TY - JOUR
DP - National Agricultural Library
DB - PubAg
JO - Renewable energy
TI - Numerical sensitivity study of thermal response tests
A1 - Wagner, Valentin
A4 - Wagner, Valentin
A4 - Bayer, Peter
A4 - Kübert, Markus
A4 - Blum, Philipp
EP - 2012 v.41
KW - data collection
KW - design for environment
KW - equations
KW - groundwater
KW - heat exchangers
KW - heat pumps
KW - heat transfer
KW - pipes
KW - porous media
KW - renewable energy sources
KW - spatial distribution
KW - thermal conductivity
AN - 1079975
AB - Thermal conductivity and thermal borehole resistance are basic parameters for the technical and sustainable design of closed ground source heat pump (GSHP) systems. One of the most common methods to determine these parameters is the thermal response test (TRT). The response data measured are typically evaluated by the Kelvin line source equation which does not consider all relevant processes of heat transfer in the subsurface. The approach only considers conductive heat transfer from the borehole heat exchanger (BHE) and all transport effects are combined in the parameters of effective thermal conductivity and thermal borehole resistance. In order to examine primary effects in more detail, a sensitivity study based on numerically generated TRT data sets is performed considering the effects of (1) the in-situ position of the U-shaped pipes of borehole heat exchangers (shank spacing), (2) a non-uniform initial thermal distribution (such as a geothermal gradient), and (3) thermal dispersivity. It will be demonstrated that the shank spacing and the non-uniform initial thermal distribution have minor effects (less than 10%) on the effective thermal conductivity and the determined borehole resistance. Constant groundwater velocity with varying thermal dispersivity values, however, has a significant influence on the thermal borehole resistance. These effects are even more pronounced for interpreted effective thermal conductivity which is overestimated by a factor of 1.2–2.9 compared to the real thermal conductivity of the saturated porous media.
PY - 2012
LA -
DA - 2012-05
VL - v. 41
SP - pp. 245-253
DO - 10.1016/j.renene.2011.11.001
ER -