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Glycol Cooling coil with Temperature below zero in E+. How to model?

asked 2018-12-08 03:11:03 -0500

Marco Giuliani's avatar

updated 2018-12-27 10:10:53 -0500

I have to model a Glicol Cooling system where the Glicol supply temperature is around -5°C. The IDF editor tells that the Water Coil works only for temperature above zero. There is a way to overcame this limitation?

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answered 2018-12-11 15:20:15 -0500

EnergyPlus supports glycol plant loops, and the water-side of Coil:Cooling:Water is able to handle temperatures below freeezing. But the chilled water coil model has no provisions for frost on the air side, so it's not valid below freezing. For cold-temperature applications, you need to use the refrigeration objects, starting with Refrigeration:AirChiller.

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Regarding the Coil:Cooling:Water I'd want to ask you some more details: If I follow with the model of glicol plant loop and water coil, the simulation will end with error, or I will get the results but they are wrong only because the energy use for defrosting are not accounted? Or the heat balance on the coil will be wrong with very unrealistic results due to the model formulation? In my case, the defrosting is done with water spraid on coil pack and I don't really care about the energy impact of this process since is meaningless in my application.

Your experience will be helpful

Marco Giuliani's avatar Marco Giuliani  ( 2018-12-13 10:09:23 -0500 )edit

A quick check of the coil source code does not reveal any error messages related to freezing temperatures, so it may work fine and simply remove moisture from the air like normal. Or you may run into some psychrometric function problems. The only way to know is to try it.

MJWitte's avatar MJWitte  ( 2018-12-14 13:29:11 -0500 )edit

And be sure to add output variables for all of the node conditions entering and leaving the coil so you can verify if energy is conserved and if the psychrometrics look reasonable.

MJWitte's avatar MJWitte  ( 2018-12-14 13:30:09 -0500 )edit

Dear @MJWitte, I have followed your advice and I delevop the model using the Refrigeration object. The documentation and other experiences on refrigeration system are quite limited and it is a challenge to setup something similar to real complex system.

Marco Giuliani's avatar Marco Giuliani  ( 2019-01-04 12:44:09 -0500 )edit

@MJWitte My approach is: Refrigeration:AirChiller+ZoneHVAC:RefrigerationChillerSet+Refrigeration:CaseAndWalkInList+Refrigeration:SecondarySystem+ Refrigeration:System+Refrigeration:Compressor+Refrigeration:WaterCooled+CondenserLoop+PlantComponent:TemperatureSource. The Simulation is running and the zone is cooled, but only AirChiller is working. The compressor never runs. I'm wondering if I understud well what AirChiller is, or if the setput is not correct.. It is a terminal unit or a Compact unit?

Marco Giuliani's avatar Marco Giuliani  ( 2019-01-04 12:48:23 -0500 )edit

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Asked: 2018-12-08 03:11:03 -0500

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Last updated: Dec 11 '18