Error analysis of thermal response tests

Comparison of two different models for pile thermal response test interpretation

“…Surprisingly R b , which is generally considered to be determined with less accuracy from thermal response tests [14,22], shows only a small percentage variation, generally within ±15% for the line source case. For the G-function analysis, the results are very stable with variation of less than 1% after the first few hours The preceding sections present a number of analyses, more than could be conducted on a routine basis.…”

“…The test was first proposed for use with borehole heat exchangers in 1983 by Mogensen [10] and then further developed in the 1990's [11,12]. Its application for boreholes is therefore well understood [13,14]. However, the model that underpins normal test interpretation methods assumes that a steady state is rapidly reached within the heat exchanger, allowing the test to be completed within two or three days.…”

“…These equate to around 4% and 10% of the expected values. Larger intervals were used for the thermal resistance as it was expected to be able to determine this parameter to a lower level of accuracy [14,22]. Table 3 summarises the thermal conductivity and thermal resistance values determined from the thermal response test data using the line source model and the G-functions with a constant applied power ( Table 1).…”

“…It tests a larger volume of soil than laboratory methods and gives a lumped value of thermal conductivity of the soils that will be activated by the heat exchanger. Overall accuracies are quoted at 5 to 10% for thermal conductivity and 10 to 15% for thermal resistance [13,14,22,23]. …”

Evaluation of the Internal and Borehole Resistances during Thermal Response Tests and Impact on Ground Heat Exchanger Design

“…This results in 27 different combinations from which the internal resistance was calculated using the multipole method ( Figure 13). It is known that parameter estimation during a thermal response test is very sensitive to the accuracy of assumed parameters [20,21]. Some of which are geometric, like the borehole radius and the shank spacing, while others can be associated to the physical properties, like the thermal conductivity of the grout.…”