HOURLY CALCULATION
METHOD (52016)
Principles
Application:
- energy need
- internal temp
- design heating/cooling need
Interval
Full year
Peak indoor temperature/
design load: > Short period
Assumptions
🖊 Mean radiant temp=
Average of internal temp of each elements
weighted on its area
External surfaces:
- External radiant env = external air temp
- Convective heat transfer = f( wind direction/speed ), time-independent
- Long-wave heat transfer = time-independent
Envelope:
- Thermal zone = closed, by elements
- Dimensions approach (internal/overall..) = const during assessement
- Thermo-physical prop = time-independent
- Spatial solar radiation distribution = time-independent
- Windows = solar angle-independent
- Solar energy = only transmitted
- Solar energy = only transmitted
Needs/loads
Basic:
- technical system always on
- system power unrestrictred
- only convective heat
- standard indoor conditions
System specific:
- characteristics/control
of technical bld system
Influences:
- may limited power
- convective fraction
- recoverable heat losses
- different temp set-points
- may limited H/C season
🖊 Energy need
Q
Sensible H/C:
- monthly, per Zone Thermally Conditioned
- annual, per zth
Latent for (de-)humidification:
- monthly, per zth
- annual, per zth
Internal temp calculation
- system-independent
For standard temp
-> Zero H/C power
-> Set max power=0
Sensible H load
🖊
- of a ztc
- for a sub-system
Climatic data (ISO 15927)
- Avg ext air temp = ext design temp
- Min hourly temp: must occur on avg 20 times in 20 years
- Initialization period=14 days
Internal gains = reduced by a factor f
Sensible C load
🖊
- of a ztc
- for a sub-system
Set-points & Internal gains:
simultaneity factors for usage data
--> none factors/data used directly
Climatic data:
same as H
Supply air condition
for (de-)Humidification
Calculation procedure
🖊 Thermal bridges
Overall heat transfer coefficient
H = Σ ( l Ψ ),
l: lengh ; Ψ: linear thermal trasmittance
Energy balance bld Element
🖊
- moisture load
- latent H load
Situations
None H/C / free floating condition
-> int temp calculated
Need C & sufficient
--> int temp = set-point
Need H & sufficient
--> int temp = set point
Need C - insufficient
--> int temp > set-point
Need H - insufficient
--> int temp < set-point
For each hour/zone -->
int op temp & actual H/C load
1) C/H needed?
2) Set-point apply? --> H/C load
3) H/C power sufficient?
4) If no: --> int temp
5) --> Actual H/C load
Opaque/Internal partition -->
2 on surfaces + 3 inside
Touching the ground -->
ext heat transfer coeff =
thermal conductance of ground layer
Windows/Doors --> 2
ISO 52016-1
Italian National Annex
Conductance btw nodes:
- h4 = h1 = 6/R
- h2 =h3 = 3/R
Classes:
- I (mass concentrated inwards)
- E (mass concentrated outwards)
- IE (mass divided over int & ext)
- D (mass equally distributed)
- M (mass concentrated inside)
Areal heat capacity k:
very light -- very heavy
no mass component -- > 12 cm bricks/concrete
- I --> k5=km
- E --> k1=km
- IE --> k1=k5=km/2
- D --> k1=k5=k/8 ; k2,3,4=km/4
- M --> k3=km
1) 🖊 Fourier number, each layer
2) Fo(ref)=0,5
3) 🖊 Number of capacity nodes (Ncn)
4) Number of nodes = S(Ncn) + 2
5) Data: mass density and thermal capacity per unit mass
6) Conductive resistance R= d / λ
7) Thickness associated to node Δx= d / Ncn
8) Areal thermal capacity, per node = ρ c Δx
9) Conductive resistance, per node = R / Ncn
10) Air gap --> k=0 ; h(i,e) = 2 ha
ha = convective-radiative air layer conductance
h = 1 / R
ISO 13789:
--> Area, Thermal resistance
ISO 13789 + 13370:
- Area ; Virtual ground temperature
- Floor effective thermal resistance (considering Ground)
- R & k of 0,5 ground layer
Also: Thermal transmittance U
- shuttered window
- curtain wall
Adjacent unconditioned
External
🖊 corrected thermal resistance of element
Internal
🖊 temp of unconditioned zone
VENTILATION:
- Heat transfer coefficient
PER HOUR
🖊 From outside
🖊 From unconditioned space
🖊 Thermal capacity of the ztc=
specific t.c. * area
🖊 Internal/Solar heat gains:
- Overall
- In the ztc
🖊 Solar shading
reduction factor
(Geometry)
🖊 Extra thermal radiation
to the SKY
🖊 (De-)Humidification load