Technical data

www.dimplex.de 01.2012 | Project planning manual for heat pumps for heating and domestic hot water preparation | 47
Brine-to-water heat pump 3.6
3.6 Heat source absorber systems (indirect use of air or solar energy)
Brine temperature range -15...+ 50 °C
Operating range of the brine-to-water heat pump-5 to +25 °C
Availability
Restrictions due to weather influences and limited surfaces pos-
sible.
Types of operation
 Bivalent
 Monovalent in combination with an additional ground heat
collector
Development costs
 Absorber system (energy roof, pipe bundle, solid absorber,
energy fence, energy tower, energy stack, etc.)
 Ethylene glycol or propylene glycol-based brine in a frost-
proof concentration
 Pipework and circulating pump
 Construction work
Pay special attention to:
 Building requirements
 Effects of the weather
Dimensioning absorber systems
Individual constructions vary considerably, so that the factory
specifications should normally be consulted when dimensioning
roof absorbers, energy towers and energy fences.
Experience has shown that the following data can be used as a
basis:
 The absorber surface should be designed according to the
specified off-peak (night time) output of the absorber.
 Even at temperatures over 0 °C, rain, dew or snow can
freeze on the surface of the absorber when the temperature
of the brine is very low. This could have a negative effect on
the heat flow rate.
 Monovalent operation is only possible in combination with
the utilisation of ground source heat.
 With the use of solar energy, brine can reach temperatures
of 50 °C or more in the transition period. Such temperatures
greatly exceed the operating range of the heat pump.
ATTENTION!
If the heat source temperature can rise to over 25 °C, then a temperature-
controlled mixer is required that, for temperatures over 25 °C, adds a
partial volume flow of the cooling water return flow to the cooling water
flow. (see Chapt. 3.5.2 on page 46)
Brine concentration
Due to the low outdoor temperatures, frost protection down to –
25 °C is necessary for roof absorbers, energy fences, etc. The
brine concentration for this system is 40%. When designing the
brine circulating pump, it should be taken into consideration that
the higher the brine concentration, the higher the pressure drops.
Filling the system:
The system should be filled as described in Chapt. 3.1.3 on
page 35.
Design of the expansion vessel:
The brine temperatures vary between approx. –15 °C and ap-
prox. +50 ° C for absorber-only operation. An expansion vessel
must be installed in the vicinity of the heat source system to ac-
commodate these large temperature fluctuations. The primary
pressure should be set to correspond to the height of the system.
The maximum overpressure is 2.5 bar.
Air pressure absorber
NOTE
If commissioning is carried out by the after-sales service and the anti-
freeze contains 30% monoethylene glycol, the lower operating limit can
be expanded to -10 °C!
Brine concentration: ≈ 40%
Relative pressure drop ≈ 1.8