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Why Don't I Need a DX Cooling Coil Plant-Side

asked 2018-10-02 12:50:12 -0600

jbatt gravatar image

updated 2018-10-03 15:05:03 -0600

I currently have a DX Cooling Coil providing cooling in my supply air, but I haven't got any sort of cooling plant in my model. If the element is truly just a cooling coil, wouldn't that mean that this is just the evaporator? How can cooling possibly be occurring?

What I was hoping was to have the condenser associated with this evaporator reject heat to a cooling tower. Is the element in OpenStudio a complete DX system (evaporator and condenser) with the assumption being that it is air-cooled?

Thanks!image description

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FYI - this image you added of the Refrigeration Condenser Water Cooled item from OpenStudio's HVAC library is meant to be used exclusively for refrigeration systems (walk-in or cases in grocery stores, for example). They can't be used in an air or plant system like you want.

Aaron Boranian gravatar image Aaron Boranian  ( 2018-10-03 18:13:57 -0600 )edit

@Aaron Boranian Thanks for the heads up...I was a little suspicious of that.

jbatt gravatar image jbatt  ( 2018-10-04 05:51:51 -0600 )edit

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answered 2018-10-03 12:22:45 -0600

If you want to cool using a plant loop, then choose a CoolingCoil:Water instead of a CoolingCoilDX object. Then create a water loop with an air or water cooled chiller, depending on your use case. Water cooled if you will have a cooing tower.

On the HVAC tab of the OpenStudio application if you click the green plus at the top left you will open a dialog to make various HVAC systems. If you choose "Packaged Rooftop VAV with Reheat" you can inspect the resulting system that has an air loop serving the zones, a chiller water loop, and a condenser water loop.

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Thanks, David. That sounds like a reasonable strategy...the only hesitation that I had about doing just that was that in the building I am modeling this is an evaporator coil and I was afraid CoolingCoil:Water would behave as a CHW coil - without any phase change occurring. Is this not something that I need to worry about?

The plant-side that you described is exactly what I'm looking for.

jbatt gravatar image jbatt  ( 2018-10-03 12:31:46 -0600 )edit
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I believe what the user is asking for is a water-cooled DX cooling coil. So only the condenser water loop would be necessary. Does OS have water-cooled DX coils?

rraustad gravatar image rraustad  ( 2018-10-03 12:39:38 -0600 )edit

That's correct. Or some kind of work around using an ordinary cooling coil as David suggested and equating the performance to that of a water-cooled DX coil

jbatt gravatar image jbatt  ( 2018-10-03 12:44:11 -0600 )edit

This answer might be useful.

Eric Ringold gravatar image Eric Ringold  ( 2018-10-03 13:42:51 -0600 )edit

Ideally, though, it would be a refrigerant (not water) exchanging heat with my air-stream and water loop

jbatt gravatar image jbatt  ( 2018-10-03 15:00:52 -0600 )edit

The hope was that I could either connect my DX coil to the object in the above image or that there was an evaporator side that corresponded to this object (I can't seem to find one).

jbatt gravatar image jbatt  ( 2018-10-03 15:04:27 -0600 )edit

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Asked: 2018-10-02 12:50:12 -0600

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Last updated: Oct 03 '18