Issue3492 direct evaporative cooler by JayHuLBL · Pull Request #3755 · lbl-srg/modelica-buildings

JayHuLBL · 2024-03-29T20:49:13Z

This closes #3492.

Issue3492 direct evaporative cooler

…porative cooler calculations

…veCooler Issue3492 direct evaporative cooler

…m/lzwang26/modelica-buildings into issue3492_DirectEvaporativeCooler

Finalized the model clean up and documentation.

…veCooler Issue3492 direct evaporative cooler

JayHuLBL · 2025-08-20T21:54:57Z

@mwetter Would you please let us know if the new model Buildings.Fluid.Humidifiers.EvaporativeCoolers.Baseclasses.Xi_TDryBulTWetBul should be in the package Buildings.Utilities.Psychrometrics?

mwetter · 2025-08-20T22:15:20Z

@JayHuLBL : Thanks for checking. Yes the block should be moved. And its output Xi[] should actually be X_w similar than in Buildings.Utilities.Psychrometrics.X_pW because the implementation assigns only one element. Hence the block would be invalid if Medium.nXi > 1.

JayHuLBL · 2025-08-20T22:22:29Z

@JayHuLBL : Thanks for checking. Yes the block should be moved. And its output Xi[] should actually be X_w similar than in Buildings.Utilities.Psychrometrics.X_pW because the implementation assigns only one element. Hence the block would be invalid if Medium.nXi > 1.

Thanks! We will change it.

JayHuLBL · 2025-10-29T18:34:05Z

@karthikeyad-pnnl This PR looks good to me. Can you double-check if everything looks good to you? Otherwise, we can ask Michael to review.

karthikeyad-pnnl · 2025-10-29T20:03:56Z

@JayHuLBL Thank you! I will get back to you shortly after review

JayHuLBL · 2025-11-04T21:47:54Z

@karthikeyad-pnnl Is it ready for Michael's review?

…ler' into issue3492_DirectEvaporativeCooler

…ativeCooler Issue3492 direct evaporative cooler

JayHuLBL · 2026-03-10T17:05:27Z

@mwetter It's ready for review.

mwetter

I don't see how to realistically use these components as the evaporative cooling is always operating. I expect users use these components as part of an air handler unit, in which case the evaporative cooling would not be operating if the system is in heating mode. Therefore, we need to add control input that allows modulating the humidification.

Moreover, the comment about advanced users being able to change the components of the Direct model does not make sense. It also makes me wonder if this is a generic component or whether it is for a particular product, yet it exposes the depth and area, which makes me think it can be changed. However, it is not clear if changing them invalidates the default coefficients, which are not defined and are protected.

Also, the consumed water must be an output to allow assessing water use.

So, this PR is far from being finished and need more work and substantial better review.

mwetter · 2026-03-23T23:42:42Z

This component requires a control input to modulate the evaporative cooling.

mwetter · 2026-03-23T23:42:55Z

This component requires a control input to modulate the evaporative cooling.

mwetter · 2026-03-23T23:43:03Z

This component requires a control input to modulate the evaporative cooling.

mwetter · 2026-03-23T23:44:01Z

+within Buildings.Fluid.Humidifiers.EvaporativeCoolers;
+model IndirectDry
+  "Indirect dry evaporative cooler"
+  extends Buildings.Fluid.Interfaces.PartialFourPortParallel;


All other components in the library extend from PartialFourPort. Use this also here, otherwise we have one component for which the user need for no obvious reason connect the fluid ports differently.

mwetter · 2026-03-23T23:44:11Z

@@ -0,0 +1,246 @@
+within Buildings.Fluid.Humidifiers.EvaporativeCoolers;
+model IndirectWet "Indirect wet evaporative cooler"
+  extends Buildings.Fluid.Interfaces.PartialFourPortParallel;


All other components in the library extend from PartialFourPort. Use this also here, otherwise we have one component for which the user need for no obvious reason connect the fluid ports differently.

mwetter · 2026-03-23T23:55:38Z

+    "Coefficients for evaporative medium efficiency calculation";
+
+equation
+  vel =abs(V_flow)/padAre;


We use regularization for this to make the function $C^1$.

mwetter · 2026-03-23T23:56:02Z

+    "Actual efficiency of component";
+
+equation
+  eff = max((maxEff - floRat*abs(VPri_flow)/abs(VSec_flow)),0);


We use regularization for this to make the function $C^1$.

mwetter · 2026-03-24T00:06:05Z

+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>


What???
Not even a "advanced user" can modify this as it is protected and the language does not allow changing protected assignment. And this is for a specific pad. This makes me wonder if this is a generic model that can be parameterized for a specific equipment, or whether it just happened to be for one specific equipment, in which case exposing dep and padAre would not make sense.

You need to finish the implementation and documenation.

The coefficient need to be explained. How are they defined? Add it to the documentation of the model, including the top-level model. Are they invariant if dep or padAre are changed?

Propagate the device specific parameters dep, padAre and coe into a data record, to be put into EvaporativeCoolers.Data

mwetter · 2026-03-24T00:09:03Z

+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>) +


Use proper notation:

no need to put the dep and vel into brackets, these are just factors.

Either use parameter names and Courier font, or use mathematical symbols and italics font.

This would be much more readable as a sum notation.

