Title

A physical and semi-analytical comparison between coaxial BHE designs considering various piping materials

Document Type

Article

Publication Date

12-15-2017

Publication Title

Energy

Volume

141

First Page

1610

Keywords

Borehole heat exchanger, Coefficient of performance, Composite coaxial model, Geothermal heat pump, Thermal response test

Last Page

1621

Abstract

This paper presents an improved semi-analytical model for the heat transfer related to a coaxial borehole heat exchanger (BHE). This model, referred to as the composite coaxial (CCx) model, is verified using results from three different thermal response tests performed on full-scale coaxial BHEs having various pipe size and material properties. The model is further used to analyze the performance and length requirements of various coaxial configurations comparing the use of a steel outer pipe to an insulated inner pipe. This comparison is made considering standard HDPE pipe sizes as the status quo, where the parameters are kept within the verified tested limit of the model. The results show, in comparison to using an insulated inner pipe, that a steel outer pipe has a greater impact on reducing the overall length requirement while maintaining system performance.

DOI

10.1016/j.energy.2017.11.001

ISSN

03605442

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