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How to Model Water-Side Economizer in OpenStudio

asked 2015-06-29 15:27:04 -0500

Brian C's avatar

updated 2015-06-29 16:10:20 -0500

I would like to know how others have modeled a water-side (hydronic) economizer using OpenStudio. To achieve the best controls with this solution, which method have you taken?

Specifically I am looking to model a cooling tower which will provide either chilled water directly to the AHUs via a fluid-to-fluid heat-exchanger and/or condenser water to the water-cooled chiller when the chiller is enabled to meet demand. Ideally there would be a modulating valve to allow for part-load economizing and would be the same coil in the AHUs.

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answered 2015-06-29 16:24:47 -0500

You can do a water side economizer quite easily on OS with the "HeatExchanger:FluidToFluid" object.

Add this object onto your chilled water loop on the supply equipment inlet node. This way E+ will try to use this object before your chiller to cool.

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Next, add this HX to your condenser loop on the demand side. To do this you MUST grab this object from the my model tab on the left, otherwise you will just create two HX that are not connected. Check by clicking on the dots above or below the HX to check it is linked up how you want it to be.

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This looks like an integrated WSE. How would you model the performance of a non-integrated WSE?

Lincoln's avatar Lincoln  ( 2015-06-29 18:22:08 -0500 )edit

Per E+ example files, for non-integrated WSE, instead of putting HeatExchanger:FluidToFluid in series with the Pump in the first step, the HX should be placed in parallel branch of chiller in the chilled water loop. All other steps may be same as described above. Though have never tried it myself in OS.

Chandan Sharma's avatar Chandan Sharma  ( 2015-06-30 01:48:15 -0500 )edit

@TaylorRoberts, thanks this was a very helpful guide to creating the integrated WSE I was looking to model. I did have to add another set-point manager after my fluid-to-fluid hx in my CHW loop in order for the model to run. Not sure if that was necessary or if I needed it for another reason but thought I would add that.

Brian C's avatar Brian C  ( 2015-06-30 11:00:10 -0500 )edit

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Asked: 2015-06-29 15:27:04 -0500

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Last updated: Jun 29 '15