DuctSeg

title: DuctSeg ---

Name Type Variability Description/Comments
ty choice:DUCTTY input time type: C_DUCTTYCH_RET / _SUP
Name Type Variability Description/Comments
absSlr number Start of subhour solar (SW) absorptance, dimless
awAbsSlr DBL Start of subhour
  • area-weighted solar absorptance
  • = sb_absSlr * area / zn_surfASlr
  • exterior surf outside: always 0
  • windows inside: TBD 12-8-10
  • ducts: always 0
epsLW number Start of subhour thermal (LW) emittance
zi TI Start of subhour adjacent zone idx, 0 if exposed to ambient
F DBL Start of subhour solar (short wave) fraction ? TODO: NOT USED? as of 4-2012
Fp DBL Start of subhour
  • "view factor" to zone radiant temp, dimless. Includes Oppenheim surface conductance.
  • aka "F-prime" in CZM documentation.
Name Type Variability Description/Comments
frRad DBL Start of subhour re radiant to radiant temp (room radiant node or sky)
fSky DBL Start of subhour "view factor" to radiant surround at sky temp
fAir DBL Start of subhour "view factor" to radiant surround at air temp (ground, horizon)
Name Type Variability Description/Comments
hcNat FLOAT_GEZ End of subhour surface natural convection coefficient, Btuh/ft2-F
hcFrc FLOAT_GEZ End of subhour surface forced (wind) convection coefficient, Btuh/ft2-F
hcMult FLOAT_GEZ End of subhour surface convection coefficient multiplier, dimless
hxa FLOAT_GEZ End of subhour overall coeff to sb_txa = sb_hcMult*(sb_hcNat + sb_hcFrc), Btuh/ft2-F
hxr FLOAT_GEZ End of subhour
  • surface (linearized) radiative coefficient, Btuh/ft2-F
  • = coupling to sb_txr
hxtot number End of subhour sb_hxa + sb_hxr
uRat DBL End of subhour
  • ratio uC/(sb_hxa + sb_hxr + uC)
  • = 1/(1 + rC*(sb_hxa + sb_hxr))
  • where uC = surface-to-surface conductance
  • rC = 1/uC
  • but: duct model outside surf to duct air
Name Type Variability Description/Comments
fRat DBL End of subhour
  • sb_hxtot * sb_uRat, Btuh/ft2-F
  • = overall conductance not including other side
  • surface resistances
  • (ducts: overall conductance from duct air to sb_txe)
cx DBL End of subhour air/radiant coupling due to this surface, Btuh/ft2-F
Name Type Variability Description/Comments
sgTarg solar gain target: bm, df gain from insolation
SGTARG
Name Type Variability Description/Comments
sgTarg.bm DBL End of subhour beam
sgTarg.df DBL End of subhour diffuse
sgTarg.tot DBL End of subhour total
sg DBL End of subhour absorbed solar total, Btuh (NOT Btuh/ft2), summed from sb_sgTarg
Name Type Variability Description/Comments
tSrf number End of subhour most recently calculated surface temp, F
tSrfls number Start of subhour
  • last step surface temp, F
  • copied from sb_tSrf at step end
  • not *e (available for probing)
qrAbs DBL End of subhour
  • total absorbed radiant heat gain at surface, Btuh/ft2 (+ = into surface)
  • = (sb_sg + sb_rIg)/area
txa number End of subhour
  • adjacent air temp, F (from prior step)
  • inside: prior step zone tz
  • outside: current step ambient dry bulb temp
txr number End of subhour
  • adjacent radiant temp, F
  • inside: prior step zone tr
  • outside: current step sky temp
txe number End of subhour
  • adjacent environmental temp, F
  • combined sb_txa and sb_txr; simplifies calcs in some cases
  • set but unused? for inside
  • set/used for ASHWAT outside
w DBL End of subhour
  • adjacent air humidity ratio if known (else 0)
  • used re duct leakage
qSrf DBL End of subhour
  • conduction into surface, Btuh/ft2
  • updated at end of timestep
Name Type Variability Description/Comments
pDS DUCTSEGP Start of subhour pointer to parent DUCTSEG
Name Type Variability Description/Comments
exArea FLOAT_GEZ input time
  • exterior heat transfer surface area, ft2 (outside of insulation)
