ASHRAE Journal - January 2020 - 39

TECHNICAL FEATURE

determined that the COP of a ground source heat pump
project in Tianjin area (outdoor calculated average temperature of air conditioning during summer was 29.3°C
(84.7°F) while the outdoor calculated average temperature of air conditioning in winter was -9.4°C (15.1°F))
was about 3.4 and COP of 2.8 at different times.9 Liu Jun
et al. conducted a simulation study in Shanghai (outdoor
calculated average temperature of air conditioning in
summer was 31.3°C (88.3°F), outdoor calculated average temperature of air conditioning in winter was -1.2°C
(29.8°F). Outdoor calculated average temperature of air
conditioning in winter is -9.4°C (15.1°F), where it is hot
in summer and cold in winter. It was concluded that
when the thermal and thermal load unbalance rate was
10%, the soil temperature showed an overall upward
trend after ﬁve years of operation. However, it had little
effect on the heat transfer performance of the system
in winter and summer, and the temperature rise of the
soil temperature in the ﬁrst three years of operation was
relatively large.10-12
Hu Zhigao et al., in their study established a ground
source heat pump test bench to analyze the geothermal
characteristics of the soil heat pump before and after
operating in the hot summer and cold winter zone in
Wuhan. They concluded that the temperature change
of underground soil at 30 m (98 ft) was stable, and was
more conducive to heat pump operation.13 Other studies
simulated the soil source heat pump system in the cold
region with and without compensation.14-15
In summary, the operating efﬁciency of the fully
available ground source heat pump depends on
the local climatic conditions, soil thermal properties parameters and heating/cooling load. Moreover,
areas with large differences in cooling and heating
demands tend to have relatively small COP values in
buildings. Therefore, since the ground source heat
pump is widely promoted in severely cold regions, it is
necessary to overcome the problem of low COP caused
by the large difference between annual total cooling
capacity and heating capacity. In this article, a method
is proposed to improve the difference between cooling capacity and heating capacity with a larger annual
difference, which can be used to monitor the operation of the system in relation to the ground. Again, the
study proposes a method to improve the difference
between refrigerating capacity and heat production.
The novelty is the introduction of a type of hot and

cold balance. Matching thermal equilibrium by using
area control method and surrounding soil to supplement the system with soil. In winter, the working area
of air conditioning and heating is 5000 m2 (53,820 ft2)
and 10 000 m2 (107,639 ft2) in summer as the working
area of refrigeration. In the transitional season, the
soil is reﬁlled directly by the pump. The relationship
between the local climatic environment temperature
and geological conditions and the load characteristics
of buildings in the design and operation regulation of
soil source heat pump was fully analyzed.

Soil Source Heat Pump Project Engineering and
Description of the Testing Situation
GSHP Project Introduction

This study chose a teaching hall of Jilin University
of Architecture located in a cold region, Changchun
city, Jilin-China, as a demonstration project of the
ground source heat pump (heating/cooling). The total
construction area of the teaching building was 34
882.24 m2 (375,469 ft2), the air-conditioning/heating
area during winter was 5000 m2 (53,820 ft2) while the
area for cooling in summer was 10 000 m2 (107,639 ft2).
The entire cooling capacity was 423.6 kW as the total
heating capacity was 373.2 kW with a 50-year design
service life.
According to a study by Antonio Capozza, et al., the
imbalance of ground temperature is the key factor affecting the thermal ﬂow, and the number of boreholes has no
signiﬁcant effect on the thermal ﬂow.16 Therefore, there
was a central heat pump room on the ground ﬂoor of the
teaching building, equipped with two heat pump units
and six circulating pumps. The double U-shaped vertical buried pipes were used to set 120 heat exchange wells
with a depth of 100 m (328 ft) and a diameter of 180 mm
(7 in.). The well spacing of the heat-exchange well group
was divided into L-type and array-type L-type wells with a
spacing of 5 m (16 ft), considering the actual well location
conditions and scientiﬁc research needs. The well spacing
of the array-placed wells was set to 4 m (13 ft), 5 m (16 ft),
and 6 m (20 ft), respectively. The heat exchanger well layout is shown in Figure 1.
According to the results of on-site geological exploration: 0 to 8 m (26 ft) was mainly composed of clay and
silty clay; 8 to 23 m (26 to 75 ft) was mainly coarse sand
and medium coarse sand; weakly weathered and moderately weathered mudstone and glutenite made up
JAN UARY 2020

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