Φορτία
-Συσκευές σε κατοικίες: Appliance loads are concentrated mainly in the kitchen and laundry areas. Based on
contemporary living conditions in single-family houses, a sensible load of 470 W should be divided between
the kitchen and/or laundry (ASHRAE 1997)
Θεωρία
Heat gains vs cooling loads
SOL-AIR TEMPERATURE (ASHRAE 1997)
Sol-air temperature is the temperature of the outdoor air that, in the absence of all radiation changes, gives
the same rate of heat entry into the surface as would the combination of incident solar radiation, radiant
energy exchange with the sky and other outdoor surroundings, and convective heat exchange with the
outdoor air.
Heat Flux into Exterior Sunlit Surfaces. The heat balance at a sunlit surface gives the heat flux into the
surface q/A as
q A = It + hoto – ts– R
where
= absorptance of surface for solar radiation
It = total solar radiation incident on surface, W/m2
ho = coefficient of heat transfer by long-wave radiation and convection
at outer surface, W/m2 · K
to = outdoor air temperature, °C
ts = surface temperature, °C
= hemispherical emittance of surface
R = difference between long-wave radiation incident on surface from
sky and surroundings and radiation emitted by blackbody at outdoor
air temperature, W/m2
Assuming the rate of heat transfer can be expressed in terms of the sol-air temperature te
q A = hote – ts 
te = to + It ho – R ho

Horizontal Surfaces. For horizontal surfaces that receive long-wave radiation from the sky only, an
appropriate value of ∆R is about 63 W/m2, so that if ε = 1 and ho = 17.0 W/(m2 · K), the long-wave correction
term is about −3.9°C (Bliss 1961).
Vertical surfaces. Because vertical surfaces receive long-wave radiation from the ground and surrounding
buildings as well as from the sky, accurate ∆R values are difficult to determine. When solar radiation intensity
is high, surfaces of terrestrial objects usually have a higher temperature than the outdoor air; thus, their
long-wave radiation compensates to some extent for the sky’s low emittance. There-fore, it is common
practice to assume ∆R = 0 for vertical surfaces.
TETD/TA - 1967
Transfer Function Method (TFM) – 1972
CLTD/SCL/CLF - 1977
Radiant Time Series (RTS) – 2001
Θερμοκρασίες εδάφους Αθήνας
Heat Transfer Processes (ASHRAE 1997)
Thermal Conduction. This is the mechanism of heat transfer whereby energy is transported between parts
of a continuum by the transfer of kinetic energy between particles or groups of particles at the atomic level.
In gases, conduction is caused by elastic collision of molecules; in liquids and electrically nonconducting
solids, it is believed to be caused by longitudinal oscillations of the lattice structure. Thermal conduction in
metals occurs, like electrical con-duction, through the motion of free electrons. Thermal energy trans-fer
occurs in the direction of decreasing temperature, a consequence of the second law of thermodynamics. In
solid opaque bodies, thermal conduction is the significant heat transfer mechanism because no net material
flows in the process. With flowing fluids, thermal conduction dominates in the region very close to a solid
boundary, where the flow is laminar and parallel to the surface and where there is no eddy motion.
Thermal Convection. This form of heat transfer involves energy transfer by fluid movement and molecular
conduction (Burmeister 1983, Kays and Crawford 1980). Consider heat transfer to a fluid flowing inside a
pipe. If the Reynolds number is large enough, three different flow regions exist. Immediately adjacent to the
wall is a laminar sublayer where heat transfer occurs by thermal conduction; outside the laminar sublayer is
a transition region called the buffer layer, where both eddy mixing and conduction effects are significant;
beyond the buffer layer and extending to the center of the pipe is the turbulent region, where the dominant
mechanism of transfer is eddy mixing.
In most equipment, the main body of fluid is in turbulent flow, and the laminar layer exists at the solid walls
only. In cases of low-velocity flow in small tubes, or with viscous liquids such as oil (i.e., at low Reynolds
numbers), the entire flow may be laminar with no transition or turbulent region.
When fluid currents are produced by external sources (for example, a blower or pump), the solid-to-fluid
heat transfer is termed forced convection. If the fluid flow is generated internally by non-homogeneous
densities caused by temperature variation, the heat transfer is termed free convection or natural convection.
Thermal Radiation. In conduction and convection, heat trans-fer takes place through matter. In thermal
radiation, there is a change in energy form from internal energy at the source to electromagnetic energy for
transmission, then back to internal energy at the receiver. Whereas conduction and convection are affected
primarily by temperature difference and somewhat by temperature level, the heat transferred by radiation
increases rapidly as the temperature increases.
Συστήματα
www.michanikos.gr
Να κάνω μια πιο απλοική ερώτηση για αρχή: σε περίπτωση που στο επιθεωρούμενο κτίριο δεν έχουμε
συστήματα διαχείρησης φυσικού φωτισμού (αισθητήρες κλπ) τότε με βάση την παρ.6.1.3.2 (σελ48755
ΤΟΤΕΕ) δεν αξιολογούμε τις ζώνες φυσικού φωτισμού και τις αγνοούμε, σωστά?
Άρα στην καρτέλα του φωτισμού στο λογισμικό, στις "ζώνες τεχνητού φωτισμού" ως ποσοστό εισάγουμε
100% στην στάθμη εκείνη στην οποία ανήκει το επιθεωρούμενο κτίριο βάσει χρήσης, πχ για
γραφεία/καταστήματα στην στάθμη 500 lx? Και στις υπόλοιπες εισάγουμε μηδενικά ποσοστά?
Επιπλέον, αναλύω λίγο το σκεπτικό μου για να υπολογίσουμε την εγκατεστημένη ισχύ και μου λέτε αν είναι
σωστό:
Από πίνακα 5.1α (σελ 48753 ΤΟΤΕΕ1) με βάση και το τί τύπο φωτιστικών έχω πραγματικά εγκατεστημένα
στο κτίριο επιλέγω πυκνότητα ισχύος ανά 100lx, σε μονάδες W/m2/100lx. Αυτό το νούμενο το
πολλαπλασιάζω με τα m2 του κτιρίου μου (ή της ζώνης) και επί την στάθμη φωτισμού σε lx από πίνακα 2.4,
αναλόγως χρήσης κτιρίου.(δεν ξεχνώ κατά την πράξη να διαιρέσω με τα 100lx, και έτσι έχω βρει την
ελάχιστη απαιτούμενη ισχύ σε kW). Την συγκρίνω με την πραγματικά εγκατεστημένη ισχύ, που είναι
άθροισμα εγκατεστημένων λαμπτήρων επί την ισχύ τους.Εάν η πραγματικά εγκατεστημένη είναι μικρότερη
από την ελάχιστη απαιτούμενη έως και 30% προς τα κάτω, βάζω την ελάχιστη απαιτούμενη. Σωστά?