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| | Abstract | | Ground thermal use being noticed as a renewable energy is adequately designed with depth and number of heat exchange tubes if heat exchange nature of the ground where the tubes are installed is beforehand measured. Authors made the tool of ground thermal conductivity measurement which is low cost specifications in composition with digital IC thermal sensors and heating cable, with operational manner inside small diameter boreholes, as of construction boring. The tool system for the experiment is 20 meters in length, 1 meter interval of thermal sensors, 25W heating ability of thermal line source and 800W power stabilizer. The experiment was logging through the temperature variation at each thermal sensor along the hole during continuous 25 hour line heating and the successive 20 hours after cut-off heating. The data of temperature variation versus time was transformed to the effective thermal conductivity with 1 meter interval along the hole. Then, the effective thermal conductivity data was used to make simulation of thermal exchange rate, with the specific heat estimated from geologic column and under assumption of initial ground temperature and subsurface fluid temperature. |
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