SimZone

Basically, the simple zone Model describes a volume of well-mixed air that is bounded by surfaces shaped as non-self-intersecting polygons. This volume is regarded as a closed physical system in which the basic conservation laws are applied:

Mass balance

Air can be transported into (positive) or out of (negative) the zone. This happens through air terminals. Each zone has at least one such air terminal (air terminal 0), plus an optional number (nTerminal) of additional air terminals. The cause of air transport carried out through air terminals can be:

• Air infiltration from either ambient or neighboured zones through leaks
• Ventilation inlets (supply air) or outlets (exhaust air)
• Open windows or doors
• Chimneys or shafts
• Porous walls
• etc.

Heat balance

Heat can be supplied to (positive) or removed from (negative) the zone. This happens through either air terminals (heat transport), thermal bridges, zone surfaces (heat convection and longwave radiation), internal heat sources (occupants, equipments, lights) or active heating/cooling units. Supplied or removed heat always causes either a change in the air temperature (sensible heat) or the air humidity (latent heat) of the zone. The cause of supplied/removed heat can be:

• Convection from occupants occ.QCv2Zone = sum(occ.QCv) where
  QCv = nAct*1.8* (fCl*hClCv*(TClOpt-TAir) + 0.0014*M*58.15*(34-TAir));
• Convection from equipment equip.QCv2Zone = equip.schedule*equip.QSrcCv
• Convection from lights light.QCv
• Convection from heating/cooling units backside hc.item.QBack
• Other convection (from "convective devices") cvDev.Q
• Transport through air terminals (infiltration, mechanical or natural ventilation, etc.) term.Q_0 and term.item.Q
• Convection from local heating and cooling units locUnit.QCv
• Condensation at local cooling units locUnit.QCond
• Transport of condensed vapor at local cooling units CP_WAT * locUnit.item.Wf * locUnit.item.Tcoil
• Convection from external wall surfaces surf.item[k].hA * (surf.item[k].T - TAir)
• Convection from window surfaces opn.QCv
• Convection from internal wall surfaces intWall.hA*(intWall.T-TAir)
• Latent heat from occupants (HF_VAP + 30*CP_VAP) * occ.VapF2Zone
• Latent heat from equipment equip.QLat2Zone
• Convection losses from heating and cooling distribution ducts QLossIn

Long wave radiation balance

Radiated heat does not directly affect the zone air, but the zone surfaces. They will then be heated or cooled and can exchange heat with the zone air secundarily. In contrast to the detailed zone model (the "Climate" zone model GgZone), the long-wave radiation exchange does not occur directly from one radiating body to every other, but each radiating body exchanges radiant heat with a central radiation node of mean radiation temperature TMrt. The sum of all emitted radiation is equal to the sum of all received radiation. The cause of radiated heat can be:

• Longwave radiation from lights light.QLw
• Longwave radiation from occupants occ.QLw2Zone
• Longwave radiation from equipment equip.QLw2Zone
• Longwave radiation from heating/cooling units that are not represented as a zone surface locUnit.QLw
• Other longwave radiation (from "radiative devices") radDev.Q
• Longwave radiation to (and from) zone surfaces QLw2Surf

Zone surfaces

A zone can be bounded by the following types of surfaces:

• ExtWall: Wall surfaces at the zone border
• IntWall: Surfaces of walls located completely inside the zone
• HCSurf: Heating and cooling sufaces at the zone border
• Opn: Surfaces of windows and openings at the zone border

Surface heat balance

The surface heat balances (one for each zone surface) connect the zone air heat balance with the longwave radiation balance. The contributions to the surface heat balance are:

• Heat conducted from the inner of the wall to its surface TqWall.Q[i]
• Longwave radiation from and to the central radiation node QLw2Surf[i]
• Shortwave (= solar) radiation absorbed by the surface QSw2Surf[i]
• Heat convection from and to the zone air QCvFromSurf[i]