Thermal conductivity of cementitious grouts for geothermal heat pumps. Progress report FY 1997

Allan, M.L.

doi:10.2172/573177

Cited by 24 publications

(22 citation statements)

References 7 publications

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“…After preparing mixtures constituted by materials commonly used as grouts, some particular thermal and mechanical tests were carried out [29]. One of these tests, that stands out because of its importance is the measuring "in situ" of the thermal conductivity parameter [30,31]. This property was determined by the thermal properties analyser commercially known as KD2 Pro developed by Decagon Devices [32].…”

Section: Grouting Materialsmentioning

confidence: 99%

Efficiency Analysis of the Main Components of a Vertical Closed-Loop System in a Borehole Heat Exchanger

et al. 2017

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Abstract:In vertical closed-loop systems, it is common to use single or double U-tube heat exchangers separated by longitudinal spacers. In addition, the helical-shaped pipe is another configuration that requires lower drilling lengths but it is less used. The aim of the present research is to study the influence of these components on the total efficiency of a borehole heat exchanger (BHE). Thus, the differences between using single/double U-tubes (with or without spacers) and helical pipes are analysed in terms of efficiency. Through different laboratory tests, a small vertical closed-loop system was simulated in order to analyse all these possible configurations. The grouting materials and the temperatures of the ground were modified at the same time in these tests. Regarding the heat exchange process between the ground and the heat carrier fluid, it must be highlighted that the best results were obtained for the helical-shaped pipe configuration. Some of the improvements offered by this heat exchanger typology with respect to the vertical configuration is that a lower drilling depth is required even it requires a larger diameter. This leads to significant economic savings in the performing drilling process. Finally, it is also worth noting the importance of using spacers in vertical U-tubes and that no improvements have been found regarding the use of single or double configuration of U-tubes. Thanks to the laboratory results derived from this study it is possible to establish the optimum behaviour pattern for the entire vertical closed-loop systems.

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Section: Grouting Materialsmentioning

confidence: 99%

Efficiency Analysis of the Main Components of a Vertical Closed-Loop System in a Borehole Heat Exchanger

et al. 2017

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“…The complete results for pH and concentrations of specific metals in deionized water in contact with the grouts in both the fresh and hardened states are reported elsewhere (Allan, 1997). It was determined that the leachability of elements fiom the grouts was below the EPA drinking water levels.…”

Section: Environmental Impactmentioning

confidence: 99%

“…This paper describes some of the major results to date. Further details of the research can be found in the FY 97 Progress Report (Allan, 1997).…”

Section: Introductionmentioning

confidence: 99%

Thermal conductivity and other properties of cementitious grouts

Allan¹

1998

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898 ~JJG 0The thermal conductivity and other properties cementitious grouts have been investigated in order to determine suitability of these materials for grouting vertical boreholes used with geothermal heat pumps. The roles of mix variables such as waterkement ratio, sandcement ratio and superplasticizer dosage were measured. In addition to thermal conductivity, the cementitious grouts were also tested for bleeding, permeability, bond to HDPE pipe, shrinkage, coefficient of thermal expansion, exotherm, durability and environmental impact. This paper summarizes the results for selected grout mixes. Relatively high thermal conductivities were obtained and this leads to reduction in predicted bore length and installation costs. Improvements in shrinkage resistance and bonding were achieved.

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“…In Sweden, Anna Gabrielsson [1] had monitored the UTES for three years, large vertical settlements appeared in the underground structure after two freeze/thaw cycles, which caused the unexpected buckling of pipe and resulted in a reduced flow in pipe. In the U.S.A., Marita Allan [2] developed the study of thermal stresses, deformations and thermal fractures of backfill material, which would influence the heat transfer. In Canada, Lenarduzzi Frank [3] announced the problem of vertical ground pipes squeeze in a GSHP project during the first heating season, at the same time, a series of model experiments were conducted to search for the cause of pipe squeeze.…”

Section: Introductionmentioning

confidence: 99%

The Study on Measuring Method of Heat Exchange Pipe Deformation and Displacement Based on Thermal Strain

Wang¹,

Gao²,

Xiao-lin³

et al. 2012

Proceedings of the 2nd International Conference on Electronic and Mechanical Engineering and Information Technology (2012)

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Thermal deformation of heat exchange pipe is the significant source of structural variation in ground heat exchange system, which could weaken the capability and reduce the reliability of heat transfer system after long-time operation. The experimental study of thermal deformation of heat exchange pipe should be carried out to explore its thermal behavior. The strain measuring method was applied to the study on thermal deformation and displacement, which was deduced from the measured strain in heat exchange pipe. The verifying experiment was carried out to analyse its feasibility in preliminary simulation environment. The result showed that strain measuring method is applicable and could be conducive to the deformation monitoring of heat exchange pipe in practical projects. IntroductionWith the rapid development and application of ground source heat pump and large temperature difference energy storage technology, the gradual performance degradation and even failure of ground heat exchange system were emerging, and also its reliability and durability have been paid more and more attention. Since the 1990s, many countries in Europe and America have carried out some preliminary study on these problems. In Sweden, Anna Gabrielsson [1] had monitored the UTES for three years, large vertical settlements appeared in the underground structure after two freeze/thaw cycles, which caused the unexpected buckling of pipe and resulted in a reduced flow in pipe. In the U.S.A., Marita Allan [2] developed the study of thermal stresses, deformations and thermal fractures of backfill material, which would influence the heat transfer. In Canada, Lenarduzzi Frank [3] announced the problem of vertical ground pipes squeeze in a GSHP project during the first heating season, at the same time, a series of model experiments were conducted to search for the cause of pipe squeeze. In Britain, Bourne [4] studied the temperature stress of heat exchanger piles and found that great temperature stress accumulation can lead to heat exchange structural failure.However,heat exchange pipe, as the most sensitive part to temperature, its deformation by temperature changes should be an important factor for the failure of ground heat exchange structure. Therefore, it is necessary to study the characteristics of pipe's thermal deformation firstly. The technology of strain measurement provides an effective means to develop this study

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Thermal conductivity of cementitious grouts for geothermal heat pumps. Progress report FY 1997

Cited by 24 publications

References 7 publications

Efficiency Analysis of the Main Components of a Vertical Closed-Loop System in a Borehole Heat Exchanger

Efficiency Analysis of the Main Components of a Vertical Closed-Loop System in a Borehole Heat Exchanger

Thermal conductivity and other properties of cementitious grouts

The Study on Measuring Method of Heat Exchange Pipe Deformation and Displacement Based on Thermal Strain

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