Geothermal Cooling - Low Energy Cooling for Sustainable Buildings - page 95

4 40

3 30

2 20

1 10

0 0

20 21 23 24 26

Date in June

27 28 30

-1 -10

-2 -20

Cooling power
COP

-3 -30

-4 -40

Figure 4.11 Cooling power and COP of horizontal brine heat exchanger in the ebok building during
summer 2005

during the last 2 days due to the relatively warm soil temperature. This high soil
temperature is mainly due to the shallow depth of the pipes.
The ambient air can be cooled down by as much as 7 K in the heat exchanger.
However, supply air to the building is still at 28 ◦ C during midday. The soil temperature
rises up to nearly 20 ◦ C at the end of June (see Figure 4.12). The logarithmic average
temperature difference of brine and air across the heat exchanger is about 6 . 3K.

4.1.3 Performance of Vertical Earth Brine to Air Heat Exchanger
in the SIC Building

In the SIC building, the main cooling strategy is mechanical night ventilation. Only
a seminar room with a floor area of 178m 2 and the lobby area of the building with a

40

Air before HX
Air after HX

35

30

25

20

Brine return from HX
Brine supply to HX

15

10

16.6 18.6 20.6 22.6 24.6 26.6 28.6 30.6

Figure 4.12 Horizontal heat exchanger performance with temperature levels of the brine supply to the
heat exchanger (HX) and its return, as well as the ambient air before the HX and after in summer 2005