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Frontiers in Energy

ISSN 2095-1701

ISSN 2095-1698(Online)

CN 11-6017/TK

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Front. Energy    2014, Vol. 8 Issue (3) : 394-402    https://doi.org/10.1007/s11708-014-0310-1
RESEARCH ARTICLE
Evaluation of the performance of a centralized ground-water heat pump system in cold climate region
Shilei LU1,*(),Zhe CAI1,Li ZHANG2,Yiran LI1
1. School of Environmental Science and Engineering, Tianjin University, Tianjin 300072, China
2. China Aerospace Construction Group Co., Ltd., Beijing 100071, China
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Abstract

The aim of this study is to evaluate the performance of a centralized open-loop ground-water heat pump (GWHP) system for climate conditioning in Beijing with a cold climate in China. Thus, a long-time test was conducted on a running GWHP system for the heating season from December 2011 to March 2012. The analysis of the testing data indicates that the average heat-pump coefficient of performance (COP) and the COP of the system (COPs) are 4.27 and 2.59. The low value and large fluctuation in the range of COP are found to be caused by the heat transfixion in the aquifer and the bypass in the circulation loop. Therefore, some suggestions are proposed to improve the performance for GWHPs in the cold climate region in China.
Keywords ground-water heat pump (GWHP)      actual coefficient of performance      heat transfixion     
Corresponding Author(s): Shilei LU   
Online First Date: 25 July 2014    Issue Date: 09 September 2014
 Cite this article:   
Shilei LU,Zhe CAI,Li ZHANG, et al. Evaluation of the performance of a centralized ground-water heat pump system in cold climate region[J]. Front. Energy, 2014, 8(3): 394-402.
 URL:  
https://academic.hep.com.cn/fie/EN/10.1007/s11708-014-0310-1
https://academic.hep.com.cn/fie/EN/Y2014/V8/I3/394
Climate ValuesMonth
JanFebMarAprMayJunJulAugSepOctNovDec
Average outdoor temp/°C-3.8-1.67.714.419.424.526.525.620.412.95.4-0.5
Maximum outdoor temp/°C0.84.011.921.423.42930.631.328.118.19.95.6
Minimum outdoor temp/°C-9.9-7.70.27.013.115.923.222.615.66.9-0.1-7.1
Average relative humidity/%42.739.434.749.958.956.679.174.165.555.655.645.4
Total solar radiation/(MJ·m-2·d-1)253.4336.3463.6542.5594.5567.1531.4513.6400.8357.8263.8217.3
Average wind velocity/(m·s-1)2.62.43.02.82.42.42.01.92.02.02.12.5
Tab.1  Climate conditions in Beijing for long-term average values
Fig.1  Schematic diagram of the distribution of wells
NameSemi-hermetic screw ground water heat pump unit
Product typeLSBLGR-1400M
Refrigerating capacity/kW1104
Input power of cooling/kW220
Flow of chilled water/(m3·h-1)220
Flow of cooling water/(m3·h-1)251
Heating capacity/kW1569
Power input of heating/kW279
Flow of cold water/(m3·h-1)194
Flow of hot water/(m3·h-1)243
Unit dimension/m4465×1640×2118
Tab.2  Type and parameters of ground water heat pump unit
Fig.2  Schematic diagram of the ground water heat pump system
NameType and specificationNumberNote
Circulating loop pumpsType: QPG200-315Flow: 242 m3/hPump head: 27 mPower: 37 kW4Totally 4 pumps are installed, of which 1 is a spare unit
Immersible pumpType: KQL200/285-37/4Flow: 362 m3/hPump head: 24 mPower: 37 kW3Installed in well 1#、2#、4#
Tab.3  Auxiliary equipment lists
Measurement itemsTest intervalTest devicesRangeMeasurement accuracy
Water temperatureInlet and outlet of the evaporator10 minTR004 temperature sensor-30-125°C±0.5°C
Inlet and outlet of the condenser
Inlet and outlet of the circulation loop
Inlet and outlet of the ground water loop
FlowEvaporator10 minZRN-100 ultrasonic flowmeter1%
Condenser
Circulation loop
Ground water loop
Air temperatureIndoor air10 minTR002 temperature sensor-20-70°C±0.7°C
Outdoor air
Power consumptionHeat-pump unit10 minpower meter
System1day
Tab.4  Measurement items and device parameters
Temperature of ground water/°CTemperature difference of ground water loop/°CFlow of ground water/(m3·h-1)Temperature of supply water/°CTemperature difference of circulation water loop/°CFlow of circulation water loop/(m3·h-1)
Average value14–194–860–150441.5–4.5210–230
Design value155194455243
Tab.5  Operating parameters
Fig.3  Power consumption proportion
Fig.4  Weighted mean temperature of indoor air and outdoor air temperature
Fig.5  Amount of energy extracted from the groundwater (Qg), produced by the heat pump unit and inputted to the compressor (P) versus time in one day
Fig.6  Heat-pump COP in heating season
Fig.7  Heat-pump COP in one day
Gc/m3·h-1)Ge/m3·h-1)Tc,o/°CTe,i /°CCOP
220504014.54.41
158504014.54.46
220503814.54.70
158503814.54.72
220503614.54.99
158503614.55.03
Tab.6  Influence of condenser flow rate and outlet water temperature on COP
Gc/(m3·h-1)Ge/(m3·h-1)Tc,o/°CTe,i/°CCOP
220504018.05.02
220504016.54.80
220504014.54.41
Tab.7  Influence of evaporator inlet water temperature on COP
Fig.8  Performance coefficient of whole system (COPs) versus the day
Fig.9  Relationship between COPS and load factor
Fig.10  Variation of temperature of supply water (Ts) of the system, temperature of outlet water of the condenser (Tc,o), temperature difference between the supply and the return water (?T) of the system and the outlet and inlet of the condenser of the unit
Fig.11  The variation of ground water temperature
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