Ground Thermal Response and Recovery after Heat Injection: Experimental Investigation

Boban, Luka; Soldo, Vladimir; Stošić, Jura; Filipović, Eugen; Tremac, Filip

doi:10.21278/tof.42si104

Cited by 4 publications

(4 citation statements)

References 13 publications

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“…The ground thermal conductivity and borehole thermal resistance was determined by circulating heated fluid in a U-tube type BHE, while thermocouples placed on the borehole wall measured temperature profiles of undisrupted ground as well as during the recovery period. The analysis indicated that the true undisturbed state after rejected heat flux cannot be reached in short time while the use of higher rejection heat flux reduces the influence of the ground's inhomogeneity on the results obtained [4].…”

Section: Introduction and Literature Overviewmentioning

confidence: 94%

“…In order to evaluate the thermal response of heat rejection and recovery behaviour of the ground, two thermal response tests (TRT) were conducted on the same experimental borehole heat exchanger [4]. The testing consisted from two different heat pulses enforced to the same borehole, one with 4,43 kW and the other with 7,64 kW rejected heat flux.…”

Section: Introduction and Literature Overviewmentioning

confidence: 99%

See 1 more Smart Citation

Investigation of Steady-State Heat Extraction Rates for Different Borehole Heat Exchanger Configuration from the Aspect of Implementation of New TurboCollectorTM Pipe System Design

Kurevija¹,

Mehrjerdi²,

Macenić³

et al. 2019

Preprint

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When considering implementation of shallow geothermal energy as a renewable source for heating and cooling of the building, special care should be taken in hydraulic design of borehole heat exchanger system. Laminar flow can occur in pipes due to usage of glycol mixture at low temperature or inadequate flow rate. This can lead to lower heat extraction and rejection rates of the exchanger because of higher thermal resistances. Furthermore, by increasing flow rate to achieve turbulent flow and satisfactory heat transfer rate can lead to increase the pressure drop of the system and oversizing of circulation pump which leads to impairment of seasonal coefficient of performance at the heat pump. Most frequently used borehole heat exchanger system in Europe is double-loop pipe system with smooth inner wall. Lately, development is focused on implementation of different configuration as well as with ribbed inner wall which ensures turbulent flow in the system, even at lower flow rates. At a location in Zagreb, classical and extended thermal response test was conducted on three different heat exchanger configurations in the same geological environment. With classic TRT test, thermogeological properties of the ground and thermal resistance of the borehole were determined for each smooth or turbulator pipe configuration. Extended Steady-State Thermal Response Step Test (TRST) was implemented, which incorporate series of power steps to determine borehole extraction rate at the define steady-state heat transfer conditions of 0/-3°C. Results show that heat exchangers with ribbed inner pipe wall have advantages over classic double-loop smooth pipe design, in terms of greater steady state heat extraction rate and more favorable hydraulic conditions.

show abstract

Section: Introduction and Literature Overviewmentioning

confidence: 94%

Section: Introduction and Literature Overviewmentioning

confidence: 99%

Investigation of Steady-State Heat Extraction Rates for Different Borehole Heat Exchanger Configuration from the Aspect of Implementation of New TurboCollectorTM Pipe System Design

Kurevija¹,

Mehrjerdi²,

Macenić³

et al. 2019

Preprint

View full text Add to dashboard Cite

show abstract

“…In the last decade alone there has been a rise of research when it comes to optimizing the BHE system, by observing the influence of various geometrical settings, hydraulic settings and heat rates on the overall performance. Various studies have focused on a better understanding and more precise estimation of effective thermal conductivity and borehole thermal resistance [1][2][3][4] as important parameters when exploiting the shallow geothermal resource. Current methods of determining the average fluid temperature within BHE, as well as the influence of various measuring methods during TRT, on the final determination of thermal properties are also available [5][6][7].…”

Section: Introduction and Literature Overviewmentioning

confidence: 99%

“…The origin of both procedures lies in the same diffusivity differential equation, with solutions for heat conduction or pressure transient analysis during radial flow in porous media. The use of the step thermal response test showed that it is suitable when determining heat rejection/extraction rates, useful for design optimization of the BHE field [3,10]. The influence of the groundwater advection on the efficiency and modelling of the ground BHE is detailed, with the study of its relationship with the modeling of the BHE field [7,[11][12][13].…”

Section: Introduction and Literature Overviewmentioning

confidence: 99%

Investigation of Steady-State Heat Extraction Rates for Different Borehole Heat Exchanger Configurations from the Aspect of Implementation of New TurboCollector™ Pipe System Design

et al. 2019

View full text Add to dashboard Cite

When considering implementation of shallow geothermal energy as a renewable source for heating and cooling of buildings, special care should be taken in the hydraulic design of the borehole heat exchanger system. Laminar flow can occur in pipes due to the usage of glycol mixtures at low temperature or inadequate flow rates. This can lead to lower heat extraction and rejection rates of the exchanger because of higher thermal resistance. Furthermore, by increasing the flow rate to achieve turbulent flow and satisfactory heat transfer rate can lead to an increase in the pressure drop of the system and oversizing of the circulation pump which leads to impairment of the seasonal coefficient of performance at the heat pump. The most frequently used borehole heat exchanger system in Europe is a double-loop pipe system with a smooth inner wall. Lately, development is focused on the implementation of a different configuration as well as with ribbed inner walls which ensures turbulent flow in the system, even at lower flow rates. At a location in Zagreb, standard and extended thermal response tests were conducted on three different heat exchanger configurations in the same geological environment. With a standard TRT test, thermogeological properties of the ground and thermal resistance of the borehole were determined for each smooth or turbulator pipe configuration. On the other hand, extended Steady-State Thermal Response Step Test (TRST) incorporates a series of power steps to determine borehole extraction rates at the defined steady-state heat transfer conditions of 0/–3 °C. When comparing most common exchanger, 2U-loop D32 smooth pipe, with novel 1U-loop D45 ribbed pipe, an increase in heat extraction of 6.5% can be observed. Also, when the same comparison is made with novel 2U-loop D32 ribbed pipe, an increase of 18.7% is achieved. Overall results show that heat exchangers with ribbed inner pipe wall have advantages over classic double-loop smooth pipe designs, in terms of greater steady-state heat extraction rate and more favorable hydraulic conditions.

show abstract

Improving thermal response tests with wireline temperature logs to evaluate ground thermal conductivity profiles and groundwater fluxes

2019

View full text Add to dashboard Cite

Ground Thermal Response and Recovery after Heat Injection: Experimental Investigation

Cited by 4 publications

References 13 publications

Investigation of Steady-State Heat Extraction Rates for Different Borehole Heat Exchanger Configuration from the Aspect of Implementation of New TurboCollectorTM Pipe System Design

Investigation of Steady-State Heat Extraction Rates for Different Borehole Heat Exchanger Configuration from the Aspect of Implementation of New TurboCollectorTM Pipe System Design

Investigation of Steady-State Heat Extraction Rates for Different Borehole Heat Exchanger Configurations from the Aspect of Implementation of New TurboCollector™ Pipe System Design

Improving thermal response tests with wireline temperature logs to evaluate ground thermal conductivity profiles and groundwater fluxes

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