SI.Velocity v_nominal_this=0.15
    "Velocity at m_flow_nominal (used to compute default diameter)";
      
         parameter Modelica.Units.SI.MassFlowRate m_flow_nominal=2
    "Nominal mass flow rate for each fan";
  parameter Modelica.Units.SI.PressureDifference dp_nominal=500
    "Nominal pressure head for each fan";
      
package Medium = Buildings.Media.Water;
  Buildings.Fluid.Movers.SpeedControlled_y pump1(redeclare package Medium = Medium, redeclare replaceable
      M510S_Data_4 per,
      energyDynamics=Modelica.Fluid.Types.Dynamics.SteadyState,
      addPowerToMedium=false) annotation(
    Placement(visible = true, transformation(origin = {52, -70}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
   Modelica.Blocks.Sources.Constant rpm1(k= 10000) "Pump speed control signal"
    annotation (Placement(visible = true, transformation(extent = {{18, -26}, {30, -14}}, rotation = 0)));
  inner Modelica.Fluid.System system annotation(
    Placement(visible = true, transformation(origin = {100, 166}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
  Modelica.Blocks.Math.Gain gain1(k = 1 / speed_rpm_nominal) annotation(
    Placement(visible = true, transformation(origin = {87, -37}, extent = {{-7, -7}, {7, 7}}, rotation = 0)));
    Modelica.Fluid.Vessels.OpenTank tank1(redeclare package Medium = Medium, crossArea = 0.74832, height = 0.278, level_start = 0, nPorts = 2, portsData = {Modelica.Fluid.Vessels.BaseClasses.VesselPortsData(diameter = 0.006), Modelica.Fluid.Vessels.BaseClasses.VesselPortsData(diameter = 0.006)}, use_portsData = true)  annotation(
    Placement(visible = true, transformation(origin = {-52, 170}, extent = {{-20, -20}, {20, 20}}, rotation = 0)));
    Modelica.Fluid.Vessels.OpenTank tank2(redeclare package Medium = Medium, crossArea = 0.74832, height = 0.278, level_start = 0, nPorts = 2, portsData = {Modelica.Fluid.Vessels.BaseClasses.VesselPortsData(diameter = 0.006), Modelica.Fluid.Vessels.BaseClasses.VesselPortsData(diameter = 0.006)}, use_portsData = true)  annotation(
    Placement(visible = true, transformation(origin = {-66, 52}, extent = {{-20, -20}, {20, 20}}, rotation = 0)));
  Buildings.Fluid.Actuators.Valves.TwoWayLinear val1(redeclare package Medium = Medium,
    l=0.05,
    m_flow_nominal=2,
    use_inputFilter=false,
    dpValve_nominal=6000) annotation(
    Placement(visible = true, transformation(origin = {-64, 124}, extent = {{-10, -10}, {10, 10}}, rotation = -90)));
  Buildings.Fluid.Actuators.Valves.TwoWayLinear val2(redeclare package Medium = Medium,
    l=0.05,
    m_flow_nominal=2,
    use_inputFilter=false,
    dpValve_nominal=6000) annotation(
    Placement(visible = true, transformation(origin = {-68, 12}, extent = {{-10, -10}, {10, 10}}, rotation = -90)));
    Modelica.Blocks.Sources.Ramp y(
    
