On the estimation of thermal resistance in borehole thermal conductivity test

D. Marcotte and P. Pasquier

Renewable Energy, 2008, vol. 33, issue 11, 2407-2415

Abstract: Sizing of ground-coupled loop heat exchangers (GLHE) depends on the ground thermal conductivity and capacity, and the borehole thermal resistance. One popular method to estimate the thermal parameters is the interpretation of in situ thermal response tests. The modeled response is Tm=(Tin+Tout)/2, the average temperature of the fluid entering and leaving the ground. The Tm response corresponds to the physically unrealistic hypothesis of constant heat flux along a borehole. Using a 3D finite element model of the borehole, we show that Tm does not correspond to the fluid mean temperature within the borehole. Accordingly, with Tm, an overestimation of the borehole thermal resistance results. The resistance overestimation has a noticeable economic impact. We propose instead a new estimator we name “p-linear” average of Tin and Tout with parameter p→-1, as determined by numerical simulations. We show that the p-linear average closely fits the average fluid temperature computed with the numerical model, hence avoiding bias in estimation of borehole thermal resistance. Finally, we discuss the problem of collinearity arising in the estimation of thermal parameters.

Keywords: GLHE standard sizing; Line-source model; 3D numerical borehole model; p-Linear average; Thermal response test; Thermal parameter estimation (search for similar items in EconPapers)
Date: 2008
References: View complete reference list from CitEc
Citations: View citations in EconPapers (79)

Downloads: (external link)
http://www.sciencedirect.com/science/article/pii/S0960148108000372
Full text for ScienceDirect subscribers only

Related works:
This item may be available elsewhere in EconPapers: Search for items with the same title.

Export reference: BibTeX RIS (EndNote, ProCite, RefMan) HTML/Text

Persistent link: https://EconPapers.repec.org/RePEc:eee:renene:v:33:y:2008:i:11:p:2407-2415

DOI: 10.1016/j.renene.2008.01.021

Access Statistics for this article

Renewable Energy is currently edited by Soteris A. Kalogirou and Paul Christodoulides

More articles in Renewable Energy from Elsevier
Bibliographic data for series maintained by Catherine Liu ().