Predicting the Effective Thermal Conductivity of Some Sand-Water Mixtures Used for Backfilling Materials of Ground Heat Exchanger

지중열교환기 뒤채움재로 사용되는 모래-물 혼합물의 열전도도 예측

  • Sohn, Byong-Hu (Fire and Engineering Services Research Center, KICT)
  • 손병후 (한국건설기술연구원 화재 및 설비연구센터)
  • Published : 2008.09.10

Abstract

This paper presents the results of a laboratory study on the thermal conductivity of and(silica, quartzite, limestone, sandstone, granite and two masonry sands)-water mixtures used for ground heat exchanger backfilling materials. Nearly 260 tests were performed in a thermal conductivity measuring system to characterize the relationships between the thermal conductivity of mixtures and the water content. The experimental results show hat the thermal conductivity of mixtures increases with increasing dry density and with increasing water content. The most widely used empirical prediction models for thermal conductivity of soils were found inappropriate to estimate the thermal conductivity of unsaturated sand-water mixtures. An improved model using an exponential relationship to compute the thermal conductivity of dry sands and empirical relationship to assess the normalized thermal conductivity of unsaturated sand-water mixtures is presented.

References

  1. IGSHPA, 2000, Grouting for Vertical Geothermal Heat Pump Systems : Engineering Design and Field Procedures Manual, International Ground Source Heat Pump Association, Stillwater, Oklahoma
  2. Sohn, B. H., Shin, H. J. and Park, S. K., 2005, Evaluation of effective thermal conductivity and thermal resistance in ground heat exchanger boreholes, Korean Journal of Air-Conditioning and Refrigeration Engineering, Vol. 17, No. 8, pp. 695-703
  3. Lee, S. K., Woo, J. S., Ro, J. D. and Kim, D. K., 2006, A study on the estimation of soil formation thermal conductivities and borehole resistances with one-dimensional numerical model and in-situ field tests, Korean Journal of Air-Conditioning and Refrigeration Engineering, Vol. 18, No. 10, pp. 783-790
  4. Sohn, B. H., 2007, Evaluation of ground effective thermal conductivity and borehole effective thermal resistance from simple linesource method, Korean Journal of Air-Conditioning and Refrigeration Engineering, Vol. 19, No. 7, pp. 512-520
  5. Zhang, Q. and Murphy, W. E., 2000, Measurement of thermal conductivity for three borehole fill materials used for GSHP, ASHRAE Transactions, Vol. 106, pp. 434-441
  6. Kavanaugh, S. P. and Allan, M. A., 1999, Testing of thermally enhanced cement ground heat exchanger grouts, ASHRAE Transactions, Vol. 105, pp. 446-450
  7. Sohn, B. H. and Shin, H. J., 2006, Thermal conductivity measurement of grouting materials for ground heat exchanger borehole, Korean Journal of Air-Conditioning and Refrigeration Engineering, Vol. 18, No. 6, pp. 493-500
  8. Leong, W. H., Tarnawaski, V. R. and Aittomaki, A., 1998, Effect of soil type and moisture content on ground heat pump performance, Int. J. Refrigeration, Vol. 21, No. 8, pp. 595-606 https://doi.org/10.1016/S0140-7007(98)00041-3
  9. Yari, M. and Javani, N., 2007, Performance assessment of a horizontal-coil geothermal heat pump, Int. J. Energy Research, Vol. 31, pp. 288-299 https://doi.org/10.1002/er.1230
  10. Sohn, B. H., 2008, Thermal conductivity measurement of sand-water mixtures used for backfilling materials of vertical boreholes or horizontal trenches, Korean Journal of Air-Conditioning and Refrigeration Engineering, Vol. 20, No. 5, pp. 342-350
  11. Carslaw, H. S. and Jaeger, J. C., 1947, Conduction of Heat in Solids, 2nd ed., Oxford University Press
  12. Rohsenow, W. M., 1973, Handbook of Heat Transfer, McGraw-Hill, New York
  13. KSA, 2002, KS F 2302 : 2002 Test method for particle size distribution of soils, Korean Standards Association
  14. KSA, 2000, KS F 2306 : 2000 Test method for water content of soils, Korean Standards Association
  15. KSA, 2006, KS F 2308 : 2006 Test method for density of soil particles, Korean Standards Association
  16. KSA, 2006, KS F 2324 : 2006 Method of classification of soils for engineering purposes, Korean Standards Association
  17. Kline, S. J., 1985, The purpose of uncertainty analysis, J. Fluids Engineering, Vol. 107, pp. 153-160 https://doi.org/10.1115/1.3242449
  18. Kersten, M. S., 1949, Laboratory research for the determination of the thermal properties of soils, Research Laboratory Investigations, Engineering Experiment Station, Technical Report 23, University of Minnesota, Minneapolis, MN, USA
  19. Johansen, O., 1975, Thermal Conductivity of Soils, Ph. D. thesis, University of Trondheim, Trondheim, Norway. (CRREL Draft English Translation 637, US Army Corps of Engineers, Cold Regions Research and Engineering Laboratory, Hanover, NH, USA)
  20. Farouki, O. T., 1982, Evaluation of methods for calculating soil thermal conductivity, CRREL Report 82-8, US Army Corps of Engineers, Cold Regions Research and Engineering Laboratory, Hanover, NH, USA
  21. Smith, W. O., 1942, The thermal conductivity of dry soils, Soil Science, Vol. 53, pp. 425-459