How problematic is modeling displacement ventilation with EnergyPlus?

asked 2019-03-13 14:44:02 -0500

Oleks gravatar image

updated 2019-03-13 17:00:03 -0500

Hi All,

I am modeling DOE Prototype Medium Office in Phoenix, AZ with Displacement Ventilation (DV), Air-to-air Heat Exchanger, Economizer, LowTemperatureRadiant:Electric for zone heating, and one AHU per floor. For displacement ventilation, I have One Node Displacement Ventilation models for the perimeter zones and Three Node Displacement Ventilation models for the core zones since the E+ documentation states that the latter ones should not be used for zones with high external loads. I have set up (or I hope I did with Heating Design Air Flow Method set as Flow/Zone and the values set to minimum OA requirements) the controls so that there is only the minimum outdoor air flow rate supplied to the zones during heating since max SAT is 68 F and heating setpoint is 69.8 F, and all the heating is provided by the LowTemperatureRadiant:Electric. My problems with the model are errors such as:

CheckWarmupConvergence: Loads Initialization, Zone="PERIMETER_BOT_ZN_1 ZN" did not converge after 25 warmup days;

SimHVAC: Exceeding Maximum iterations for all HVAC loops (which occurs 153 times)

HeatExchanger:AirToAir:SensibleAndLatent "HEAT EXCHANGER AIR TO AIR SENSIBLE AND LATENT 1": Average air volume flow rate is <50% or >130% warning continues;

and HeatExchanger:AirToAir:SensibleAndLatent "HEAT EXCHANGER AIR TO AIR SENSIBLE AND LATENT 1": Unbalanced air volume flow ratio exceeds 2:1 warning continues.

In addition, the primary air flow increases to the cooling design max rate even though the zone thermostat temperature is below the heating setpoint of 69.8 F (See the images below). I would like to know if the problem is with the way I set up the controls, the displacement ventilation models that I chose, the type of zones in which the DV systems are implemented, E+ difficulty modeling DV or something else.

Link to the file: https://www.dropbox.com/s/fu2ijqvngzu...

Thank you.

Jan 18, Weekday image description Jan 18, Weekday Morning Zoom image description March 08, Weekday March 08, Weekday Morning Zoom

edit retag flag offensive close merge delete