scholarly journals Prediction and parametric analysis of 3D borehole and total internal thermal resistance of single U-tube borehole heat exchanger for ground source heat pumps

2021 ◽  
Author(s):  
Kun Zhou ◽  
Jinfeng Mao ◽  
Yong Li ◽  
Hua Zhang ◽  
Zhongkai Deng
Keyword(s):  
Heat Exchanger ◽  
Thermal Resistance ◽  
Parametric Analysis ◽  
Heat Pumps ◽  
Borehole Heat Exchanger ◽  
Ground Source Heat Pumps ◽  
Ground Source ◽  
Internal Thermal Resistance

scholarly journals Field Test and Numerical Simulation on Heat Transfer Performance of Coaxial Borehole Heat Exchanger

Energies ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 5471
Author(s):  
Peng Li ◽  
Peng Guan ◽  
Jun Zheng ◽  
Bin Dou ◽  
Hong Tian ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Properties ◽  
Heat Exchanger ◽  
Flow Rate ◽  
Thermal Response ◽  
Heat Pumps ◽  
Inlet Temperature ◽  
Borehole Heat Exchanger ◽  
Ground Source Heat Pumps ◽  
Ground Source

Ground thermal properties are the design basis of ground source heat pumps (GSHP). However, effective ground thermal properties cannot be obtained through the traditional thermal response test (TRT) method when it is used in the coaxial borehole heat exchanger (CBHE). In this paper, an improved TRT (ITRT) method for CBHE is proposed, and the field ITRT, based on the actual project, is carried out. The high accuracy of the new method is verified by laboratory experiments. Based on the results of the ITRT and laboratory experiment, the 3D numerical model for CBHE is established, in which the flow directions, sensitivity analysis of heat transfer characteristics, and optimization of circulation flow rate are studied, respectively. The results show that CBHE should adopt the anulus-in direction under the cooling condition, and the center-in direction under the heating condition. The influence of inlet temperature and flow rate on heat transfer rate is more significant than that of the backfill grout material, thermal conductivity of the inner pipe, and borehole depth. The circulating flow rate of CBHE between 0.3 m/s and 0.4 m/s can lead to better performance for the system.

scholarly journals Connecting Dynamic Heat Demands of Buildings with Borehole Heat Exchanger Simulations for Realistic Monitoring and Forecast

2021 ◽  
Vol 56 ◽  
pp. 45-56
Author(s):  
Jan Niederau ◽  
Johanna Fink ◽  
Moritz Lauster
Keyword(s):  
Heat Exchanger ◽  
Groundwater Flow ◽  
Energy Demand ◽  
Average Energy ◽  
Time Frame ◽  
Heat Pumps ◽  
Borehole Heat Exchanger ◽  
Ground Source Heat Pumps ◽  
Private Households ◽  
Average Energy Consumption

Abstract. Space heating is a major contributor to the average energy consumption of private households, where the energy standard of a building is a controlling parameter for its heating energy demand. Vertical Ground Source Heat Pumps (vGSHP) present one possibility for a low-emission heating solution. In this paper, we present results of building performance simulations (BPS) coupled with vGSHP simulations for modelling the response of vGSHP-fields to varying heating power demands, i.e. different building types. Based on multi-year outdoor temperature data, our simulation results show that the cooling effect of the vGSHPs in the subsurface is about 2 K lower for retrofitted buildings. Further, a layout with one borehole heat exchanger per building can be efficiently operated over a time frame of 15 years, even if the vGSHP-field layout is parallel to regional groundwater flow in the reservoir body. Due to northward groundwater flow, thermal plumes of reduced temperatures develop at each vGSHP, showing that vGSHPs in the southern part of the model affect their northern neighbors. Considering groundwater flow in designing the layout of the vGSHP-field is conclusively important. Combining realistic estimates of the energy demand of buildings by BPS with subsurface reservoir simulations thus presents a tool for monitoring and managing the temperature field of the subsurface, affected by Borehole Heat Exchanger (BHE) installations.

Application of Artificial Neural Networks to Predict Heat Transfer From Buried Pipe for Ground Source Heat Pump Applications

2013 ◽  
Author(s):  
Hakan Demir ◽  
Ş. Özgür Atayılmaz ◽  
Özden Agra ◽  
Ahmet Selim Dalkılıç
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Numerical Study ◽  
Energy Resource ◽  
Heat Pumps ◽  
Burial Depth ◽  
Buried Pipe ◽  
Ground Source Heat Pumps ◽  
Ground Source ◽  
Artificial Neural

The earth is an energy resource which has more suitable and stable temperatures than air. Ground Source Heat Pumps (GSHPs) were developed to use ground energy for residential heating. The most important part of a GSHP is the Ground Heat Exchanger (GHE) that consists of pipes buried in the soil and is used for transferring heat between the soil and the heat exchanger of the GSHP. Soil composition, density, moisture and burial depth of pipes affect the size of a GHE. Design of GSHP systems in different regions of US and Europe is performed using data from an experimental model. However, there are many more techniques including some complex calculations for sizing GHEs. An experimental study was carried out to investigate heat transfer in soil. A three-layer network is used for predicting heat transfer from a buried pipe. Measured fluid inlet temperatures were used in the artificial neural network model and the fluid outlet temperatures were obtained. The number of the neurons in the hidden layer was determined by a trial and error process together with cross-validation of the experimental data taken from literature evaluating the performance of the network and standard sensitivity analysis. Also, the results of the trained network were compared with the numerical study.

scholarly journals Different Approaches for Evaluation and Modeling of the Effective Thermal Resistance of Groundwater-Filled Boreholes

Energies ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6908
Author(s):  
Oleg Todorov ◽  
Kari Alanne ◽  
Markku Virtanen ◽  
Risto Kosonen
Keyword(s):  
Thermal Resistance ◽  
Heat Pumps ◽  
Fluid Temperature ◽  
Distributed Temperature Sensing ◽  
Ground Source Heat Pumps ◽  
Groundwater Levels ◽  
Common Solution ◽  
Ground Source ◽  
Geological Conditions

Groundwater-filled boreholes are a common solution in Scandinavian installations of ground source heat pumps (GSHP) due to the particular hydro-geological conditions with existing bedrock, and groundwater levels close to the surface. Different studies have highlighted the advantage of water-filled boreholes compared with their grouted counterparts since the natural convection of water within the borehole tends to decrease the effective thermal resistance Rb*. In this study, several methods are proposed for the evaluation and modeling of the effective thermal resistance of groundwater-filled boreholes. They are based on distributed temperature sensing (DTS) measurements of six representative boreholes within the irregular 74-single-U 300 m-deep borehole field of Aalto New Campus Complex (ANCC). These methods are compared with the recently developed correlations for groundwater-filled boreholes, which are implemented within the python-based simulation toolbox Pygfunction. The results from the enhanced Pygfunction simulation with daily update of Rb* show very good agreement with the measured mean fluid temperature of the first 39 months of system operation (March 2018–May 2021). It is observed that in real operation the effective thermal resistance Rb* can vary significantly, and therefore it is concluded that the update of Rb* is crucial for a reliable long-term simulation of groundwater-filled boreholes.

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