PartialZone

Room air, long-wave exchange between its surfaces, distribution of the transmitted solar radiation

FastSmoothBuildings.Zones.PartialZone, partial model (source)

Purpose

Base class of the thermal zones: the heat balance of the room air, the long-wave exchange between the surfaces through a radiant star, the distribution of the transmitted solar radiation, infiltration, scheduled outdoor air and internal gains. Each surface connects to an element of propsBus. An extending class gives QVen, the heat brought by a ventilation system.

Equations

Long-wave exchange. Each surface i of emissivity ε_i, area A_i and temperature T_i exchanges with a radiant star through

G_i = 4 σ T_Lin³ ε_i A_i,   T_Rad = (∑ G_i T_i + Q_Rad,emi + A_Flo q_Rad) / ∑ G_i,

with T_Lin = T0Rad when linearizeRadiation is true, and otherwise the mean surface temperature weighted by ε_i A_i, explicit in the states of the surfaces. The radiant heat of the emitters (heaPorRad) and the radiant internal gains reach the surfaces in proportion to ε_i A_i; heaPorRad is at the mean surface temperature ∑ G_i T_i / ∑ G_i.

Transmitted solar radiation. With a_i and τ_i the solar absorptance and transmittance of the surfaces, each surface absorbs

• of the diffuse radiation the share a_i A_i / ∑ (a_j + τ_j) A_j;
• of the direct radiation, if the zone has floors: a floor a_i A_i / A_FloSur, and the other surfaces share what the floors reflect, in proportion to a_i A_i over the sum of (a_j + τ_j) A_j of the surfaces that are not floors; without floors, as the diffuse radiation.

The heat to the radiation side of surface i is G_i (T_Rad − T_i) plus its absorbed solar radiation.

Room air. With ρ = p_Atm/(R_Air T_Air) and ṁ_Ven the scheduled outdoor air flow,

f_mSen ρ c_p V dT_Air/dt = ∑ Q_con,i + Q_Con,emi + A_Flo q_Con + (ρ V ACH/3600 + ṁ_Ven) c_p (T_DryBul − T_Air) + Q_Ven,

where Q_con,i is the convective heat of surface i, held at T_Air, Q_Con,emi the heat of heaPorAir and q_Con, q_Rad the internal gains per floor area. The infiltration is a volume flow of zone air at the pressure of the site; ṁ_Ven is interpolated in ventilationSchedule by dayTable, repeated daily.

Parameters

Name	Default	Meaning
nSurf		number of surfaces
AFlo, hRoo		floor area and height
V	AFlo hRoo	air volume
ACH	0 1/h	air changes per hour by infiltration of outdoor air
ventilationSchedule	[0, 0]	outdoor air on top of the infiltration: time since midnight (s) and mass flow rate (kg/s); a step where the table repeats an instant
mSenFac	1	factor for the sensible heat capacity of the air
T_start	294.15 K	initial air temperature
hConInt, hConExt	0	fixed interior and exterior convection coefficients passed to the surfaces, 0 for the natural and the wind laws
T0Rad	293.15 K	linearization temperature of the long-wave exchange
linearizeRadiation	true	linearise at T0Rad, or at the current mean surface temperature

Relation to Buildings

After Buildings.ThermalZones.Detailed.MixedAir. The radiant star is the exact equivalent of the linearized radiosity exchange of Buildings with view factors A_j/∑ A; the transmitted solar radiation is distributed as in its SolarRadiationExchange; the infiltration is ACH V times the density of the zone air at the pressure of the site, as in Buildings. linearizeRadiation = true is the default of Buildings; false comes close to its exact exchange.

Use

Extended by Zone (no ventilation system) and VentilatedZone (supply and extract air).

Parameters

Parameter	Type	Unit	Default	Description
nSurf	Integer			Number of surfaces
AFlo	Real	m2		Floor area
hRoo	Real	m		Height
V	Real	m3	AFlo*hRoo	Air volume
ACH	Real	1/h	0	Air changes per hour by infiltration of outdoor air
ventilationSchedule	Real		[0, 0]	Day schedule of outdoor air brought in on top of the infiltration (night ventilation): time since midnight [s] and mass flow rate [kg/s], repeated daily; a step where the table repeats an instant, as trano's Buildings zone
mSenFac	Real		1	Factor for the sensible heat capacity of the air
T_start	Real	K	294.15	Initial temperature
hConInt	Real	W/(m2.K)	0	Fixed interior convection coefficient, 0 for the natural law
hConExt	Real	W/(m2.K)	0	Fixed exterior convection coefficient, 0 for the wind law
T0Rad	Real	K	293.15	Linearization temperature of the long-wave exchange
linearizeRadiation	Boolean		true	true: the long-wave exchange is linearised at T0Rad (Buildings' default); false: at the current mean surface temperature of the zone, close to the exact exchange of Buildings when it does not linearise

Revisions

• October 2026: moved from trano's FastModel.Zones.