4.26 DUCTSEG
DUCTSEG defines a duct segment. Each RSYS has at most one return duct segment and at most one supply duct segment. That is, DUCTSEG input may be completely omitted to eliminate duct losses.
dsName
Optional name of duct segment; give after the word “DUCTSEG” if desired.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| 63 characters | none | No | constant |
dsTy=choice
Duct segment type.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| SUPPLY, RETURN | Yes | constant |
The surface area of a DUCTSEG depends on its shape. 0 surface area is legal (leakage only). DUCTSEG shape is modeled either as flat or round –
- dsExArea specified: Flat. Interior and exterior areas are assumed to be equal (duct surfaces are flat and corner effects are neglected).
- dsExArea not specified: Round. Any two of dsInArea, dsDiameter, and dsLength must be given. Insulation thickness is derived from dsInsulR and dsInsulMat and this thickness is used to calculate the exterior surface area. Overall inside-to-outside conductance is also calculated including suitable adjustment for curvature.
dsBranchLen=float
Average branch length.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| ft | x \(>\) 0 | -1.0 | No | constant |
dsBranchCount=integer
Number of branches.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| x \(>\) 0 | -1 | No | constant |
dsBranchCFA=float
Floor area served per branch
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| ft2 | x \(>\) 0 | -1.0 | No | constant |
dsAirVelDs=float
Specified air velocity design.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| fpm | x \(>\) 0 | -1.0 | No | constant |
dsExArea=float
Duct segment surface area at outside face of insulation for flat duct shape, see above.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| ft2 | x \(\ge\) 0 | none | No | constant |
dsInArea=float
Duct segment inside surface area (at duct wall, duct wall thickness assumed negligible) for round shaped duct.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| ft2 | x \(\ge\) 0 | Derived from dsDiameter and dsLength | (see above reduct shape) | constant |
dsDiameter=float
Duct segment round duct diameter (duct wall thickness assumed negligible)
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| ft | x \(\ge\) 0 | Derived from dsInArea and dsLength | (see above reduct shape) | constant |
dsLength=float
Duct segment length.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| ft | x \(\ge\) 0 | Derived from dsInArea and dsDiameter | (see above reduct shape) | constant |
dsExCnd=choice
Conditions surrounding duct segment.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| ADIABATIC, AMBIENT, SPECIFIEDT, ADJZN | ADJZN | No | constant |
dsAdjZn=znName
Name of zone surrounding duct segment; used only when dsExCon is ADJZN. Can be the same as a zone served by the RSYS owning the duct segment.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| name of a ZONE | none | Required when dsExCon = ADJZN | constant |
dsEpsLW=float
Exposed (i.e. insulation) outside surface exterior long wave (thermal) emittance.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| 0 \(\le\) x \(\le\) 1 | 0.9 | No | constant |
dsExT=float
Air dry-bulb temperature surrounding duct segment.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| oF | unrestricted | none | Required if sfExCnd = SPECIFIEDT | hourly |
dsInsulR=float
Insulation thermal resistance not including surface conductances. dsInsulR and dsInsulMat are used to calculate insulation thickness (see below). Duct insulation is modeled as a pure conductance (no mass).
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| ft2-oF-hr / Btu | x \(\ge\) 0 | 0 | No | constant |
dsInsulMat=matName
Name of insulation MATERIAL. The conductivity of this material at 70 oF is combined with dsInsulR to derive the duct insulation thickness. If omitted, a typical fiberglass material is assumed having conductivity of 0.025 Btu/hr-ft2-F at 70 oF and a conductivity coefficient of .00418 1/F (see MATERIAL). In addition, insulation conductivity is adjusted during the simulation in response its average temperature. As noted with dsInsulR, duct insulation is modeled as pure conductance – MATERIAL matDens and matSpHt are ignored.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| name of a MATERIAL | fiberglass | No | constant |
dsLeakF=float
Duct leakage. Return duct leakage is modeled as if it all occurs at the segment inlet. Supply duct leakage is modeled as if it all occurs at the outlet.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| 0 \(<\) x \(\le\) 1 | none | No | constant |
dsExH=float
Outside (exposed) surface convection coefficient.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| Btuh/ft2-oF | x \(\ge\) 0 | .54 | No | subhourly |
endDuctSeg
Optionally indicates the end of the DUCTSEG definition.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| none | No | constant |
Related Probes: