Bosch Geothermal Heat Pumps Applications Manual page 14

1 4 | Bosch Geothermal Heat Pumps
4.4.2 Cooling Cycle
The cooling cycle is basically the reverse of the heating
cycle. The direction of the refrigerant ow is changed
by the reversing valve. In the cooling mode, the water
circulating in the earth loop is warmer than the
surrounding ground. This causes the water to release
heat into the earth. The water which is now cooler
from traveling through the ground ows to the water-
to-refrigerant coaxial heat exchanger in the geothermal
heat pump (Fig. 14). In the water-to-refrigerant coaxial
heat exchanger, hot refrigerant gas from the compressor
releases its heat into the water. This causes the water to
increase in temperature, which it releases to the ground.
The refrigerant, which has released its heat energy and
became a cold liquid, now, travels to the refrigerant-to-
air heat exchanger. The cool, liquid refrigerant enters
the refrigerant-to-air heat exchanger during cooling.
As it enters the refrigerant-to-air heat exchanger, the
temperature of the refrigerant is relatively cool (around 50
degrees). Here the geothermal heat pump's blower
Fig. 14 Water-to-air cooling cycle
Data subject to change
circulates warm, humid air across the cold refrigerant-to-
air heat exchanger. The refrigerant in the refrigerant-to-air
heat exchanger absorbs the heat energy from the air (and
dehumidi es the air) and travels to the compressor, which
raises the pressure so it will move through the system.
The increased pressure from the compressor causes the
refrigerant to heat up. The refrigerant picks up heat from
the structure air via the return duct system and transfers
it directly to the groundwater or water and antifreeze
mixture. The heat is then pumped outside, into the
underground piping (in the case of a closed-loop system)
to start the cycle again. Some of this excess heat can be
used to pre-heat domestic hot water.
Unlike air-source heat pumps, geothermal heat pumps do
not require a defrost cycle. Temperatures underground
are much more stable than air temperatures, and the
geothermal heat pump unit itself is located inside;
therefore, the same problems with frost do not arise.
Applications Manual
Bosch Thermotechnology Corp.