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Evaluation of Effective Thermal Conductivity and Thermal Resistance in Ground Heat Exchanger Boreholes  

Sohn Byong Hu (Fire & Engineering Services Research Department, KICT)
Shin Hyun-Joon (Fire & Engineering Services Research Department, KICT)
Park Seong-Koo (Fire & Engineering Services Research Department, KICT)
Publication Information
Korean Journal of Air-Conditioning and Refrigeration Engineering / v.17, no.8, 2005 , pp. 695-703 More about this Journal
Abstract
The objective of this study is to determine the effective thermal conductivity and thermal resistance values in test boreholes with three different fill materials. To evaluate these heat transfer properties, in-situ tests on four vertical boreholes were conducted by adding a monitored amount of heat to water over various test lengths. Two parameter estimation models, line-source and numerical one-dimensional models, for evaluation of thermal response test data were compared when applied on the same four data sets. Results show that the average thermal conductivity deviation between measured data and these two models is in the range of $3.03\%$ to $4.45\%$. The effect of increasing grout thermal conductivity from 1.34 to 1.82 $W/m^{\circ}C$ resulted in overall increases in effective formation thermal conductivity by $11.1\%$ to $51.9\%$ and reductions in borehole thermal resistance by $11.6\%$ to $26.1\%$.
Keywords
Effective thermal conductivity; Effective borehole thermal resistance; In-situ thermal response test; Parameter estimation model; Formation;
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