scholarly journals Effect of groundwater forced seepage on heat transfer characteristics of borehole heat exchangers

2020 ◽  
Author(s):  
Jiuchen Ma ◽  
Qian Jiang ◽  
Qiuli Zhang ◽  
Yacheng Xie ◽  
Yahui Wang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Exchangers ◽  
Flow Volume ◽  
Transfer Rates ◽  
Average Heat ◽  
Cooling Stage ◽  
Heating Stage ◽  
Injection Flow ◽  
Borehole Heat Exchangers

Abstract A borehole heat exchangers (BHEs) combined with pumping-injection well is established in areas where groundwater is shallow but the seepage velocity is weak, which sets up pumping and injection wells on both sides of the BHEs. According to the three-dimensional unsteady state heat transfer model in aquifer, we derive the convection-dispersion analytical solution of excess temperature in aquifer that considers groundwater forced seepage and thermal dispersion effects in aquifer and the axial effect of the BHEs. Then, we use dimensional analysis method and similarity criteria to build a controllable forced seepage sandbox. The theoretical analysis is combined with the indoor experiment test to verify the correctness and accuracy of the numerical simulation software FEFLOW7.1. On this basis, we perform the numerical simulation calculation to explore the effects of different pumping-injection flow volume on the Darcy flow velocity of the aquifer where the BHEs are located, the average heat transfer efficiency and the heat transfer rates per unit borehole depth of the BHEs. The results show that when the pumping flow volume is increased from 200 m3∙d-1 to 1200 m3∙d-1, the Darcy velocity correspondingly increases to about 10 times the previous velocity. The average heat efficiency coefficient of the BHEs increases by 11.5% in cooling stage, and by 7.5% in heating stage. When the pumping-injection flow volume is 400~600 m3∙d-1, the increment of heat transfer rates per unit borehole depth of the BHEs reaches 12.8~17.9 W∙m-1 and 3.6~4.2 W∙m-1 during the cooling stage and heating stage respectively, and then decreases as the flow volume increases gradually.

scholarly journals Effect of groundwater forced seepage on heat transfer characteristics of borehole heat exchangers

2021 ◽  
Author(s):  
Jiuchen Ma ◽  
Qian Jiang ◽  
Qiuli Zhang ◽  
Yacheng Xie ◽  
Yahui Wang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Similarity Criteria ◽  
Flow Volume ◽  
Transfer Rates ◽  
Average Heat ◽  
Cooling Stage ◽  
Heating Stage ◽  
Injection Flow ◽  
Borehole Heat Exchangers

Abstract A borehole heat exchangers (BHEs) combined with pumping-injection well is established in areas where the groundwater is shallow and the seepage velocity is weak. The pumping and injection wells are set on both sides of the BHEs. According to the three-dimensional unsteady heat transfer model in aquifer, the convection-dispersion analytical solution of excess temperature is derived that considers groundwater forced seepage and thermal dispersion effects and axial effect of the BHEs. Then, the dimensional analysis method and similarity criteria we used to build a controllable forced seepage sandbox. The software FEFLOW 7.1 is adopted and the simulation results are validated by the theoretical analysis and the indoor experiment test. On this basis, the numerical simulation calculation is used to explore the influence of different pumping-injection flow volume on the Darcy flow velocity of the aquifer where the BHEs are located, the average heat transfer efficiency and the heat transfer rates with borehole depth. The results show that when the pumping flow volume increases from 200 m3∙d-1 to 1200 m3∙d-1, the Darcy velocity correspondingly increases to about 10 times. The average heat efficiency coefficient of the BHEs is increased by 11.5% in cooling stage, and by 7.5% in heating stage. When the pumping-injection flow volume is 400~600 m3∙d-1, the increment of heat transfer rates of the BHEs reaches 12.8~17.9 W∙m-1 and 3.6~4.2 W∙m-1 per unit of borehole depth during the cooling stage and heating stage respectively, and then decreases as the flow volume increases gradually.

scholarly journals Effect of groundwater forced seepage on heat transfer characteristics of borehole heat exchangers

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Jiuchen Ma ◽  
Qian Jiang ◽  
Qiuli Zhang ◽  
Yacheng Xie ◽  
Yahui Wang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Flow Volume ◽  
Injection Wells ◽  
Transfer Rates ◽  
Average Heat ◽  
Cooling Stage ◽  
Heating Stage ◽  
Injection Flow ◽  
Borehole Heat Exchangers

