Performance analysis of medium-depth coaxial heat exchanger geothermal system using CO2 as a circulating fluid for building heating.

Autor: Shi, Yan, Bai, Ze, Feng, Guanhong, Tian, Hailong, Bai, Hao
Zdroj: Arabian Journal of Geosciences; Jul2021, Vol. 14 Issue 14, p1-17, 17p
Abstrakt: The medium-depth geothermal energy embodied in the rocks 2~3 km underground is an optimal heat source with appropriate temperature for building heating. Using water as a circulating fluid causes corrosion of wellbore materials and an increase in the pump power to overcome flow resistance and increases the circulating fluid velocity. The objective of this paper is to investigate the heat transfer mechanism and optimization strategy of using CO2 as a circulating fluid in a medium-depth coaxial heat exchanger geothermal system (MDCHEs). We use the T2Well simulator to build a wellbore-reservoir coupled model and verify it using existing experimental research. The heat extraction performance of CO2-based and water-based MDCHEs is compared by a numerical model. The effects of the pressure difference between the injection and production, mass flow rate, and specific enthalpy change on heat production performance are discussed. In addition, the heating performance and potential environmental benefits of CO2-based MDCHEs are also analyzed. The results show that CO2-based MDCHEs increases the heat extraction rate by 31% compared with the water-based MDCHEs. Moreover, CO2-based MDCHEs can reduce 116124.86 tons of pollutant emissions per year. The modeling and analysis methods presented here may provide a theoretical reference for the selection of a working fluid and the improvement of heat extraction performance in geothermal engineering developments. [ABSTRACT FROM AUTHOR]
Databáze: Complementary Index
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