The Long-Term Mitigating Effect of Horizontal Ground-Source Heat Exchangers on Permafrost Thaw Settlement

This study investigated the long-term effect of horizontal Ground-Source Heat Exchangers (GSHEs) on mitigating permafrost thaw settlement. In the conceptual system, a fan coil was used to chill the recirculating fluid in the linear High-Density Polyethylene (HDPE) ground loop system. A fully coupled thermo-hydro-mechanical finite element framework was employed to analyze multiphysics processes involved in the thaw settlement phenomenon. To investigate the sustainability of the system, a period of 50 years was simulated. Two operational modes were defined: one without and the other with HDPE. Different heat carrier velocities and inlet temperatures, and heat exchanger depths were examined to explore their effects on the thaw settlement rate. It was concluded that the proposed system can effectively alleviate the predicted permafrost thaw settlement over the study period. Moreover, the heat carrier temperature was found to have a prominent impact on the thaw settlement rate amongst other parameters.

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Long-term effect of biochar application on yield-scaled greenhouse gas emissions in a rice paddy cropping system: A four-year case study in south China

The Science of The Total Environment ◽

10.1016/j.scitotenv.2016.06.222 ◽

2016 ◽

Vol 569-570 ◽

pp. 1390-1401 ◽

Cited By ~ 42

Author(s):

Xiaobo Qin ◽

Yu'e Li ◽

Hong Wang ◽

Chong Liu ◽

Jianling Li ◽

...

Keyword(s):

Greenhouse Gas Emissions ◽

Greenhouse Gas ◽

South China ◽

Cropping System ◽

Rice Paddy ◽

Term Effect ◽

System A ◽

Long Term Effect

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Nanofluid suspensions as heat carrier fluids in single U-tube borehole heat exchangers

Journal of Physics Conference Series ◽

10.1088/1742-6596/2116/1/012100 ◽

2021 ◽

Vol 2116 (1) ◽

pp. 012100

Author(s):

A Jahanbin ◽

G Semprini ◽

B Pulvirenti

Keyword(s):

Thermal Resistance ◽

Heat Carrier ◽

Thermal Performance ◽

Heat Exchangers ◽

Borehole Heat Exchanger ◽

Carrier Fluid ◽

Improve Energy Efficiency ◽

Ground Source ◽

Borehole Thermal Resistance ◽

Borehole Heat Exchangers

Abstract The borehole heat exchanger (BHE) is a critical component to improve energy efficiency and decreasing environmental impact of ground-source heat pump systems. The lower thermal resistance of the BHE results in the better thermal performance and/or in the lower required borehole length. In the present study, effects of employing a nanofluid suspension as a heat carrier fluid on the borehole thermal resistance are examined. A 3D transient finite element code is adopted to evaluate thermal comportment of nanofluids with various concentrations in single U-tube borehole heat exchangers and to compare their performance with the conventional circuit fluid. The results show, in presence of nanoparticles, the borehole thermal resistance is reduced to some extent and the BHE renders a better thermal performance. It is also revealed that employing nanoparticle fractions between 0.5% and 2 % are advantageous in order to have an optimal decrement percentage of the thermal resistance.

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It Works—Long-Term Performance Measurement and Optimization of Six Ground Source Heat Pump Systems in Germany

Energies ◽

10.3390/en12244691 ◽

2019 ◽

Vol 12 (24) ◽

pp. 4691 ◽

Cited By ~ 3

Author(s):

Franziska Bockelmann ◽

M. Norbert Fisch

Keyword(s):

Heat Pump ◽

Heat Exchangers ◽

Control Strategies ◽

Ground Source Heat Pump ◽

Cooling Systems ◽

Heating And Cooling ◽

Ground Source ◽

And Performance ◽

Term Performance

Long-term studies of ground source heat pump (GSHP) heating and cooling systems for six different buildings (commercial, institutional and multi-family buildings) were conducted in Germany by Steinbeis-Innovationszentrum (SIZ) energy+. Three of them are equipped with borehole heat exchangers, and the others use energy piles as heat exchangers. This paper deals with a demonstration of the investigated buildings, the measured values and performance, and the obtained results include important findings and experiences, problems encountered and possible preventive measures to avoid mistakes. After ten years of operation, it can be stated that the systems work and achieve their planned efficiency but require constant control and regulation to avoid faulty operation. An analysis of the implemented control strategies shows that, for all these heating and cooling systems, holistically coordinated control strategies that are verified during commissioning are required.

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Finite Element Modeling of Geothermal Source of Heat Pump in Long-Term Operation

Energies ◽

10.3390/en13061341 ◽

2020 ◽

Vol 13 (6) ◽

pp. 1341 ◽

Cited By ~ 2

Author(s):

Elżbieta Hałaj ◽

Leszek Pająk ◽

Bartosz Papiernik

Keyword(s):

Heat Pump ◽

Thermal Energy ◽

Heat Exchangers ◽

Thermal Recovery ◽

Small Scale ◽

Term Operation ◽

Ground Source ◽

Space Cooling ◽

Borehole Heat Exchangers

Model simulation allows to present the time-varying temperature distribution of the ground source for heat pumps. A system of 25 double U-shape borehole heat exchangers (BHEs) in long-term operation and three scenarios were created. In these scenarios, the difference between balanced and non-balanced energy load was considered as well as the influence of the hydrogeological factors on the temperature of the ground source. The aim of the study was to compare different thermal regimes of BHEs operation and examine the influence of small-scale and short-time thermal energy storage on ground source thermal balance. To present the performance of the system according to geological and hydrogeological factors, a Feflow® software (MIKE Powered by DHI Software) was used. The temperature for the scenarios was visualized after 10 and 30 years of the system’s operation. In this paper, a case is presented in which waste thermal energy from space cooling applications during summer months was used to upgrade thermal performance of the ground (geothermal) source of a heat pump. The study shows differences in the temperature in the ground around different Borehole Heat Exchangers. The cold plume from the not-balanced energy scenario is the most developed and might influence the future installations in the vicinity. Moreover, seasonal storage can partially overcome the negative influence of the travel of a cold plume. The most exposed to freezing were BHEs located in the core of the cold plumes. Moreover, the influence of the groundwater flow on the thermal recovery of the several BHEs is visible. The proper energy load of the geothermal source heat pump installation is crucial and it can benefit from small-scale storage. After 30 years of operation, the minimum average temperature at 50 m depth in the system with waste heat from space cooling was 2.1 °C higher than in the system without storage and 1.6 °C higher than in the layered model in which storage was not applied.

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