STIEBEL ELTRON Heat pumps, Technical Manual

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Heat transfer medium
ethylene glycol was developed for use
as heat and cooling transfer medium.
the frost protection is subject to its
mixing ratio with water. the adjacent
frost protection curve illustrates that,
with a mixing ration of 30% ethylene
glycol and 70% water, the medium
remains liquid down to –18 °C and the
bursting effect begins at –25 °C.
subject to the mixing ratio, the system
pressure drop will also alter. in
accordance with the adjacent pressure
drop curve, the pressure drop with a
mixing ration of 30% to 70% increases
1.5-fold compared with water. take
this into account when sizing the
circulation pump.
Potassium carbonate KKs 30 can be
used as an alternative to ethylene
glycol. the product is adjusted to a
freezing point of -13 °C and must not
be mixed with either water or any
other refrigerant.
Physical details of the potassium carbonate KKS 30
temperature Density spec. thermal
capacity spec. thermal
conductivity
Kinematic viscosity
°C kg/m³ J/kgK w/mK mm²/s
+ 30 1261 3070 0.589 1.44
+ 20 1265 3055 0.572 1.75
+ 10 1270 3035 0.556 1.20
0 1274 3020 0.540 2.90
– 10 1278 3005 0.523 3.99
HEat tranSfEr mEdIUm
Frost protection of brine mixtures
Higher pressure drop of the brine mixture
liquid
icy
mush
burst effect
when frost
protection
is not achieved
(fixed)
Fr
os
t pr
ot
ection °C
Pr
es
sur
e
inc
re
ase f
actor