.Buildings.Fluid.HeatExchangers.ThermalWheels.Sensible.BaseClasses.Effectiveness

Information

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

It first calculates the ratio of the average operating flow rate to the nominal supply flow rate by:

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

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

It then calculates the sensible heat exchanger effectiveness as

  eps = (epsPL + (eps_nominal - epsPL) * (rat - 0.75)/0.25),

where eps is the effectiveness for the sensible heat transfer, respectively, eps_nominal and epsPL are the effectiveness for the sensible 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., mSup_flow/mExh_flow > 0.5 and mSup_flow/mExh_flow < 2 is recommended.

References

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

Revisions

• April 24, 2024, by Michael Wetter:
  Restricted flow ratio to valid region.
• January 8, 2024, by Sen Huang:
  First implementation.