modelEffectiveness

Information

This block calculates the sensible and latent effectiveness of the heat exchanger under heating and cooling modes at different flow rates of the supply air and the exhaust air.

It calculates the ratio of the average operating flow rate to the nominal supply flow rate as

  rat = max(0.5, min(1.3, (mSup_flow + mExh_flow)/(2*mSup_flow_nominal))),

where mSup_flow is the mass flow rate of the supply air, mExh_flow is the mass flow rate of the exhaust air, mSup_flow_nominal is the nominal mass flow rate of the supply air, and rat is the flow ratio.

It then calculates the sensible and latent heat exchanger effectiveness by:

  epsSen = (epsSenPL + (epsSen_nominal - epsSenPL) * (rat - 0.75)/0.25),
  epsLat = (epsLatPL + (epsLat_nominal - epsLatPL) * (rat - 0.75)/0.25),

where epsSen and epsLat are the effectiveness for the sensible and latent heat transfer, respectively, epsSen_nominal and epsSenPL are the effectiveness for the sensible heat transfer when rat is 1 and 0.75, respectively, epsLat_nominal and epsLatPL are the effectiveness for the latent heat transfer when Rat is 1 and 0.75, respectively.

Note: The value of the rat is suggested to be between 0.5 and 1.3 during normal operation to ensure reasonable extrapolation. Likewise, an unbalanced air flow ratio less than 2, i.e., VSup_flow/VExh_flow > 0.5 and VSup_flow/VExh_flow < 2, is recommended.

References

U.S. Department of Energy 2016. "EnergyPlus Engineering Reference".

Parameters

Connectors

Revisions

• April 24, 2024, by Michael Wetter:
  Restricted flow ratio to valid region.
• September 29, 2023, by Sen Huang:
  First implementation.