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Cooling tower out of model boundaries E+

asked 2019-07-02 08:12:01 -0500

Saif gravatar image

updated 2019-07-17 07:45:35 -0500

I am using OpenStudio / EnergyPlus to model a residential building that utilize water source heat pumps with cooling tower and boiler, after running the simulation I received warnings related to range temperature and approach temperature being out of the model boundaries and suggesting that it will not impact the cooling tower performance. Since I am not an expert in EnergyPlus I wanted to check the effect of this warning so I plotted the inlet and outlet temperature for the supply side of the loop, I noticed that the inlet and outlet temperatures increase and fluctuate when the outside air wet bulb temperature reaches 66 F as you can see in the first and second screen shot. I am guessing this will impact the energy consumption because the WSHP performance decreases when the loop temperature increases, any Idea how to solve this?

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Edit: add picture for different types of cooling towers

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answered 2019-07-11 14:42:17 -0500

Based on the first warning about approach temperature and a search of the source code it appears that this CoolingTower:VariableSpeed specified the "CoolToolsCrossFlow" model type which sets the range for approach at 1.11 - 11.11 C.

Without the full idf to see what else is happening, I would suggest switching to the "YorkCalc" model which sets the approach range to 1.11 - 40.0 C. If that doesn't control well, I would try one of the other cooling tower types, either CoolingTower:SingleSpeed or CoolingTower:TwoSpeed.

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Thank you Michael for the response. I tried using “YorkCalc” but it gave similar results to “CoolToolsCrossFlow” model however using the SinglesSpeed cooling tower as you suggested above showed a really good control over the supply temperature as you can seen in the screen shot I added to the question, but the system design is a variable speed cooling tower, the link for the idf file is here

Saif gravatar imageSaif ( 2019-07-17 07:49:42 -0500 )edit
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I'm stumped. Even doubling the tower size doesn't improve the outlet temperature control. New issue posted. #7464

MJWitte gravatar imageMJWitte ( 2019-08-20 12:00:29 -0500 )edit

Thanks for following up.

Saif gravatar imageSaif ( 2019-08-21 07:47:32 -0500 )edit

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Asked: 2019-07-02 08:12:01 -0500

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Last updated: Jul 17