Title

Experimental and analytical investigation on pipe sizes for a coaxial borehole heat exchanger

Document Type

Article

Publication Date

1-1-2018

Publication Title

Renewable Energy

Volume

115

First Page

946

Keywords

Coaxial borehole heat exchanger, Coefficient of performance, Composite coaxial model, Experimental analysis, Fourier number

Last Page

953

Abstract

This paper investigates the use of a vertical coaxial borehole heat exchanger (BHE), focusing on those consisting of standard geothermal piping material, as a component in a ground-source heat pump system. The results of a lab-scale experiment are used to verify the trends exhibited by a recent semi-analytical model, referred to as the composite coaxial (CCx) model, considering short-term behavior when laminar flow is experienced in the annular space of a coaxial heat exchanger. The discussion on pipe sizes is then expanded upon using the suggested model along with a modified design procedure to compare the performances realized by an example heat pump. A comparison is made here between configurations having various nominal inner pipe diameters while maintaining the same outer pipe. The results of the analysis show that increasing the inner pipe diameter, within the verified limit of the composite coaxial model, will reduce the required length of heat exchanger and increase the overall coefficient of performance realized by the heat pump.

DOI

10.1016/j.renene.2017.08.088

ISSN

09601481

E-ISSN

18790682

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