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Frontiers in Energy

ISSN 2095-1701

ISSN 2095-1698(Online)

CN 11-6017/TK

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Front. Energy    2015, Vol. 9 Issue (3) : 343-361    https://doi.org/10.1007/s11708-015-0372-8
RESEARCH ARTICLE
Optimization model analysis of centralized groundwater source heat pump system in heating season
Shilei LU(),Yunfang QI,Zhe CAI,Yiran LI
School of Environmental Science and Engineering, Tianjin University, Tianjin 300072, China
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Abstract

The ground-water heat-pump system (GWHP) provides a high efficient way for heating and cooling while consuming a little electrical energy. Due to the lack of scientific guidance for operating control strategy, the coefficient of performance (COP) of the system and units are still very low. In this paper, the running strategy of GWHP was studied. First, the groundwater thermal transfer calculation under slow heat transfixion and transient heat transfixion was established by calculating the heat transfer simulation software Flow Heat and using correction factor. Next, heating parameters were calculated based on the building heat load and the terminal equipment characteristic equation. Then, the energy consumption calculation model for units and pumps were established, based on which the optimization method and constraints were established. Finally, a field test on a GWHP system in Beijing was conducted and the model was applied. The new system operation optimization idea for taking every part of the GWHP into account that put forward in this paper has an important guiding significance to the actual operation of underground water source heat pump.
Keywords optimization model      groundwater source heat pump system      theoretical analysis      example verification      heating season     
Corresponding Author(s): Shilei LU   
Just Accepted Date: 03 July 2015   Online First Date: 21 August 2015    Issue Date: 11 September 2015
 Cite this article:   
Shilei LU,Yunfang QI,Zhe CAI, et al. Optimization model analysis of centralized groundwater source heat pump system in heating season[J]. Front. Energy, 2015, 9(3): 343-361.
 URL:  
https://academic.hep.com.cn/fie/EN/10.1007/s11708-015-0372-8
https://academic.hep.com.cn/fie/EN/Y2015/V9/I3/343
Fig.1  Working points of pump
Fig.2  Flowchart of optimization process of GWHP system
Name Semi-hermetic screw groundwater heat pump unit
Type LSBLGR-1400M
Refrigerating capacity/kW 1104
Input power of cooling/kW 220
Flow of chilled water/(m3·h-1) 220
Flow of cooling water/(m3·h-1) 251
Heating capacity/kW 1569
Power input of heating/kW 279
Flow of cold water/(m3·h-1) 194
Flow of hot water/(m3·h-1) 243
Tab.1  Types and parameters of GWHP unit
Name Type and specification Number Note
Circulating pump Type: QPG200-315 4 Totally 4 pumps are installed, of which 1 is a spare unit
Flow: 242 m3/h
Pump head: 27 m
Power: 37 kW
Submersible pump Type: KQL200/285-37/4 3 Installed in Well 1, 2,and 4
Flow: 362 m3/h
Pump head: 24 m
Power: 37 kW
Tab.2  Types and parameters of pumps
Type Heat dissipation/kW Number Total heat dissipation/kW
ZK35 355.6 8 7637.5
ZK50 508.7 5
ZK60 606.4 2
ZK80 806.4 1
ZK25 230 1
Tab.3  Type and parameters of fan-coil unit terminals
Fig.3  Distribution of wells
