Why has air terminal flow rate changed due to a version upgrade?

asked 2021-07-26 11:56:55 -0500

RCulham's avatar

updated 2021-07-26 12:02:59 -0500

I had created a project in OpenStudio 2-5-0 which uses the EnergyPlus 8.9 simulation engine. In this project, I was simulating a roof top single zone air-source heat pump with an energy recovery ventilator on the outdoor air system with a constant flow. I used uncontrolled diffusers as supply to the zones. I then loaded the version 2-5-0 *.osm file into OpenStudio 1-1-0 which uses the EnergyPlus 9.4 simulation engine. OpenStudio updated the *.osm file and replaced the uncontrolled terminals with constant volume terminals with no reheat. The change in the flow in reported for the diffusers is significant. The flows reported for version 2-5-0 are what to be expected, where as the flow reported in the newer version is much less in the order of 15 to 30 percent of the flow reported in the earlier version.

Why would this be? Is it a conversion error or the fact that EnergyPlus 9.4 no longer supports an uncontrolled diffuser?

Thankyouimage description

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