Issue3492 direct evaporative cooler #3755
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| within Buildings.Fluid.Humidifiers.EvaporativeCoolers.Baseclasses; | ||
| block Direct | ||
| "Calculates the water vapor mass flow rate of a direct evaporative cooler" | ||
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| replaceable package Medium = Modelica.Media.Interfaces.PartialMedium | ||
| "Medium"; | ||
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| parameter Modelica.Units.SI.Area padAre | ||
| "Area of the rigid media evaporative pad"; | ||
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| parameter Modelica.Units.SI.Length dep | ||
| "Depth of the rigid media evaporative pad"; | ||
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| Real eff( | ||
| final unit="1") | ||
| "Evaporative humidifier efficiency"; | ||
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| Buildings.Controls.OBC.CDL.Interfaces.RealInput V_flow( | ||
| final unit="m3/s", | ||
| final quantity = "VolumeFlowRate") | ||
| "Air volume flow rate" | ||
| annotation (Placement(transformation(origin={-120,-20},extent={{-20,-20},{20,20}}), | ||
| iconTransformation(origin={-120,-20}, extent={{-20,-20},{20,20}}))); | ||
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| Buildings.Controls.OBC.CDL.Interfaces.RealInput TDryBulIn( | ||
| final unit="K", | ||
| displayUnit="degC", | ||
| final quantity="ThermodynamicTemperature") | ||
| "Dry bulb temperature of the inlet air" | ||
| annotation (Placement(transformation(origin={-120,60},extent={{-20,-20},{20,20}}), | ||
| iconTransformation(origin={-120,20}, extent={{-20,-20},{20,20}}))); | ||
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| Buildings.Controls.OBC.CDL.Interfaces.RealInput TWetBulIn( | ||
| final unit="K", | ||
| displayUnit="degC", | ||
| final quantity="ThermodynamicTemperature") | ||
| "Wet bulb temperature of the inlet air" | ||
| annotation (Placement(transformation(origin={-120,20}, extent={{-20,-20},{20,20}}), | ||
| iconTransformation(origin={-120,60}, extent={{-20,-20},{20,20}}))); | ||
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| Buildings.Controls.OBC.CDL.Interfaces.RealInput p( | ||
| final unit="Pa", | ||
| final quantity="Pressure") | ||
| "Inlet air pressure" | ||
| annotation (Placement(transformation(origin={-120,-60},extent={{-20,-20},{20,20}}), | ||
| iconTransformation(origin={-120,-60}, extent={{-20,-20},{20,20}}))); | ||
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| Buildings.Controls.OBC.CDL.Interfaces.RealOutput dmWat_flow( | ||
| final unit="kg/s", | ||
| final quantity="MassFlowRate") | ||
| "Water vapor mass flow rate difference between inlet and outlet" | ||
| annotation (Placement(transformation(origin={120,0}, extent={{-20,-20},{20,20}}), | ||
| iconTransformation(origin={120,0}, extent={{-20,-20},{20,20}}))); | ||
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| Buildings.Utilities.Psychrometrics.Xw_TDryBulTWetBul XWOut( | ||
| redeclare package Medium = Medium) | ||
| "Water vapor mass fraction at the outlet"; | ||
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| Buildings.Utilities.Psychrometrics.Xw_TDryBulTWetBul XWIn( | ||
| redeclare package Medium = Medium) | ||
| "Water vapor mass fraction at the inlet"; | ||
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| Modelica.Units.SI.Velocity vel | ||
| "Air velocity"; | ||
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| Modelica.Units.SI.ThermodynamicTemperature TDryBulOut( | ||
| displayUnit="degC") | ||
| "Dry bulb temperature of the outlet air"; | ||
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| protected | ||
