ASHRAE Journal - January 2020 - 44

TECHNICAL FEATURE

(33 ft) to 40 m (131 ft). One test point was
FIGURE 3 Measured soil and weather temperature trends.
set at every 10 m (33 ft), and four test points
Main Span 2 10 (°C)
Main Span 2 20 (°C)
Main Span 2 30 (°C)
were set for each auxiliary monitoring well.
Main Span 2 40 (°C)
Outside Temperature
The water temperature sensor (Beijing
Seasons
Heating
Maintenance
Refrigeration Transitional
Kunlun Coast Sensing Technology Co., Ltd.,
China) of the heat pump was armored with
PT100 type thermal resistance, and 12 measuring points were arranged. The arrangement was as follows: there were eight
measuring points for the temperature of
return water supplied by the evaporator of
the heat pump unit and the temperature of
return water supplied by the condenser. In
addition, two measuring points for the total
return water temperature at the ground
A = annual fluctuation amplitude of surface
source side as well as two measuring points for the total
temperature,°C
return water temperature at the user side. A measureP = fluctuation period, d
ment flow ultrasonic flow sensor made four measureT = time, d
ment points: one total flow on the ground source side,
one total flow on the user side, one evaporator flow in
Modeling the GSHP System
the heat pump unit, and one condenser flow in the heat
The four operating conditions were adapted for
pump unit.
ground source heat pump system, namely, spring mainThe power parameter sensor was also set with four
tenance (Csp), summer cooling (Csm), autumn transimeasuring points. Two sets of them were used to meation (Ca) and winter heating (Cw) working conditions.
sure the power of the heat pump unit, another for meaAnalysis was conducted of the operational efficiency
suring the power of the ground source side-circulating
pump, and the last for measuring the user side circulat- index of the ground source heat pump system, using
the ground source heat pump unit and system COP as
ing pump quantity.
indicators. Relevant data obtained through the data
Temperature Field of Different Buried Pipe Spacing
monitoring system established during project construcTo meet the demand of heating, cooling and
tion is shown in Figure 3. It shows the different depths of
domestic hot water supply, Yang, et al., proposed a
the main hole and the outdoor temperature in the four
ground-source absorption heat pump (GSAHP) sysquarters from October 2015 to October 2016. During the
tem, where they simulated different heating/cooling/ heating season, the temperature of the main hole was
domestic hot water (HCD/DHW) systems in Beijing
initially high and then low, the highest was 9°C (48°F)
and Shenyang, and analyzed the soil thermal imbalin November, the lowest was in April, 7°C (45°F), the
ance, soil temperature, heat recovery and energy
fluctuation was not obvious; the outdoor temperature
18
efficiency. Changchun belongs to the high latitudes
fluctuated obviously, unstable within the range of 17°C
of China, and the annual variation of external tem(63°F) to 20°C (68°F). The highest and lowest temperaperature has a great influence on soil temperature.
tures appeared in March and January, respectively.
Periodic variation of surface temperature in the
During the maintenance season, the temperature of
ground is given by Equation 7;
the main hole inclined gently, stable at -4°C (25°F) to
4°C (39°F); the outdoor temperature varied between
2π
(7) 6°C (43°F) and 28°C (82°F), from low to high, rose in a
T f = T fm + A cos( t )
P
where
curved form. During the cooling season, the outdoor
Tf = the instantaneous temperature of the surface,°C temperature fluctuated between 22°C (72°F) to 30°C
Tfm = annual mean surface temperature,°C
(86°F), and the fluctuation range was not large; the main
44

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