HOW A HEAT PUMP MOVES HEAT UPHILL
FIG. 1 · VAPOUR-COMPRESSION CYCLE
2 °C
OUTSIDE
21 °C
INSIDE
ΔT = +19 K, UPHILL
left alone, heat only flows hot → cold
OUTSIDE · 2 °C
INSIDE · 21 °C
EXTERIOR WALL
HEAT IN
from 2 °C air
HEAT OUT
to 21 °C room
W
① EVAPORATOR
−5 °C: colder than
the air, so heat flows in
② COMPRESSOR
electric work squeezes the gas
→ ≈24 bar, ≈70 °C
③ CONDENSER
≈40 °C: hotter than
the room, so heat flows out
④ EXPANSION VALVE
pressure drops 24 → 7 bar,
it chills to −5 °C
LOW SIDE ≈ 7 bar
HIGH SIDE ≈ 24 bar
−5 °C
LOW PRESSURE · COLD
HIGH PRESSURE · HOT
REFRIGERANT R-410A
TYPICAL VALUES · NTS
KEY IDEA
A heat pump doesn't make heat.
It moves it, uphill.
2.5 kWh · outdoor air
+ 1 kWh · electricity
= 3.5 kWh · into the room
COP ≈ 3.5
typically 3–4 units of heat per unit of electricity