.BuildSysPro.IBPSA.Airflow.Multizone.DoorOperable

Information

Model for bi-directional air flow through a large opening such as a door which can be opened or closed based on the control input signal y.

For the control input signal y=1, this model is identical to IBPSA.Airflow.Multizone.DoorOpen, and for y=0, the door is assumed to be closed and the air flow rate is set to the air flow rate through the crack posed by the open door, V̇_clo.

The air flow rate for the closed door is computed as

V̇_clo = C_clo Δp^mClo,

where V̇_clo is the volume flow rate, C_clo is a flow coefficient and mClo is the flow exponent. The flow coefficient is

C_clo = L_clo C_DCloRat Δp_Rat^(0.5-mClo) (2/ρ₀)^0.5,

where L_clo is the effective air leakage area, C_DCloRat is the discharge coefficient at the reference condition, Δp_Rat is the pressure drop at the rating condition, and ρ₀ is the mass density at the medium default pressure, temperature and humidity.

The effective air leakage area L_clo can be obtained, for example, from the ASHRAE fundamentals (ASHRAE, 1997, p. 25.18). In the ASHRAE fundamentals, the effective air leakage area is based on a reference pressure difference of Δp_Rat = 4 Pa and a discharge coefficient of C_DCloRat = 1. A similar model is also used in the CONTAM software (Dols and Walton, 2002). Dols and Walton (2002) recommend to use for the flow exponent mClo=0.6 to mClo=0.7 if the flow exponent is not reported with the test results.

For the open door, the air flow rate V̇_ope is computed as described in IBPSA.Airflow.Multizone.DoorOpen with the parameters CDOpe and mOpe.

The actual air flow rate is computed as

V̇_clo = (y-1) V̇_clo + y V̇_ope,

where y ∈ [0, 1] is the control signal. Note that for values of y that are different from 0 and 1, the model simply interpolates the air flow rate between a fully open and a fully closed door. In practice, the air flow rate would likely increase quickly if the door is slightly opened, and hence we do not claim that the model is accurate for values other than y = 0 and y = 1.

References

• ASHRAE. ASHRAE Fundamentals, American Society of Heating, Refrigeration and Air-Conditioning Engineers, 1997.
• Dols and Walton. W. Stuart Dols and George N. Walton, CONTAMW 2.0 User Manual, Multizone Airflow and Contaminant Transport Analysis Software, Building and Fire Research Laboratory, National Institute of Standards and Technology, Tech. Report NISTIR 6921, November, 2002.

Revisions

• June 11, 2021, by Michael Wetter:
  Removed duplicate declaration of VABp_flow.
  This is for #1496.
• January 22, 2020, by Michael Wetter:
  Revised buoyancy-driven flow.
• October 6, 2020, by Michael Wetter:
  First implementation for #1353.