| parameter Medium.ThermodynamicState sta_default=Medium.setState_pTX( | ||
| T=Medium.T_default, | ||
| p=Medium.p_default, | ||
| X=Medium.X_default) | ||
| "Default state of medium"; | ||
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| parameter Modelica.Units.SI.Density rho_default=Medium.density(sta_default) | ||
| "Density, used to compute fluid volume"; | ||
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| parameter Real effCoe[11] = {0.792714, 0.958569, -0.25193, -1.03215, 0.0262659, | ||
| 0.914869, -1.48241, -0.018992, 1.13137, 0.0327622, | ||
| -0.145384} | ||
| "Coefficients for evaporative medium efficiency calculation"; | ||
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| equation | ||
| vel =abs(V_flow)/padAre; | ||
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Member
There was a problem hiding this comment. We use regularization for this to make the function |
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| eff = effCoe[1] + effCoe[2]*(dep) + effCoe[3]*(vel) + effCoe[4]*(dep^2) + | ||
| effCoe[5]*(vel^2) + effCoe[6]*(dep*vel) + effCoe[7]*(vel*dep^2) + | ||
| effCoe[8]*(dep*vel^3) + effCoe[9]*(dep^3*vel) + effCoe[10]*(vel^3*dep^2) + | ||
| effCoe[11]*(dep^3*vel^2); | ||
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Member
There was a problem hiding this comment. This implementation is very expensive, computing the 2nd and 3rd power of |
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| TDryBulOut = TDryBulIn - eff*(TDryBulIn - TWetBulIn); | ||
| TDryBulIn = XWIn.TDryBul; | ||
| TWetBulIn = XWIn.TWetBul; | ||
| p = XWIn.p; | ||
| TWetBulIn = XWOut.TWetBul; | ||
| p = XWOut.p; | ||
| TDryBulOut = XWOut.TDryBul; | ||
| dmWat_flow = (XWOut.X_w - XWIn.X_w)*V_flow*rho_default; | ||
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| annotation (Documentation(info="<html> | ||
| <p> | ||
| Block that calculates the water vapor mass flow rate addition in the | ||
| direct evaporative cooler component. The calculations are based on the direct | ||
| evaporative cooler model in the Engineering Reference document from EnergyPlus v23.1.0. | ||
| </p> | ||
| <p> | ||
| The effectiveness of the evaporative media <code>eff</code> is calculated using | ||
| the curve | ||
| </p> | ||
| <p align=\"center\" style=\"font-style:italic;\"> | ||
| eff = effCoe[1] + effCoe[2]*(dep) + effCoe[3]*(vel) + effCoe[4]*(dep<sup>2</sup>) + | ||
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Member
There was a problem hiding this comment. Use proper notation:
Also, explain where the user can get these data. |
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| effCoe[5]*(vel<sup>2</sup>) + effCoe[6]*(dep*vel) + effCoe[7]*(vel*dep<sup>2</sup>) + | ||
| effCoe[8]*(dep*vel<sup>3</sup>) + effCoe[9]*(dep<sup>3</sup>*vel) + effCoe[10]*(vel<sup>3</sup>*dep<sup>2</sup>) + | ||
| effCoe[11]*(dep<sup>3</sup>*vel<sup>2</sup>) | ||
| </p> | ||
| <p> | ||
| where <code>effCoe[:]</code> is the evaporative efficiency coefficients for the | ||
| CelDek rigid media pad used in evaporative coolers. It is currently protected from | ||
| modification by the user, but can be modified for other materials within this class | ||
| by advanced users. <code>dep</code> is the depth of the evaporative media, and | ||
| <code>vel</code> is the velocity of the fluid media which is calculated from the volume flowrate | ||
| <code>V_flow</code> and evaporative media cross-sectional area <code>padAre</code> | ||
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Member
There was a problem hiding this comment. What??? You need to finish the implementation and documenation.
