Explicit multipole formulas and thermal network models for calculating thermal resistances of double U-pipe borehole heat exchangers

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Bibtex

@article{882f032e7864412daa5804de0ff0b726,
title = "Explicit multipole formulas and thermal network models for calculating thermal resistances of double U-pipe borehole heat exchangers",
abstract = "Double U-pipe boreholes are the second most used type of ground heat exchangers after single U-pipe boreholes. The borehole thermal resistance is a key design and performance parameter for the double U-pipe boreholes. Another parameter that is particularly important for double U-pipe boreholes is the internal thermal resistance between the U-pipes. There is, however, a general lack of methods that can be used to calculate the thermal resistances of the double U-pipe boreholes. This article presents explicit multipole formulas for calculating thermal resistances of double U-pipe boreholes with symmetrically positioned pipes. The presented formulas include zeroth- and first-order expressions for the borehole thermal resistance and the internal thermal resistance. The internal thermal resistance formulas cover various possible flow configurations of the heat carrier fluid in the double U-pipes. The accuracy of the presented zeroth- and first-order formulas is established by comparing them to the original 10th-order multipole method. The article also presents thermal network models for computing effective borehole thermal resistance of double U-pipe boreholes from the multipole resistances. Formulas for calculating effective borehole thermal resistance of double U-pipe boreholes are presented for two idealized cases of uniform heat flux and uniform average wall temperature along the borehole.",
author = "Johan Claesson and Saqib Javed",
year = "2019",
doi = "10.1080/23744731.2019.1620565",
language = "English",
volume = "25",
pages = "980--992",
journal = "Science and Technology for the Built Environment",
issn = "2374-4731",
publisher = "Taylor & Francis",
number = "8",

}