Tp /°C ΔTgw /°C ηg /(m3·h-1) Ts /°C ΔTcw /°C ηc /(m3·h-1)
Average value 14–19 4–8 60–150 44 1.5–4.5 210–230
Design value 15 5 194 45 5 243
Tab.4  Actual measurements
Fig.4  Total energy consumption of GWHP system
Fig.5  Daily COP of system
Fig.6  Hourly COP of unit
Fig.7  Water temperature variations in a typical day
Fig.8  Simulation region
Fig.9  Simulation of pumping water temperature of Well 4
Fig.10  Pumping water temperature of Well 4
Fig.11  Frequency distribution of daily average outdoor temperature during heating season in a typical meteorological year
Fig.12  Relationship between building heat load and daily average outdoor temperature
Heat capacity/kW Input power/kW Temperatures of ground water loop/°C Temperatures of circulation water loop/°C
inlet outlet inlet outlet
1156.21 235.48 14.31 8.25 36.31 39.63
1165.75 237.91 14.38 8.44 37.31 40.63
1102.28 223.59 14.50 9.81 37.75 40.88
1137.81 227.56 14.50 8.31 36.81 40.06
1122.31 233.33 14.56 8.38 37.31 40.50
855.69 174.27 14.63 8.50 37.63 41.00
1267.50 247.08 14.88 8.38 36.06 39.69
1130.35 235.49 16.56 9.13 36.69 39.81
1110.51 227.56 17.31 8.94 36.81 39.56
1192.77 239.51 17.63 9.38 36.50 39.69
1171.89 236.27 18.13 9.50 35.75 38.50
1352.31 258.07 18.25 9.63 35.31 39.13
1158.10 238.78 18.31 9.81 34.75 37.88
Tab.5  Heat capacity and input power of GSHP units
Fig.13  Variation of building heat load and heat medium temperature when outdoor temperature changes
Aij i= 0 i= 1 i= 2
j= 0 0.9202 -0.01123 -0.003709
j= 1 -0.0062 -0.00073 -0.00054
j= 2 -0.00114 -0.00045 0.00035
Tab.6  Value of Aij
System load rate distribution Units load rate distribution
Φ≤0.33 PLR1 = 3Φ, PLR2 = PLR3 = 0
0.33<Φ≤0.67 PLR1 = PLR2 = 1.5Φ, PLR3 = 0
0.67<Φ≤1 PLR1 = PLR2 = PLR3 = Φ
Tab.7  Distribution of the load rate
Fig.14  H-Q and η-Q curve of circulation pumps
Fig.15  H-Q and η-Q curve of submersible pumps
Fig.16  Input powers of GWHP units at different outdoor temperatures
Fig.17  Input powers of GWHP units at different flow rates
Fig.18  Consumption of circulating pumps at different flow rates
Outdoor temperature/°C Number of units in operation COP of system Circulation water flow rate /(m3·h-1) Supply water temperature/°C Ground water flow rate/(m3·h-1) Reinjection water temperature/°C Total input power/kW
-12 3 4.66 420 55.56 130 14.92 1016.96
-11 3 4.48 400 54.15 130 14.92 1017.20
-10 3 4.30 450 52.73 130 14.92 1016.83
-9 3 4.13 450 51.31 130 14.92 1015.06
-8 3 3.97 450 49.90 130 14.92 1011.90
-7 3 3.81 430 48.48 130 14.92 1007.35
-6 3 3.66 400 47.06 130 14.92 1001.39
-5 3 3.50 380 45.65 130 14.92 994.05
-4 3 3.35 360 44.23 130 14.92 1005.62
-3 3 4.82 340 42.81 130 14.92 596.61
-2 3 4.60 420 41.40 130 14.92 589.55
-1 2 4.37 400 39.98 130 14.92 646.87
0 2 4.15 405 38.56 130 14.92 624.25
1 2 3.93 315 37.15 130 14.92 610.34
2 2 3.71 340 35.73 130 14.92 602.36
3 2 5.24 270 34.31 130 14.92 348.81
4 2 4.90 270 32.90 125 15.12 340.97
5 2 4.54 270 31.48 120 16.00 332.57
6 2 4.18 270 30.06 80 15.00 323.62
7 1 5.05 270 28.65 80 15.00 265.68
8 1 4.52 270 27.23 80 15.00 257.18
9 1 5.97 270 25.81 80 15.00 146.74
10 1 5.08 270 24.40 80 15.00 141.17
11 1 6.54 270 22.98 80 15.00 66.77
12 1 4.90 270 21.56 80 15.00 63.75
Tab.8  Operation modes and parameters at different outdoor temperatures
Fig.19  Temperature hour frequencies during the test
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