Buildings – heating and cooling

Buildings – heating and cooling
Thermal exchange with environment due to:
Conduction
Air exchange
Conduction
dQ
A
= k ΔT
dt
L
k = thermal conductivity (W/m/K)
k/L = thermal transmittance (W/m2/K) – a.k.a. U-value
kA/L = thermal conductance (W/K)
Air exchange
dQ
dt
Total consumption
1 dQ 1 ⎛ A
1
⎞
P=
= ⎜ k ΔT + NV ΔT ⎟
⎠
η dT η ⎝ L
3
1⎛ A 1
⎞
P = ⎜ k + NV ⎟ ΔT
⎠
η⎝ L 3
Hea$ng/cooling
efficiency
Building
leakiness
Weatherand
thermostat
Conduction
Conduction
Conduction
Thermostat
Energy rating
1kWh/y=0.114W
Combined heand and power
Combined heat and and power
Combined heat and and power
Ciclo di Carnot
Rendimento del ciclo di Carnot
L
η=
Q1
ΔEint = Q + L
L = Q1 − Q2
Q1 − Q2
Q2
η=
=1−
Q1
Q1
f
dQ
ΔS = ∫
T
i
ΔS1 = −ΔS2
Q1 Q2
=
T1
T2
T
η =1− 2
T1
Pompa di calore (riscaldamento)
Q1 1
T1
COP =
= =
L η T1 − T2
Frigorifero
Q2 1
T2
COP =
= =
L η T1 − T2
Heat pumps
Heat pumps
Howtoprepareforfinalpresenta$on
1.  Read the material and understand it
(rem tene, verba sequentur)
2. Do not start with powerpoint!
Take a blocknote and write down:
a.  Core message: 1 main point to take home, 1 sentence
b.  Introduction
c.  Conclusion
d.  Body: bullet list of arguments to present, with sublists
3. Prepare the slides (less than 10)
4. Practice, practice, practice (12 min duration)
(you need to remember by heart the whole bullet list of
things to say and be able to write it down without seing
the slides)