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Title: Thermally conductive cementitious grout for geothermal heat pump systems

Abstract

A thermally conductive cement-sand grout for use with a geothermal heat pump system. The cement sand grout contains cement, silica sand, a superplasticizer, water and optionally bentonite. The present invention also includes a method of filling boreholes used for geothermal heat pump systems with the thermally conductive cement-sand grout. The cement-sand grout has improved thermal conductivity over neat cement and bentonite grouts, which allows shallower bore holes to be used to provide an equivalent heat transfer capacity. In addition, the cement-sand grouts of the present invention also provide improved bond strengths and decreased permeabilities. The cement-sand grouts can also contain blast furnace slag, fly ash, a thermoplastic air entraining agent, latex, a shrinkage reducing admixture, calcium oxide and combinations thereof.

Inventors:
 [1]
  1. (Old Field, NY)
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL), Upton, NY
OSTI Identifier:
873806
Patent Number(s):
US 6251179
Assignee:
United States of America as represented by Department of Energy (Washington, DC) BNL
DOE Contract Number:
AC02-98C1110886
Resource Type:
Patent
Country of Publication:
United States
Language:
English
Subject:
thermally; conductive; cementitious; grout; geothermal; heat; pump; systems; cement-sand; cement; sand; contains; silica; superplasticizer; water; optionally; bentonite; method; filling; boreholes; improved; thermal; conductivity; neat; grouts; allows; shallower; bore; holes; provide; equivalent; transfer; capacity; addition; bond; strengths; decreased; permeabilities; contain; blast; furnace; slag; fly; ash; thermoplastic; air; entraining; agent; latex; shrinkage; reducing; admixture; calcium; oxide; combinations; pump systems; bore holes; cementitious grout; provide improved; improved thermal; calcium oxide; thermal conductivity; fly ash; heat pump; heat transfer; thermally conductive; silica sand; geothermal heat; thermal heat; sand grout; provide improve; blast furnace; bond strength; /106/166/507/

Citation Formats

Allan, Marita. Thermally conductive cementitious grout for geothermal heat pump systems. United States: N. p., 2001. Web.
Allan, Marita. Thermally conductive cementitious grout for geothermal heat pump systems. United States.
Allan, Marita. Mon . "Thermally conductive cementitious grout for geothermal heat pump systems". United States. doi:. https://www.osti.gov/servlets/purl/873806.
@article{osti_873806,
title = {Thermally conductive cementitious grout for geothermal heat pump systems},
author = {Allan, Marita},
abstractNote = {A thermally conductive cement-sand grout for use with a geothermal heat pump system. The cement sand grout contains cement, silica sand, a superplasticizer, water and optionally bentonite. The present invention also includes a method of filling boreholes used for geothermal heat pump systems with the thermally conductive cement-sand grout. The cement-sand grout has improved thermal conductivity over neat cement and bentonite grouts, which allows shallower bore holes to be used to provide an equivalent heat transfer capacity. In addition, the cement-sand grouts of the present invention also provide improved bond strengths and decreased permeabilities. The cement-sand grouts can also contain blast furnace slag, fly ash, a thermoplastic air entraining agent, latex, a shrinkage reducing admixture, calcium oxide and combinations thereof.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2001},
month = {Mon Jan 01 00:00:00 EST 2001}
}

Patent:

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  • Preliminary studies were preformed to determine whether thermal conductivity of cementitious grouts used to backfill heat exchanger loops for geothermal heat pumps could be improved, thus improving efficiency. Grouts containing selected additives were compares with conventional bentonite and cement grouts. Significant enhancement of grout alumina grit, steel fibers, and silicon carbide increased the thermal conductivity when compared to unfilled, high solids bentonite grouts and conventional cement grouts. Furthermore, the developed grouts retained high thermal conductivity in the dry state, where as conventional bentonite and cement grouts tend to act as insulators if moisture is lost. The cementitious grouts studied canmore » be mixed and placed using conventional grouting equipment.« less
  • Research commenced in FY 97 to determine the suitability of superplasticized cement-sand grouts for backfilling vertical boreholes used with geothermal heat pump (GHP) systems. The overall objectives were to develop, evaluate and demonstrate cementitious grouts that could reduce the required bore length and improve the performance of GHPs. This report summarizes the accomplishments in FY 98. The developed thermally conductive grout consists of cement, water, a particular grade of silica sand, superplasticizer and a small amount of bentonite. While the primary function of the grout is to facilitate heat transfer between the U-loop and surrounding formation, it is also essentialmore » that the grout act as an effective borehole sealant. Two types of permeability (hydraulic conductivity) tests was conducted to evaluate the sealing performance of the cement-sand grout. Additional properties of the proposed grout that were investigated include bleeding, shrinkage, bond strength, freeze-thaw durability, compressive, flexural and tensile strengths, elastic modulus, Poisson`s ratio and ultrasonic pulse velocity.« less
  • Research commenced in FY 97 to determine the suitability of superplasticized cement-sand grouts for backfilling vertical boreholes used with geothermal heat pump (GHP) systems. The overall objectives were to develop, evaluate and demonstrate cementitious grouts that could reduce the required bore length and improve the performance of GHPs. This report summarizes the accomplishments in FY 98.
  • A building heating and cooling system for using waste heat to thermally energize thermal storage media to control the temperature of a relatively large pool of water is described comprising: conduit means for circulating the water in the pool; a heat pump having a single refrigeration fluid compressor with a suction inlet and a pressure discharge outlet; a refrigerant fluid for use in the compressor; a first fluid-to-fluid heat exchange means in fluid communication with the pressure discharge of the compressor; a first refrigerant fluid reversing valve means in fluid communication with the first fluid-to-fluid heat exchange means; a secondmore » fluid-to-fluid heat exchange means in fluid communication with the first reversing valve means, the second fluid-to-fluid heat exchange means having a first input and output and a second input and output, the second heat exchange means for indirect heat exchange with the water in the pool or spa; a fluid-to-air heat exchange means for indirect heat exchange between the refrigerant fluid in the fluid-to-air heat exchange means and an airspace, the fluid-to-air heat exchange means being fluidly connected to the first output of the second heat exchange means and directly to the first refrigerant fluid reversing valve means without passing through the second reversing valve means; a second refrigerant fluid reversing valve means in fluid communication with the suction inlet of the refrigerant fluid compressor; refrigerant fluid conduit means associated with each of the heat exchange means; valve means operably defining a refrigerant fluid conduit pathway together with the first and second reversing valve means for directing fluid flow direction through the refrigerant fluid conduit pathway wherein the second fluid to fluid heat exchange means operates as a condenser in indirect heat exchange with the conduit means for circulating pool water.« less