Deposition Sink

[amr-auf]

Hello all,

I have a question about modelling generic contaminant deposition, using
SurfaceContaminantSourceAndSink:Generic:DepositionVelocitySink
ZoneContaminantSourceAndSink:Generic:DepositionRateSink
The I/O reference for these classes mentions that "The removal stops when the sink concentration level is higher than the zone air concentration level."

I am struggling to understand how this rule is applied in detail and what the sink is in that case. I assume it will be the surface(s) the contaminant deposits onto?
If so, I have few more questions please:

• What are the sink concentration units? m3 of total deposited contaminant per m2 of surface area? I assume it cannot be in ppm, since the surface(s) do not technically have a volume.
• How does the calculation of sink concentration get accumulated over time? Does it follow the same prediction/correction approximation algorithms mentioned in the engineering reference? (backward order difference, euler, and analytical methods)
• Deposition models are based on Contam 3.0. However, Contam's guide does not mention that deposition stops when sink concentrations exceed room air concentrations. It has a deposition model that includes resuspension, where the sink releases contaminants back to air, but I do not think this model is based on comparing air concentrations to sink concentrations either. Is the concept of comparing air to sink concentrations specific to EnergyPlus?

Many thanks for your help.

All the best,
Amr

[mjwitte]

The relevant source code is here:

EnergyPlus/src/EnergyPlus/ZoneContaminantPredictorCorrector.cc

Lines 1530 to 1546 in 92ef604

	// From deposition velocity sink model
	for (auto &con : state.dataContaminantBalance->ZoneContamGenericDVS) {
	int SurfNum = con.SurfNum;
	int ZoneNum = state.dataSurface->Surface(SurfNum).Zone;
	Sch = con.depoVeloSched->getCurrentVal();
	GCGain = -con.DepoVelo * state.dataSurface->Surface(SurfNum).Area * Sch * state.dataContaminantBalance->ZoneAirGC(ZoneNum) *
	state.dataSurface->Surface(SurfNum).Multiplier * 1.0e-6;
	con.GenRate = GCGain;
	}
	// From deposition rate sink model
	for (auto &con : state.dataContaminantBalance->ZoneContamGenericDRS) {
	int ZoneNum = con.ActualZoneNum;
	Sch = con.depoRateSched->getCurrentVal();
	GCGain = -con.DepoRate * state.dataHeatBal->Zone(ZoneNum).Volume * Sch * state.dataContaminantBalance->ZoneAirGC(ZoneNum) * 1.0e-6;
	con.GenRate = GCGain;
	}

I do not see any tracking of the sink concentration or any test to cut off the deposition.

[amr-auf]

Hi Michael,

Many thanks for this clear and informative answer. The source code equations make sense, and are aligned with the equations in the I/O reference.

All the best,
Amr