Explicit Multipole Formulas for Calculating Thermal Resistance of Single U-Tube Ground Heat Exchangers
Artikel i vetenskaplig tidskrift, 2018

Borehole thermal resistance is both an important design parameter and a key performance characteristic of a ground heat exchanger. Another quantity that is particularly important for ground heat exchangers is the internal thermal resistance between the heat exchanger pipes. Both these resistances can be calculated to a high degree of accuracy by means of the well-known multipole method. However, the multipole method has a fairly intricate mathematical algorithm and is thus not trivial to implement. Consequently, there is considerable interest in developing explicit formulas for calculating borehole resistances. This paper presents derivation and solutions of newly derived second-order and higher-order multipole formulas for calculating borehole thermal resistance and total internal thermal resistance of single U-tube ground heat exchangers. A new and simple form of the first-order multipole formula is also presented. The accuracy of the presented formulas is established by comparing them to the original multipole method. The superiority of the new higher-order multipole formulas over the existing formulas is also demonstrated.

multipole method

boreholes

calculation

third-order

ground source heat pump (GSHP) systems

second-order

internal thermal resistance

borehole thermal resistance

Författare

Johan Claesson

Lunds universitet

Saqib Javed

Chalmers, Arkitektur och samhällsbyggnadsteknik, Installationsteknik

Energies

1996-1073 (ISSN)

Vol. 11 1 214

Ämneskategorier

Energiteknik

Geoteknik

Husbyggnad

DOI

10.3390/en11010214