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| using | ||
| </p> | ||
| <p align=\"center\" style=\"font-style:italic;\"> | ||
| vel = V_flow/padAre | ||
| </p> | ||
| <p> | ||
| The outlet air drybulb temperature <code>TDryBulOut</code> is calculated using | ||
| the heat-balance equation | ||
| </p> | ||
| <p align=\"center\" style=\"font-style:italic;\"> | ||
| TDryBulOut = TDryBulIn - eff*(TDryBulIn - TWetBulIn) | ||
| </p> | ||
| <p> | ||
| where <code>TDryBulIn</code> is the inlet air drybulb temperature and | ||
| <code>TWetBulIn</code> is the inlet air wetbulb temperature. | ||
| </p> | ||
| <p> | ||
| The humidity ratio difference between the inlet and outlet air is used to | ||
| calculate the added mass of water vapor <code>dmWat_flow</code>, with the humidity | ||
| ratios being determined from psychrometric relationships, while assuming the | ||
| outlet air wetbulb temperature is the same as inlet air wetbulb temperature. | ||
| </p> | ||
| </html>", revisions="<html> | ||
| <ul> | ||
| <li> | ||
| September 14, 2023 by Cerrina Mouchref, Karthikeya Devaprasad, Lingzhe Wang:<br/> | ||
| First implementation. | ||
| </li> | ||
| </ul> | ||
| </html>"), Icon(graphics={ | ||
| Text(extent={{-152,144},{148,104}}, textString="%name", textColor={0,0,255}), | ||
| Rectangle(extent={{-100,100},{100,-100}}, lineColor={0,0,0}, | ||
| fillColor={255,255,255}, fillPattern=FillPattern.Solid)})); | ||
| end Direct; | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,117 @@ | ||
| within Buildings.Fluid.Humidifiers.EvaporativeCoolers.Baseclasses; | ||
| block IndirectWet | ||
| "Calculates the heat transfer in an indirect wet evaporative cooler" | ||
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| parameter Real maxEff( | ||
| final unit="1") | ||
| "Maximum efficiency of heat exchanger coil"; | ||
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| parameter Real floRat( | ||
| final unit="1") | ||
| "Coil flow efficency ratio of actual to maximum heat transfer rate"; | ||
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| Buildings.Controls.OBC.CDL.Interfaces.RealInput VPri_flow( | ||
| final unit="m3/s", | ||
| final quantity = "VolumeFlowRate") | ||
| "Primary air volume flow rate" | ||
| annotation (Placement(transformation(origin={-120,-60}, extent={{-20,-20},{20,20}}), | ||
| iconTransformation(origin={-140,-60}, extent={{-20,-20},{20,20}}))); | ||
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| Buildings.Controls.OBC.CDL.Interfaces.RealInput VSec_flow( | ||
| final unit="m3/s", | ||
| final quantity = "VolumeFlowRate") | ||
| "Secondary air volume flow rate" | ||
| annotation (Placement(transformation(origin={-120,-100}, extent={{-20,-20},{20,20}}), | ||
| iconTransformation(origin={-140,-100}, extent={{-20,-20},{20,20}}))); | ||
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| Buildings.Controls.OBC.CDL.Interfaces.RealInput TDryBulPriIn( | ||
| final unit="K", | ||
| displayUnit="degC", | ||
| final quantity="ThermodynamicTemperature") | ||
| "Dry bulb temperature of the primary inlet air" | ||
| annotation (Placement(transformation(origin={-120,100}, extent={{-20,-20},{20,20}}), | ||
| iconTransformation(origin={-140,100}, extent={{-20,-20},{20,20}}))); | ||
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| Buildings.Controls.OBC.CDL.Interfaces.RealInput TDryBulSecIn( | ||
| final unit="K", | ||
| displayUnit="degC", | ||
| final quantity="ThermodynamicTemperature") | ||
| "Dry bulb temperature of the secondary inlet air" | ||
| annotation (Placement(transformation(origin={-120,20}, extent={{-20,-20},{20,20}}), | ||
| iconTransformation(origin={-140,20}, extent={{-20,-20},{20,20}}))); | ||
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| Buildings.Controls.OBC.CDL.Interfaces.RealInput TWetBulSecIn( | ||
| final unit="K", | ||
| displayUnit="degC", | ||
| final quantity="ThermodynamicTemperature") | ||
