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Sponsor: National
Rural Electric Cooperative Association
U.S.
Department of Energy
Investigators: J.D.
Spitler, S.J. Rees
Students: W. Austin,
C. Yavuzturk, N. Jain
Description:
Determination of the ground's thermal conductivity is a significant
challenge facing designers of Ground Source Heat Pump (GSHP) systems applied in
commercial buildings. The number of boreholes and the depth and cost of each
borehole are highly dependent on the ground thermal properties. Hence, depending
on the geographic location and the local drilling costs, the ground thermal
properties strongly influence the initial cost to install a GSHP system. In
order to be able to predict ground thermal properties, an experimental
apparatus has been built capable of imposing a heat flux on a test borehole, and
measuring its temperature response. Parameter estimation techniques in
conjunction with a two-dimensional numerical model are used to determine the
thermal conductivity of the surrounding ground.
The initial development of the apparatus and analysis
techniques are described in an M.S.
thesis written by Trey Austin. A more refined version of the analysis
procedures and some validation efforts are described in a paper published in the
ASHRAE Transactions (Austin, et al. 2000) and in Cenk Yavuzturk's
Ph.D.
thesis. Further work aimed at speeding up the analysis
procedure is described in Nagendra Jain's
M.S.
thesis. Ongoing research is aimed at reducing the amount of
time required to make an in situ measurement, reducing the amount of time
required to analyze the results, and further validating the methodology. The
initial work was funded by the National Rural Electric Cooperative Association.
Additional work was funded by the U.S. Department of Energy. Six page summaries
of work done in 1998
and 1999 are
available here.
Publications:
Trey Austin
M.S.
thesis
Cenk Yavuzturk
Ph.D.
thesis
Nagendra Jain's
M.S.
thesis
Gehlin, S. and J.D. Spitler.
2003. Thermal Response Test for BTES Applications - State of the Art 2001.
9th International Conference on Thermal Energy Storage Warsaw, Poland, September
1-4, 2003, pp. 381-387.
Beier, R.A., M. Smith.
2003. "Removing Variable Heat Rate Effects from Borehole Tests".
ASHRAE Transactions. 109(2):463-474.
Beier, R.A., M.
Smith. 2003. "Minimum Duration of In-Situ Tests on Vertical
Boreholes". ASHRAE Transactions. 109(2):475-486.
Witte, H.J.L., G.J. van Gelder,
J.D. Spitler. 2002. In Situ Measurement of Ground Thermal Conductivity:
The Dutch Perspective. ASHRAE Transactions. 108(1):263-272.
Spitler
J.D., C. Yavuzturk and S.J Rees. 2000. In-Situ Measurement of Ground
Thermal Properties. Proc. of TERRASTOCK 2000, Stuttgart, August 2000. Vol. 1,
pp. 165-170.
Austin, W., C. Yavuzturk, J.D.
Spitler. 2000. Development Of An In-Situ System For Measuring Ground Thermal
Properties. ASHRAE Transactions. 106(1):365-379.
Spitler, J.D., S.J. Rees, C.
Yavuzturk. 1999. More Comments on In-situ Borehole Thermal Conductivity Testing.
The Source. Vol. 12, No. 2, March/April 1999. pp. 4-6.
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