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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

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

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

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Last updated: Oct 03 '18