| "Wet bulb temperature of the secondary inlet air" | ||
| annotation (Placement(transformation(origin={-120,-20}, extent={{-20,-20},{20,20}}), | ||
| iconTransformation(origin={-140,-20}, extent={{-20,-20},{20,20}}))); | ||
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| Buildings.Controls.OBC.CDL.Interfaces.RealOutput TDryBulPriOut( | ||
| displayUnit="degC", | ||
| final unit="K", | ||
| final quantity="ThermodynamicTemperature") | ||
| "Dry bulb temperature of the outlet air" | ||
| annotation (Placement(transformation(origin={120,0}, extent={{-20,-20},{20,20}}), | ||
| iconTransformation(origin={140,0}, extent={{-20,-20},{20,20}}))); | ||
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| Real eff( | ||
| unit="1") | ||
| "Actual efficiency of component"; | ||
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| equation | ||
| eff = max((maxEff - floRat*abs(VPri_flow)/abs(VSec_flow)),0); | ||
|
Member
There was a problem hiding this comment. We use regularization for this to make the function |
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| TDryBulPriOut = TDryBulPriIn - eff*(TDryBulSecIn - TWetBulSecIn); | ||
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| annotation (defaultComponentName="indWetCal", | ||
| Documentation(info="<html> | ||
| <p> | ||
| Block that calculates the water vapor mass flow rate addition in the | ||
| indirect evaporative cooler component. The calculations are based on the indirect | ||
| wet evaporative cooler model in the Engineering Reference document from EnergyPlus | ||
| v23.1.0. | ||
| </p> | ||
| <p> | ||
| The effective efficiency of the heat exchanger <code>eff</code> is calculated using | ||
| the formula | ||
| </p> | ||
| <p align=\"center\" style=\"font-style:italic;\"> | ||
| eff = max((maxEff - floRat*abs(VPri_flow)/abs(VSec_flow)), 0) | ||
| </p> | ||
| <p> | ||
| where <code>VPri_flow</code> and <code>VSec_flow</code> are the volume flow | ||
| rates of the primary and secondary fluid media respectively. The maximum | ||
| efficiency of the heat exchanger <code>maxEff</code> and the efficiency-reduction | ||
| coil flow ratio <code>floRat</code> are empirically determined for the specific | ||
| equipment based on experiments. | ||
| </p> | ||
| <p> | ||
| The outlet primary fluid drybulb temperature <code>TDryBulPriOut</code> is calculated | ||
| using the energy-balance equation | ||
| </p> | ||
| <p align=\"center\" style=\"font-style:italic;\"> | ||
| TDryBulPriOut = TDryBulPriIn - eff*(TDryBulSecIn - TWetBulSecIn) | ||
| </p> | ||
| <p> | ||
| where <code>TDryBulPriIn</code> is the inlet primary fluid drybulb temperature, | ||
| <code>TDryBulSecIn</code> is the inlet secondary fluid drybulb temperature and | ||
| <code>TWetBulSecIn</code> is the inlet secondary fluid wetbulb temperature. | ||
| </p> | ||
| </html>", revisions="<html> | ||
| <ul> | ||
| <li> | ||
| September 29, 2023 by Karthikeya Devaprasad:<br/> | ||
| First implementation. | ||
| </li> | ||
| </ul> | ||
| </html>"), Icon(coordinateSystem(extent={{-120,-120},{120,120}}), | ||
| graphics={Text( | ||
| extent={{-150,160},{150,120}}, | ||
| textString="%name", | ||
| textColor={0,0,255}), Rectangle(extent={{-120,120},{120,-120}}, | ||
| lineColor={0,0,0}, | ||
| fillColor={255,255,255}, | ||
| fillPattern=FillPattern.Solid)}), | ||
| Diagram(coordinateSystem(extent={{-100,-120},{100,120}}))); | ||
| end IndirectWet; | ||
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Change to using
m_flowas input. This implementation is very convoluted:First, in the sensor, density must be calculated to convert mass to volume flow rate. Then, here density must be computed to convert it back to mass flow rate. Moreover, the media must be propagated just to access the density function, which in fact uses default temperature and species, differently from the density computed in the volume flow meter.