  • if input, flat area-only model is used, many inputs have no effect
  • if NOT input, round ducts assumed
Name Type Variability Description/Comments
diam FLOAT_GZ input time duct diameter (w/o insulation), ft
len FLOAT_GEZ input time total length (all branches), ft
branchLen FLOAT_GZ Start of run average branch length, ft
branchCount SI_GZ input time # of branches
branchCFA FLOAT_GZ input time
  • floor area served per per branch, ft2
  • used re default ds_branchCount
airVelDs FLOAT_GZ input time
  • design air velocity, fpm
  • re flow-based sizing
Name Type Variability Description/Comments
inArea FLOAT_GEZ input time
  • interior surface area, ft2
  • = inside wetted area / duct surf area w/o insulation
  • (duct wall thickness assumed negligible)
Name Type Variability Description/Comments
insulR FLOAT_GEZ input time rated insulation resistance, ft2-F/Btuh
insulMati TI input time insulation material, 0 if none
Name Type Variability Description/Comments
insulKA DBL Start of run constants for insul conductivity: kInsul = kA + kB*T
insulKB DBL Start of run
insulThk FLOAT_GEZ Start of run insulation actual thickness, ft
insulThkEff number Start of run
  • effective insulation thickness, ft
  • includes outside/inside geometry effects
  • derived from input or estimated; can be 0
RconvIn DBL Start of phase
  • inside surfce convection resistance, ft2-F/Btuh
  • based on *exterior* area (i.e. value to be used in series with
  • effective duct insulation resistance; typ value = 0.4
Rduct DBL End of hour
  • total resistance from duct air to exterior surface of insulation
  • (not including exterior surface conductances), ft2-F/Btuh
  • based on *exterior* (exposed) area
  • updated hourly re temp-dependent insul conductivity
  • Never 0 assuming rs_RconvIn > 0
Uduct DBL End of hour 1/ds_Rduct
Name Type Variability Description/Comments
insulREff number End of hour
  • effective insulation resistance, ft2-F/Btuh
  • includes all adjustments for geometry and temperatures
Name Type Variability Description/Comments
exCnd choice:EXCND input time adjacent cond: adiabatic/ambient/specT/adjZn.
Name Type Variability Description/Comments
leakF number input time
  • leakage fraction, 0-1
  • return: leak is modelled at duct inlet (return register)
  • supply: leak is modelled at duct outlet (supply register)
uaTot DBL End of subhour
  • cur step total conductance between duct air
  • and surrounding equivalent temp, Btuh/F
Name Type Variability Description/Comments
beta number End of subhour
  • cur step conduction loss parameter (1 - effectiveness)
  • depends only on ds_uaTot and air mass flow
Name Type Variability Description/Comments
air[index] Array [4]
  • cur step air states
  • [ 0]=entering
  • [ 1]=after leak addition (return only)
  • [ 2]=average (consistent w/ conduction loss)
  • [ 3]=leaving
AIRSTATE
Name Type Variability Description/Comments
air[index].tdb DBL End of subhour air dry-bulb temp, F
air[index].w DBL End of subhour air humidity ratio, lb moisture/lb dry air
Name Type Variability Description/Comments
amfFL DBL End of subhour dry air mass flow rate at full load, lbm/hr
qCondFL DBL End of subhour
  • full load total conduction losses to surround (+ = out of duct), Btuh
  • (may be old: from last calc when rsMode != rsmOFF)
qCond DBL End of subhour
  • total conduction loss rate to surround (+ = out of duct), Btuh
  • (may be old: from last calc when rsMode != rsmOFF)
qCondAir DBL End of subhour ... to txa (air)
qCondRad DBL End of subhour
  • ... to txr (radiant)
  • ds_qCond = ds_qCondAir + ds_qCondRad
qLeakSen DBL End of subhour leakage sensible heat loss rate, Btuh (+ = out of duct)
qLeakLat DBL End of subhour leakage latent heat loss rate, Btuh (+ = out of duct)