Unmethours decreased by increasing the temperature of cold air.

asked 2020-09-29 16:25:06 -0600

Rwadhwa910's avatar

updated 2020-10-01 09:50:19 -0600

I am running a college building model that consists of Classroom, Cafe , Office and Atrium. While simulating the OS model, there were close to 2000 unmethours reported by the model, I tried to reduce the unmethours by lowering the temperature from 55 to 50 Fof zone cooling design supply air, which could result in increase of energy transfer by the cold air, but I found out that cooling energy decreased when decreasing the temperature which is quite different than what i anticipated, so i tried to increase the temperature for the supply cold air to 60 F and surprisingly the cooling coil energy increased and the no of unmethours in the model decreased to two digits , the unmet hours were only present in the Cafe, Atrium and Office zones only. Could somebody tell me why increasing the temperature may result in increase in cooling energy?

Also I am using a District system and that is set to autosize which means that the system will supply the energy as desired by the zone, but while inspecting the time series data I found that the unmethours were because the system was not able to supply the desired amount of cooling energy resulting in increase in the temperature.

What can I do in my model reduce the unmethours apart from increasing the supply air temperature?

I have attached the model and the screenshot of the cooling energy transferred by the coil at 50, 55, and 60 F temperature.


image description

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