Test methods for components used in vertical geothermal heat exchangers (NT TR 572)

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  • Report #: NT TR 572
  • Approved: March 2005
  • Author(s): Mattias Stenlund
  • Hits: 1

Abstract

This report treats the development of test methods for performance test of components used in vertical geothermal heat exchangers (GHX). The aim of the method proposals, attached to this report, is to help evaluate their performance in laboratory conditions, whilst subjected to relatively realistic environment. Such test methods are missing presently. This is of great concern since the number of GHX’s rapidly increases presently which might endanger the quality of ground water and the reliability of the heat exchanger itself, unless performance of the components used are adequately evaluated. The methods also enable national requirements regarding performance of GHX-components to be set up.

The project focused on the most commonly used components in the Nordic countries and on those that was regarded most important to keep the environmental impact to a minimum as well as to keep the functionality and reliability of the GHX to a maximum. Thus, the resulting method proposals are:

  1. Leakage performance of well tops when subjected to hydrostatic pressure load and their ability to withstand mechanical lift force due to build up of ice on the collector wall.
  2. Leakage performance of cast case sealing when subjected to hydrostatic pressure load. A concrete block kept in a thermally controlled environment simulates the borehole.
  3. Leakage performance of non-cast case sealing and plug sealing when subjected to hydrostatic pressure load. A concrete block or steel pipes kept in a thermally controlled environment simulates the borehole.
  4. Ability of collectors, i.e. plastics pipes, to resist external hydrostatic load in constant temperature.
  5. The method proposals were developed from theoretical and practical investigations, in close contact with experts and key persons in the area.

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