    duration= 0,height=1,
    offset=0) "Control signal"
                 annotation (Placement(visible = true, transformation(extent = {{16, 106}, {36, 126}}, rotation = 0)));
    Modelica.Fluid.Vessels.OpenTank basin1(redeclare package Medium = Medium, crossArea = 4.4156, height = 0.12, level_start = 0.05, nPorts = 2, portsData = {Modelica.Fluid.Vessels.BaseClasses.VesselPortsData(diameter = 0.006), Modelica.Fluid.Vessels.BaseClasses.VesselPortsData(diameter = 0.006)}, use_portsData = true) annotation(
    Placement(visible = true, transformation(origin = {-68, -58}, extent = {{-20, -20}, {20, 20}}, rotation = 0)));
  Buildings.Fluid.FixedResistances.Pipe pip1(redeclare package Medium = Medium, lambdaIns = 0, length = 0.12, m_flow_nominal = 0.006 ^ 2 * Modelica.Constants.pi * v_nominal_this * rho_default_this / 4, nSeg = 1, thicknessIns = 0.002) annotation(
    Placement(visible = true, transformation(origin = {-66, 96}, extent = {{-10, -10}, {10, 10}}, rotation = -90)));
  Buildings.Fluid.FixedResistances.Pipe pip4(redeclare package Medium = Medium, lambdaIns = 0, length = 2.68, m_flow_nominal = 0.006 ^ 2 * Modelica.Constants.pi * v_nominal_this * rho_default_this / 4, nSeg = 1, thicknessIns = 0.002) annotation(
    Placement(visible = true, transformation(origin = {116, -70}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
  Buildings.Fluid.FixedResistances.Pipe pip3(redeclare package Medium = Medium, lambdaIns = 0, length = 0.605, m_flow_nominal = 0.006 ^ 2 * Modelica.Constants.pi * v_nominal_this * rho_default_this / 4, nSeg = 1, thicknessIns = 0.002) annotation(
    Placement(visible = true, transformation(origin = {-2, -78}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
  Buildings.Fluid.FixedResistances.Pipe pip2(redeclare package Medium = Medium, lambdaIns = 0, length = 0.45, m_flow_nominal = 0.006 ^ 2 * Modelica.Constants.pi * v_nominal_this * rho_default_this / 4, nSeg = 1, thicknessIns = 0.002) annotation(
    Placement(visible = true, transformation(origin = {-68, -16}, extent = {{-10, -10}, {10, 10}}, rotation = -90)));

equation
  connect(rpm1.y, gain1.u) annotation(
    Line(points = {{31, -20}, {67.1, -20}, {67.1, -37}, {79, -37}}, color = {0, 0, 127}));
  connect(gain1.y, pump1.y) annotation(
    Line(points = {{95, -37}, {52, -37}, {52, -58}}, color = {0, 0, 127}));
  connect(y.y, val1.y) annotation(
    Line(points = {{37, 116}, {9.5, 116}, {9.5, 124}, {-52, 124}}, color = {0, 0, 127}));
  connect(val1.port_a, tank1.ports[1]) annotation(
    Line(points = {{-64, 134}, {-64, 142}, {-52, 142}, {-52, 150}}, color = {0, 127, 255}));
  connect(y.y, val2.y) annotation(
    Line(points = {{37, 116}, {-0.5, 116}, {-0.5, 72}, {0, 72}, {0, 13}, {-56, 13}, {-56, 12}}, color = {0, 0, 127}));
  connect(tank2.ports[1], val2.port_a) annotation(
    Line(points = {{-66, 32}, {-68, 32}, {-68, 22}}, color = {0, 127, 255}));
  connect(pip1.port_b, tank2.ports[2]) annotation(
    Line(points = {{-66, 86}, {-66, 32}}, color = {0, 127, 255}));
  connect(val1.port_b, pip1.port_a) annotation(
    Line(points = {{-64, 114}, {-66, 114}, {-66, 106}}, color = {0, 127, 255}));
  connect(pip4.port_b, tank1.ports[2]) annotation(
    Line(points = {{126, -70}, {150.5, -70}, {150.5, 150}, {-52, 150}}, color = {0, 127, 255}));
  connect(basin1.ports[1], pip3.port_a) annotation(
    Line(points = {{-68, -78}, {-12, -78}}, color = {0, 127, 255}));
  connect(pip2.port_b, basin1.ports[2]) annotation(
    Line(points = {{-68, -26}, {-68, -78}}, color = {0, 127, 255}));
  connect(val2.port_b, pip2.port_a) annotation(
    Line(points = {{-68, 2}, {-68, -6}}, color = {0, 127, 255}));
  connect(pip3.port_b, pump1.port_a) annotation(
    Line(points = {{8, -78}, {25, -78}, {25, -70}, {42, -70}}, color = {0, 127, 255}));
  connect(pump1.port_b, pip4.port_a) annotation(
    Line(points = {{62, -70}, {106, -70}}, color = {0, 127, 255}));
  annotation(
    uses(Buildings(version = "10.0.0"), Modelica(version = "4.0.0")),
    Diagram(coordinateSystem(extent = {{-100, 200}, {160, -120}})),
    version = "");
end M510S_33_MBL;

Note that I have now switched to version 10.0.0 of the Modelica Buildings library. Furthermore, I did not intend to use the deprecated parameter speed_rpm_nominal. I just defined this in my data model to specify the pump's nominal RPM instead of hard-coding it directly in my coupled-tanks model when calculating the gain (i.e., gain1).

For some reason the value of pump1.etaHyd of the constraint violation now changed to -0.000687039.