Also, explain where the user can get these data.

mwetter · 2026-03-24T00:10:21Z

+  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);


This implementation is very expensive, computing the 2nd and 3rd power of vel and dep multiple times. Do it efficiently.

karthikeyad-pnnl · 2026-03-24T18:45:34Z

I don't see how to realistically use these components as the evaporative cooling is always operating. I expect users use these components as part of an air handler unit, in which case the evaporative cooling would not be operating if the system is in heating mode. Therefore, we need to add control input that allows modulating the humidification.

Moreover, the comment about advanced users being able to change the components of the Direct model does not make sense. It also makes me wonder if this is a generic component or whether it is for a particular product, yet it exposes the depth and area, which makes me think it can be changed. However, it is not clear if changing them invalidates the default coefficients, which are not defined and are protected.

Also, the consumed water must be an output to allow assessing water use.

So, this PR is far from being finished and need more work and substantial better review.

@mwetter Thank you for the feedback. I am adding some additional contextual information and a list of improvements I will make.

The original intended use of this model was as zonal cooling equipment that cycles when the zone temperature exceeds the cooling setpoint. In addition to updating the documentation, I think it may make more sense to add a typical use-case in a zonal unit within the Buildings.Fluid.ZoneEquipment package.
I will also search for any specialized equipment that manage the cooling output for use in air-handlers, in which case it may make sense to incorporate the variable cooling output feature into the model. If I dont find any, I will still add an example of how the component can be integrated into an AHU to achieve supply temperature setpoint (variable cooling).
Based on the EnergyPlus documentation, the performance coefficients represent a commonly used evaporative media called a CelDek pad, which can be procured in multiple sizes. I will look for any performance coefficients that might be available for other media, and update the code to propagate the parameters from a data record.

List of actions

Add model for use in zonal unit and a suitable example for the zonal unit.
Identify any special equipment for use in air handling units. If none are found, add example of how the component can be used to achieve supply temperature setpoint (variable cooling).
Propagate the performance coefficients through data records.
Update the models with secondary vented air-stream to incorporate correct changes in mixed-air states for the secondary stream.
Address all other comments.

mwetter · 2026-03-25T13:59:26Z

@karthikeyad-pnnl : For the adiabatic cooler, besides use in air handler units, which was used quite a bit in Europe's dry climate, another important use case is to precondition the outside air in cooling towers such as in https://peakplus.energy/

karthikeyad-pnnl and others added 30 commits August 30, 2023 16:45

Added direct evaporative cooler blocks to Buildings library

2286744

Merge branch 'lbl-srg:master' into issue3492_DirectEvaporativeCooler

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Change path for missing blocks.

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Change istance names of the models.

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Add comments for variables and parameters in model 'DirectCalculations'

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Clean block 'DirectCalculations' according to the conventions.

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Clean the model 'Direct'

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Add documentations and icons

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Add documentations.

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Merge pull request #85 from lzwang26/issue3492_DirectEvaporativeCooler

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Issue3492 direct evaporative cooler

Added validation scripts and modified validation model for direct eva…

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…porative cooler calculations

Updated resources and scripts for validation models

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Merge pull request #1 from karthikeyad-pnnl/issue3492_DirectEvaporati…

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…veCooler Issue3492 direct evaporative cooler

Further clean up the model 'Xi_TDryBulTWetBul'

a9346c9

Further clean up the model 'DirectCalculations'

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Further clean up the model 'Direct'

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Clean up the model 'Validation.DirectCalculations'

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Clean up the model 'Validation.DirectCalculations'

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Clean up the model 'Validation.Direct'

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Add documentation for the direct calculation validation.

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Finalized the documentations for all the models.

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Merge branch 'issue3492_DirectEvaporativeCooler' of https://github.co…

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…m/lzwang26/modelica-buildings into issue3492_DirectEvaporativeCooler

Correct the path of DirectCalculations.mos

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Add the script file.

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Merge pull request #87 from lzwang26/issue3492_DirectEvaporativeCooler

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Finalized the model clean up and documentation.

Added files for indirect dry evaporative cooler

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Updated models and added validation script and reference data

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Merge pull request #2 from karthikeyad-pnnl/issue3492_DirectEvaporati…

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…veCooler Issue3492 direct evaporative cooler

Revise the documentation of 'Baseclasses.Validation.DirectCalculations'

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Revise the documentation of 'Validation.Direct'

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updated release note

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mwetter assigned JayHuLBL Aug 20, 2025

JayHuLBL added 3 commits August 20, 2025 11:30

merged maaster

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removed not used input

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created validation for the water vapor fraction calculation

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JayHuLBL added 4 commits August 20, 2025 15:54

changed the Xi[] to X_w, moved to psychrometrics package

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improved graphics

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resolved conflict

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improved graphics

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karthikeyad-pnnl added 2 commits November 13, 2025 17:24

Updated documentation for all validation models and one component model

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Merge remote-tracking branch 'upstream/issue3492_DirectEvaporativeCoo…

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…ler' into issue3492_DirectEvaporativeCooler

karthikeyad-pnnl mentioned this pull request Nov 14, 2025

Issue3492 direct evaporative cooler #4405

Merged

JayHuLBL and others added 5 commits November 14, 2025 09:00

Merge pull request #4405 from karthikeyad-pnnl/issue3492_DirectEvapor…

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…ativeCooler Issue3492 direct evaporative cooler

updated openmodelica script

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Merge branch 'master' into issue3492_DirectEvaporativeCooler

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Merge branch 'master' into issue3492_DirectEvaporativeCooler

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merged master

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mwetter added 3 commits March 23, 2026 16:14

Added attributes

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Updated capitalization

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Initial small review

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mwetter requested changes Mar 24, 2026

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