AbstractA system of borehole heat exchangers (BHEs) combined with pumping–injection wells is established in areas where the groundwater is shallow and the seepage velocity is weak. The pumping and injection wells are set on both sides of the BHEs. According to the three-dimensional unsteady-state heat transfer model in the aquifer, the convection–dispersion analytical solution of excess temperature is derived that considers groundwater-forced seepage and thermal dispersion effects and axial effect of the BHEs. Then, we use the dimensional analysis method and similarity criteria to build a controllable forced seepage sandbox. The software FEFLOW 7.1 is adopted and the simulation results are validated by the theoretical analysis and the indoor experiment test. On this basis, the numerical simulation is used to explore the influence of different pumping–injection flow volume on the Darcy flow velocity of the aquifer where the BHEs are located, as well as the average heat transfer efficiency and the heat transfer rates with borehole depth. The results show that when the pumping flow volume increases from 200 m3 day−1 to 1200 m3 day−1, the Darcy velocity correspondingly increases to about 10 times. The average heat efficiency coefficient of the BHEs is increased by 11.5% in cooling stage, and by 7.5% in heating stage. When the pumping–injection flow volume is 400–600 m3 day−1, the increment of heat transfer rates of the BHEs reaches 12.8–17.9 W m−1 and 3.6–4.2 W m−1 per unit of borehole depth during the cooling stage and heating stage, respectively, and then decreases as the flow volume increases gradually.

scholarly journals Execution of a Smart Prediction Tool to Evaluate Thermal Performance in a heat exchanger by using Single Elliptical Leaf Strips with altered Angle

2019 ◽  
Vol 8 (11) ◽  
pp. 123-131
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Thermal Performance ◽  
Heat Exchangers ◽  
Industrial Applications ◽  
Generalized Regression Neural Network ◽  
Prediction Tool ◽  
Pressure Drops ◽  
Transfer Rates ◽  
Mass Flow Rates

Heat exchangers are prominent industrial applications where engineering science of heat transfer and Mass transfer occurs. It is a contrivance where transfer of energy occurs to get output in the form of energy transfer. This paper aims at finding a solution to improve the thermal performance in a heat exchanger by using passive method techniques. This experimental and numerical analysis deals with finding the temperature outlets of cold and hot fluid for different mass flow rates and also pressure drop in the tube and the annular side by adding an elliptical leaf strip in the pipe at various angles. The single elliptical leaf used in experiment has major to minor axes ratios as 2:1 and distance of 50 mm between two leaves are arranged at different angular orientations from 0 0 to 1800 with 100 intervals. Since it’s not possible to find the heat transfer rates and pressure drops at every orientation of elliptical leaf so a generalized regression neural network (GRNN) prediction tool is used to get outputs with given inputs to avoid experimentation. GRNN is a statistical method of determining the relationship between dependent and independent variables. The values obtained from experimentation and GRNN nearly had precise values to each other. This analysis is a small step in regard with encomiastic approach for enhancement in performance of heat exchangers

scholarly journals Effect of the size of graded baffles on the performance of channel heat exchangers

2020 ◽  
Vol 24 (2 Part A) ◽  
pp. 767-775 ◽  
Author(s):  
Djamel Sahel ◽  
Houari Ameur ◽  
Touhami Baki
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Exchangers ◽  
Computer Code ◽  
Channel Length ◽  
Heat Transfer Characteristics ◽  
Enhancement Of Heat Transfer ◽  
Transfer Rates ◽  
Flow And Heat Transfer ◽  
Friction Factors

The baffling technique is well-known for its efficiency in terms of enhancement of heat transfer rates throught channels. However, the baffles insert is accompanied by an increase in the friction factor. This issue remains a great challenge for the designers of heat exchangers. To overcome this issue, we suggest in the present paper a new design of baffles which is here called graded baffle-design. The baffles have an up- or down-graded height along the channel length. This geometry is characterized by two ratios: up-graded baffle ratio and down-graded baffle ratio which are varied from 0-0.08. For a range of Reynolds number varying from 104 to 2 ? 104, the turbulent flow and heat transfer characteristics of a heat exchanger channel are numerically studied by the computer code FLUENT. The obtained results revealed an enhancement in the thermohydraulic performance offered by the new suggested design. For the channel with a down-graded baffle ratio equal to 0.08, the friction factors decreased by 4-8%

Numerical Simulation and Optimization of Radial Heat Pipe Heat Exchanger Based on Field Synergy Principle

2013 ◽  
Vol 834-836 ◽  
pp. 1418-1422
Author(s):  
Qing Yun Liu ◽  
Fu Bing Tu ◽  
Sheng Yang Gao
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Transfer Coefficient ◽  
Heat Exchangers ◽  
Synergy Effect ◽  
Field Synergy ◽  
Field Synergy Principle ◽  
Radial Heat ◽  
The Heat Transfer Coefficient ◽  
Pipe Heat

This paper mainly explores the numerical simulation of flow and temperature fields in the shell-side of the radial heat pipe heat exchangers (HPHE), using CFD software-FLUENT. Field synergy principle is applied to analyze heat and mass transfer mechanism of heat exchangers; also, the influence of the variation of principle constructor parameters of heat exchangers on the field synergy effect and heat exchange performance has been studied. It has been found that better performance of heat exchangers is achieved with better field synergy effect; in the context of increasing transverse and longitudinal tube pitches within certain values of data, the heat transfer coefficient decreases as synergy angle increases. Variation of fin height has little effect on synergy angle, but it would decrease the heat transfer coefficient at unit pressure drop (k/Δp) as it increases; as fin pitch increases, the synergy angle first decreases and then grows, while k/Δp first increases and then decreases. The optimal ranges of heat exchanger structure parameters values were found.

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