JP Journal of Heat and Mass Transfer
Volume 9, Issue 2, Pages 135 - 154
(May 2014)
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RESEARCH INTO THERMAL CONDUCTIVITY OF GROUT MIXTURES USED FOR HEAT PUMP BOREHOLES
Petr Bujok, Martin Klempa, Michal Porzer, Robert Rado and Pavel Pospisil
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Abstract: The article summarises some basic knowledge obtained by research into the properties of mixtures used in the grouting of boreholes used for heat pump installation. Already for a long time, our Institute has been concerned with research into the thermal permeability of various types of grout mixtures – from the commonly used cement-clay mixtures, which have good grouting properties but rather bad thermal transmittance, to the mixtures (available on the market) that are pre-prepared and are to be only mixed with water at a given ratio. On the one hand, they have better thermal properties, but on the other hand, they are more expensive and if some of them are injected into boreholes they will harden in several days so that the function of protection in relation to the heat exchanger will disappear. Our Institute co-operates with the Institute of Geonics of AS CR and AGH Kraków in making comparative measurements of thermal conductivity and thermal permeability of these various types of grout mixtures, and on the basis of obtained results, in proposing possible methods of the grouting of heat pump boreholes. For the determination of thermal conductivity and volumetric heat capacity a device ISOMET 2104 from the company Applied Precision is used at the Institute of Geonics AS CR and for the determination of thermal permeability an apparatus of Institute’s own design, called TermoSTEND, is utilised. |
Keywords and phrases: geothermal energy, heat pumps, grout mixture, thermal conductivity. |
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