Modelling Heat Recovery in EnergyPlus and Contam

[Amr Auf]

Hi,

I have a general question on modelling heat recovery ventilation when coupling EnergyPlus and Contam.

How does Contam account for mixing of indoor and outdoor air, as a result of heat recovery, to evaluate indoor contaminant levels? I understand that some heat recovery systems entail mixing outdoor and indoor air to recover heat, while others use different type of heat exchangers without mixing indoor and outdoor air. Will indoor contaminant levels differ in both cases?

Should I adjust the percentage of outdoor air flow in Contam to account for these different behaviours (i.e., use a percentage of air recirculation to account for air mixing)? 

Please let me know if I have fundamental misunderstanding about HRV modelling in Contam works. Your kind help is very much appreciated.

All the best,

Amr

[Dols, William Stuart (Fed)]

Amr,

 

EnergyPlus can employ multiple types of HRV/ERVs in various locations of the model, e.g., at the OA intake to an AirLoopHVAC or directly to a zone via a ZoneHVAC:EnergyRecoveryVentilator. CONTAM3DExporter will only generate that latter as indicated in the CONTAM User Guide. However, once 3DExporter generates the IDF file, you can add a Heat Exchanger to the outdoor air intake of an air loop. I would suggest using OpenStudio to create simple test cases and review the IDF files generated to understand the node connectivity of the Air Loop case.

 

In both cases, the outdoor airflows (system flows) are controlled via EnergyPlus and provided to the associated Simple AHS in the CONTAM model during co-simulation. You should be able to account for crossover by controlling the fraction of outdoor air (hence recirculated air) provided via an OA controller associated with the HRV/ERV. You may accomplish this via an OA schedule or EMS Programming in EnergyPlus.

 

I always recommend starting with a simple test case to learn how the coupling works before getting too involved. The NIST Multizone Modeling website provides a simple example (MZ320…, not including EMS) that demonstrates the scheduling of the fraction of Outdoor Air provided via a Simple AHS/AirLoopHVAC.
https://www.nist.gov/el/energy-and-environment-division-73200/nist-multizone-modeling/software/contam-3d-exporter#Examples

 

- Stuart

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