Technical data

Generation of Refrigerating Capacity 2.2.2
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2 Generation of Refrigerating Capacity
2.1 Passive Cooling with Ground Water
In compliance with the VDI 4640 standard, most regions
welcome a cooling of the ground water e.g. through the use of a
heat pump for heating purposes. Increasing the temperature by
cooling, on the other hand, is only acceptable within strict limits.
A temperature of 20 °C must not be exceeded when the heat is
discharged into the ground water. In addition, the temperature
change of the ground water returned to the absorption well must
not exceed 6 K.
2.2 Active Cooling
Heat pumps for heating purposes operate with a refrigerating
circuit which can be reversed using a four-way reversing valve. In
the case of these reversible heat pumps, an existing temperature
level becomes “active”, i.e. it is cooled using the compressor
output of the heat pump.
2.2.1 Active Cooling with Reversible Brine-to-Water Heat Pumps
Active cooling with reversible brine-to-water heat pumps and
borehole heat exchangers is generally permissible up to a brine
temperature of 21 °C in the heat exchanger (average weekly
value) or a peak value of 25°C. Active cooling enables an
increase in the cooling capacity and yields constant flow
temperatures.
Heat exchanger design
The ground heat exchanger, which in heating operation serves
as a heat source for the brine-to-water heat pump, should be
designed according to the refrigerating capacity of the heat
pump. This can be calculated using the heat output minus the
electric power consumption of the heat pump as calculated in the
design.
The heat output to be discharged in cooling operation is
calculated using the cooling output of the heat pump plus the
electric power consumption of the heat pump as calculated in the
design.
NOTE
The heat output transferred to the ground heat exchanger in active
cooling operation is higher than the refrigerating output extracted in
heating operation.
2.2.2 Active Cooling with Reversible Air-to-Water Heat Pumps
Reversible air-to-water heat pumps utilise the inexhaustible
supplies of outside air for both heating and cooling. This means
that within the operating limits, it is only necessary to calculate
the maximum cooling load, not the total cooling requirements of
the entire cooling season. The refrigerating circuit of the heat
pump can generate flow temperatures between 7 and 20 °C at
an external temperature above 15 °C. These can be distributed
in the building using a water-bearing pipe system.
Temperature
outside air
Minimum Maximum
Heating -25°C +35°C
Cooling +15°C +40°C
Flow
temperature
Minimum Maximum
Heating +18°C
+58°C
1
1. at external temperatures to -10 °C and 40 °C at < -10 °C
Cooling +7°C +20°C