An improved thermal response test for U-tube ground heat exchanger based on optical fiber thermometers

Hikari Fujii, Hiroaki Okubo, Keita Nishi, Ryuichi Itoi, Kunio Ohyama, Kazuo Shibata

Research output: Contribution to journalArticle

134 Citations (Scopus)

Abstract

As part of a new thermal response test (TRT) and to determine ground thermal conductivities, vertical temperature profiles were obtained using retrievable optical fiber sensors inserted into the U-tubes of two ground heat exchangers (GHEs) installed at Maebaru City (Fukuoka, Kyushu) and Kushiro City (Hokkaido), Japan. Measured profiles and outlet temperatures from TRTs were history-matched with the cylindrical source function. Nonlinear regression was used to estimate the vertical distribution of ground thermal conductivities. The computed distribution is consistent with measured data indicating both the reliability of the optical fiber thermometer and TRT interpretation. It is expected that TRTs and optical fiber thermometers will prove to be increasingly useful for optimizing the depth of the GHEs installed in heterogeneous formations, and consequently will minimize installation costs of geothermal heat pump systems.

Original languageEnglish
Pages (from-to)399-406
Number of pages8
JournalGeothermics
Volume38
Issue number4
DOIs
Publication statusPublished - Dec 1 2009

All Science Journal Classification (ASJC) codes

  • Renewable Energy, Sustainability and the Environment
  • Geotechnical Engineering and Engineering Geology
  • Geology

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