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.

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 Study on the Coupled Heat Transfer Model Based on Groundwater Advection and Axial Heat Conduction for the Double U-Tube Vertical Borehole Heat Exchanger

2020 ◽  
Vol 12 (18) ◽  
pp. 7345
Author(s):  
Linlin Zhang ◽  
Zhonghua Shi ◽  
Tianhao Yuan
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Transfer Rate ◽  
Flow Rate ◽  
Transfer Rate ◽  
Heat Transfer Model ◽  
Transfer Model ◽  
Borehole Heat Exchanger ◽  
Coupled Heat Transfer ◽  
Advection Velocity

In this paper, a dynamic heat transfer model for the vertical double U-tube borehole heat exchanger (BHE) was developed to comprehensively address the coupled heat transfer between the in-tube fluid and the soil with groundwater advection. A new concept of the heat transfer effectiveness was also proposed to evaluate the BHE heat exchange performance together with the index of the heat transfer rate. The moving finite line heat source model was selected for heat transfer outside the borehole and the steady-state model for inside the borehole. The data obtained in an on-site thermal response test were used to validate the physical model of the BHE. Then, the effects of soil type, groundwater advection velocity, inlet water flow rate, and temperature on the outlet water temperature of BHE were explored. Results show that ignoring the effects of groundwater advection in sand gravel may lead to deviation in the heat transfer rate of up to 38.9% of the ground loop design. The groundwater advection fosters the heat transfer of BHE. An increase in advection velocity may also help to shorten the time which takes the surrounding soil to reach a stable temperature. The mass flow rate of the inlet water to the BHE should be more than 0.5 kg·s−1 but should not exceed a certain upper limit under the practical engineering applications with common scale BHE. The efficiency of the heat transfer of the double U-tube BHE was determined jointly by factors such as the soil’s physical properties and the groundwater advection velocity.

Thermal Performance of a Borehole Heat Exchanger Located in Guayaquil-Ecuador Using Novel Heat Transfer Fluids

2015 ◽  
Author(s):  
Guillermo Soriano ◽  
Diego Siguenza
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Thermal Performance ◽  
Phase Change Materials ◽  
Three Dimensional ◽  
Borehole Heat Exchanger ◽  
Element Analysis ◽  
Heat Transfer Fluids ◽  
Ground Source ◽  
Microencapsulated Phase Change Materials

An analysis of thermal performance of a vertical Borehole Heat Exchanger (BHE) from a close loop Ground Source Heat Pump (GSHP) located in Guayaquil-Ecuador is presented. The project aims to assess the influence of using novels heat transfer fluids such as nanofluids, slurries with microencapsulated phase change materials and a mixture of both. The BHEs sensitive evaluation is performed by a mathematical model in a finite element analysis by using computational tools; where, the piping array is studied in one dimension scenario meanwhile its surroundings grout and ground volumes are presented as a three dimensional scheme. Therefore, an optimized model design can be achieved which would allow to study the feasibility of GSHP in buildings and industries in Guayaquil-Ecuador.

Study on Engineering Construction with Three-Dimensional Heat Transfer Modeling for Double U-Tube Heat Exchangers in Ground-Source Heat Pump Systems

2013 ◽  
Vol 700 ◽  
pp. 231-234
Author(s):  
Lian Yang ◽  
Yong Hong Huang ◽  
Liu Zhang
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Pump ◽  
Heat Exchangers ◽  
Three Dimensional ◽  
Ground Source Heat Pump ◽  
Ground Source Heat Pumps ◽  
Engineering Construction ◽  
Single Hole ◽  
Ground Source

There are many ground source heat pumps in engineering construction application. However, Research on heat exchanger models of single-hole buried vertical ground source heat pump mostly focuses on single U-tube ground heat exchangers other than double U-tube ones in China currently. Compared with single U-tubes, double U-tubes have the heat transfer particularity of asymmetry. Therefore, the use of the traditional single tube models would have large error in the simulation of the actual double U-tube heat exchangers. This paper frames a three-dimensional heat transfer model for the vertical single-hole buried double u-tube heat exchanger in a ground source heat pump system. The model considers the performance of U-bube material and uses a dual coordinate system and makes the control elemental volumes superimposed.

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.

On Fluid Flow and Heat Transfer in a Pipe With a U-Bend

2013 ◽  
Author(s):  
Christopher G. Cvetkovski ◽  
Hoda S. Mozaffari ◽  
Stanley Reitsma ◽  
Tirupati Bolisetti ◽  
David S.-K. Ting
Keyword(s):  
Heat Transfer ◽  
Flow Characteristics ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Heat Pumps ◽  
Heat Transfer Fluid ◽  
Heated Wall ◽  
Dean Number ◽  
Ground Source Heat Pumps ◽  
Ground Source

Vertical ground source heat pumps operate by pumping a heat transfer fluid through a pipe buried in the ground. There is a U-Bend at its deepest point to return the fluid to the surface. Incidentally, the U-Bend does more than packing the extensive length of the heat transferring conduit within a single compact borehole. Large flow structures called Dean’s vortices are generated in the bend and these, along with the resulting turbulence produced, are known to significantly enhance the heat transfer processes, and hence, shorten the required length. This study examines the specific roles of Reynolds and Dean numbers on the flow structure and the resulting heat transfer in a pipe with a U-Bend. Water flowing in a pipe without and with heated wall was simulated using FLUENT. The model was verified based on available data in the literature. The efficacy of the local heat transfer rate along the pipe was cast with respect to the subtle changes in the flow characteristics under varying Reynolds number and Dean number.

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