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

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Description

Grout is used to seal the annulus between the borehole and heat exchanger loops in vertical geothermal (ground coupled, ground source, GeoExchange) heat pump systems. The grout provides a heat transfer medium between the heat exchanger and surrounding formation, controls groundwater movement and prevents contamination of water supply. Enhanced heat pump coefficient of performance (COP) and reduced up-front loop installation costs can be achieved through optimization of the grout thermal conductivity. The objective of the work reported was to characterize thermal conductivity and other pertinent properties of conventional and filled cementitious grouts. Cost analysis and calculations of the reduction in ... continued below

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59 p.

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Allan, M. L. November 1997.

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Description

Grout is used to seal the annulus between the borehole and heat exchanger loops in vertical geothermal (ground coupled, ground source, GeoExchange) heat pump systems. The grout provides a heat transfer medium between the heat exchanger and surrounding formation, controls groundwater movement and prevents contamination of water supply. Enhanced heat pump coefficient of performance (COP) and reduced up-front loop installation costs can be achieved through optimization of the grout thermal conductivity. The objective of the work reported was to characterize thermal conductivity and other pertinent properties of conventional and filled cementitious grouts. Cost analysis and calculations of the reduction in heat exchanger length that could be achieved with such grouts were performed by the University of Alabama. Two strategies to enhance the thermal conductivity of cementitious grouts were used simultaneously. The first of these was to incorporate high thermal conductivity filler in the grout formulations. Based on previous tests (Allan and Kavanaugh, in preparation), silica sand was selected as a suitable filler. The second strategy was to reduce the water content of the grout mix. By lowering the water/cement ratio, the porosity of the hardened grout is decreased. This results in higher thermal conductivity. Lowering the water/cement ratio also improves such properties as permeability, strength, and durability. The addition of a liquid superplasticizer (high range water reducer) to the grout mixes enabled reduction of water/cement ratio while retaining pumpability. Superplasticizers are commonly used in the concrete and grouting industry to improve rheological properties.

Physical Description

59 p.

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OSTI as DE98002826

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  • Other Information: PBD: Nov 1997

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  • Other: DE98002826
  • Report No.: BNL--65129
  • Grant Number: AC02-76CH00016
  • DOI: 10.2172/573177 | External Link
  • Office of Scientific & Technical Information Report Number: 573177
  • Archival Resource Key: ark:/67531/metadc694819

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  • November 1997

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  • Aug. 14, 2015, 8:43 a.m.

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  • Nov. 13, 2015, 11:24 p.m.

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Allan, M. L. Thermal conductivity of cementitious grouts for geothermal heat pumps. Progress report FY 1997, report, November 1997; Upton, New York. (digital.library.unt.edu/ark:/67531/metadc694819/: accessed September 22, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.