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Heat Pipe Science and Technology, An International Journal

ISSN Print: 2151-7975
ISSN Online: 2151-7991

Archives: Volume 1, 2010 to Volume 8, 2017

Heat Pipe Science and Technology, An International Journal

DOI: 10.1615/HeatPipeScieTech.v2.i1-4.60
pages 43-53

PERFORMANCE OF GEOTHERMAL THERMOSYPHON USING PROPANE

Thomas Grab
TU Bergakademie Freiberg, Gustav-Zeuner-Strasse 7, 09599 Freiberg, Germany
Thomas Storch
Institute of Thermal Engineering, TU Bergakademie Freiberg, Gustav-Zeuner-Strasse 7, 09599 Freiberg, Germany
Ulrich Gross
Institute of Thermal Engineering, TU Bergakademie Freiberg, Gustav-Zeuner-Str. 7, 09599 Freiberg, Germany
Steffen Wagner
Institute of Drilling Technology and Fluid Mining, Technische Universitat Bergakademie Freiberg, 09596 Freiberg, Germany

ABSTRACT

Approximately 46% of the household heat pumps installed in 2011 in Germany are combined with geothermal heat exchangers [3]. Geothermal heat can be extracted by standard heat exchangers such as U-tubes or coaxial tubes, through which a fluid is circulated. A more effective way to extract geothermal heat is through using the thermosyphon principle where a fluid with a low boiling temperature (e.g., propane) is circulated through the heat exchanger. A combination of both types of heat exchangers can be very effective for heating and cooling as the heat is stored in the ground and helps the underground temperature to regenerate much faster. At the energy park of the TU Bergakademie Freiberg in Germany, a heat pump system based on geothermal thermosyphons combined with geothermal brine tubes is currently under evaluation. The present work is focused on the operating performance of this heating and cooling system. The experimental plant is equipped with various measuring devices including a fiber-optical sensor attached on the outside of the tubes. The present paper reports the effect of various operating parameters on the temperature profiles along the tubes combined with pressure and temperature measurements at the heat pump system, and finally its power consumption. The amount of extracted and introduced energy per day will be presented, leading to conclusions for an effective operating regime. The operation of geothermal thermosyphons proved to be effective; there is however some need for further optimization, for example the evaluation of measured data shows that film spreading cannot be expected along the whole inner tube surface.