The following assertion has been violated at time 0.000000 ((pump1.etaHyd >= 0.0)) --> "Variable violating min constraint: 0.0 <= pump1.etaHyd, has value: -0.000687039"

However, the simulation still finishes successfully. Unfortunately, I am not sure how I can pinpoint the parameter that causes the constraint violation.

hcasperfu Aug 14, 2023
Collaborator

Thanks for the clarification and sorry for the late response. I am able to reproduce this warning message in OMC.
I think the negative efficiency came from the negative pressure at the start of the simulation, which produced negative work. However, some code was intentionally written in the fan model to prevent negative power. I am not sure how it slipped through in OMC. But all in all I don't think this is a huge problem.
I am more concerned about how the model failed to represent your test results. Can you provide more data/details in this? As a general guideline, the Euler number method is basically guesses and are only intended for the situation where you DON'T have data for the fan/pump. If you have data for your fan/pump, you should use Power_VolumeFlowRate or Efficiency_VolumeFlowRate.

Another suggestion is that, if you only need speed_rpm_nominal in the gain block, I would declare it at the top level together with v_nominal_this etc. To put simply, replace

import M510S_Data_4.*;

with

parameter Integer speed_rpm_nominal = 10000 "Nominal RPM";

This way you don't have to add a parameter declaration in a record class instantiated inside another instance, which can cause trouble. This helped me resolve some error messages when trying to run this code in Dymola. But Dymola still cannot instantiate this model.

MatthiasEckhart Aug 16, 2023
Author

Hi Casper,

thanks again for your ongoing support. I will ignore the constraint violation warning pertaining to pump1.etaHyd for now.

Thank you also for your suggestions on improving the declaration of speed_rpm_nominal.

Regarding the issue that the simulation results are not in line with the tests carried out with my physical testbed: I do believe that this is caused by an incorrect parameterization (and modeling on my side) rather than a bug in the Modelica Buildings Library. For example, when simulating the model for 1000 seconds, tank1.level increases to 26.5405 mm whereas in real-world I would reach a liquid level of 30 mm in maximum ~10 seconds. I believe that I need to tune the pressure value for the suction side of the pump (pump1.port_a.p) such that it represents my real-world measurements more accurately. However, I am not sure which parameters exactly need to be specified to achieve this behavior. Since both ports port_a and port_b are connected to Buildings.Fluid.FixedResistances.Pipe, do I need to set the pressure in the pipe components or the pump component?

Furthermore, somewhat related to the question on tuning the pressure variables: To model the flow behavior of gravity pulling water down from tank1 to tank2 and eventually basin1, do I need to set pressure values in pip1 and pip2 or do I have to model this in a different way?

hcasperfu Aug 18, 2023
Collaborator

Purely from a clarity point of view I believe it is better to set the pressure drop in the pipe components instead of in the pump component.
I am not familiar with the Standard Library components you are using and also cannot think of any model in Buildings library that does this on top of my head, so I cannot say what would be a good way to model the gravity effects. What could be potentially useful to you is the Buildings.Fluid.Movers.BaseClasses.IdealSource component. This model forces a flow or a pressure drop across it. I am thinking it could be used to prescribe a differential pressure caused by gravity effects, instead of modelling the gravity directly.
Another piece of advice would be using Buildings.Fluid.FixedResistances.PressureDrop instead of the pipe model. This model only cares about pressure drop, whilst the pipe model includes some other effects such as heat transfer but I don't see that you are using this. Opting for the simpler model can reduce the headache of parameterising them.

Answer selected by MatthiasEckhart

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Pump hydraulic efficiency constraint #3469

{{title}}

{{editor}}'s edit

{{editor}}'s edit

Replies: 1 comment 4 replies

{{title}}

{{title}}

{{title}}

{{title}}

{{title}}

Select a reply

Pump hydraulic efficiency constraint #3469

MatthiasEckhart Aug 4, 2023

Replies: 1 comment · 4 replies

hcasperfu Aug 4, 2023 Collaborator

MatthiasEckhart Aug 7, 2023 Author

hcasperfu Aug 14, 2023 Collaborator

MatthiasEckhart Aug 16, 2023 Author

hcasperfu Aug 18, 2023 Collaborator

MatthiasEckhart
Aug 4, 2023

Replies: 1 comment 4 replies

hcasperfu
Aug 4, 2023
Collaborator

MatthiasEckhart Aug 7, 2023
Author

hcasperfu Aug 14, 2023
Collaborator

MatthiasEckhart Aug 16, 2023
Author

hcasperfu Aug 18, 2023
Collaborator