The Experimental study of supercritical CO 2 flow in the porous media for the heat transfer of EGS Reporter :Ming-Che Chung Date : 2014/07/01

Outline Background Purpose Experimental apparatus and procedure Results Conclusions

A novel renewable energy concept is geothermal power. Geothermal energy is the process of extracting the heat generation by earth and harnessing it to drive a power plant. 1 Background

Geothermal systemSystem nameTemperatureDepth Traditional geothermal system Low temperature system <100 ℃ 1,000~2,000m Middle temperature system 100~200 ℃ High temperature system 200~350 ℃ Non-traditional geothermal system Enhanced geothermal system 100~300 ℃ 3,000~5,000m The geothermal system is divided into traditional geothermal system and non- traditional geothermal system.  Geothermal type Table.1. Geothermal system of classification 2

Artificial Fracture Production well Injection well Pump Seismometers What is Enhanced geothermal system (EGS) ? 3 Fig.1. Schematic diagram of EGS

 What’s the Supercritical Fluid 1.A supercritical fluid is any substance at a temperature and pressure above its critical point, where distinct liquid and gas phases do not exist. 2.It can effuse through solids like a gas, and dissolve materials like a liquid. 3.Supercritical fluids are suitable as a substitute for organic solvents in a range of industrial and laboratory processes. 4.Carbon dioxide and water are the most commonly used supercritical fluids, being used for different application. 4

Technique for supercritical carbon dioxide Supercritical CO2 ChemicalEnvironmentalMaterialNanotechnology Biomedical engineering Food Industry Fig.2. Application of supercritical CO 2 5

 Brown propose that supercritical CO 2 is use as working fluid in enhanced geothermal system. 6 Fig.4 CO 2 -EGS Fig.3 Water -EGS

Fluid property Chemical Water: Powerful solvent for rock minerals: lots of potential for dissolution and precipitation. CO 2 : Not an ionic solvent; poor solvent for rock minerals. Fluid circulation in wellbores Water: Small compressibility, moderate expansivity CO 2 : Large compressibility and expansivity. Ease of flow in reservoir Water: Higher viscosity, higher density CO 2 : Lower viscosity, lower density Heat transmission Water: Larger specific heat CO 2 : Smaller specific heat Table.2. Comparison between Water and CO 2  Why use CO 2 as working fluid? 1.Solve the deep geothermal limit of water shortage 2.Special chemical properties 3.Thermosiphon can enhance efficiency 4.Sequestration for CO 2 7

Working Fluid Critical Temperature ( ℃ ) Critical Pressure (MPa)Density(g/cm 3 ) CO H2OH2O CH C2H6C2H C3H8C3H C2H4C2H C3H6C3H CH 3 OH C 2 H 5 OH C3H6OC3H6O Table.3. Fluid temperature and pressure diagram 8

9  For the reason of all of previous studies are limited by the absence of an experimental system to investigate the performance of supercritical CO 2 in the reservoir.  This study determines the performance of heat transfer of supercritical CO 2 with/without porous media in EGS. Purpose

AuthorPurpose Liao 、 Zhao (2002) Yoon et.al (2003) He et.al (2005) Huai et.al (2005) Jiang et.al (2006) Jiang et.al (2008) Jiang et.al (2009) Jing et.al (2009) Li et.al (2010) Niu et.al (2011) Magliocco et.al (2011) Kim et.al (2011) Chen et.al (2013) Jiang et.al (2013)  Paper review Table.4. Reference 10

Yes 11 Pressure set up Test section heated The operating condition achieved CO 2 injected Yes Steady state Data collection Analysis Fig.5. flow chart of experimental Experimental apparatus and procedure

12 Fig.6. Schematic diagram of experimental system Test section Water bath Data logger CO 2 cylinder High pressure pump Heater

Fig.7. Test section P P2 P3 P4 P5 45 cm 90 cm 135 cm 180 cm Tw1 Tw2 13

14 Table.5. Operating conditions Experimental conditions Flow rate 10 mL/min 、 30 mL/min 、 40 mL/min 、 50 mL/min Pressure 7.5 MPa 、 13.7 MPa 、 10.3 MPa Initial wall temperature 150 ℃、 200 ℃ Test section empty tube 、 porous media(1.7 mm) 、 porous media(2.6 mm)

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Results Fig.8. At 13.7 MPa and initial wall temperature 150 ℃ for flow rate in empty tube. (a) Heat transfer coefficient (b) Temperature difference between inlet and outlet (a)(b) 16

Fig.9. At 30 mL/min and initial wall temperature 150 ℃ for pressure in empty tube. (a) Heat transfer coefficient (b) Temperature difference between inlet and outlet (a)(b) 17

18 (a)(b) Fig.10. At 13.7 MPa and 40 mL/min for initial wall temperature in empty tube. (a) Heat transfer coefficient (b) Temperature difference between inlet and outlet

19 Fig.11. At 7.5 MPa and 40 mL/min and initial wall temperature 150 ℃ with/without porous media. (a) Heat transfer coefficient (b) Temperature difference between inlet and outlet (a)(b)

20 Fig.12. Influence of pressure and flow rate on heat transfer in (a) empty tube (b) porous media (1.7 mm) (c) porous media (2.6 mm) (a) (b)(c)

23 Pressure (MPa) Flow rate (mL/min) Heat transfer coefficient (W/m 2 ･ k) Enhance (%) Pressure drop (kPa) Enhance (%) Pressure (MPa) Flow rate (mL/min) Heat transfer coefficient (W/m 2 ･ k) Enhance (%) Pressure drop (kPa) Enhance (%) Pressure (MPa) Flow rate (mL/min) Heat transfer coefficient (W/m 2 ･ k) Enhance (%) Pressure drop (kPa) Enhance (%) Table.6. Compare with effectiveness evaluation between heat transfer coefficient and pressure drop (a) Empty tube (b) Porous media (1.7 mm) (c) Porous media (2.6 mm) 21

 In this study, the heat performance of supercritical CO 2 was investigated in various experimental conditions. The results showed that the use of porous media and a different flow rate increased the heat transfer coefficient, but the flow rate increased to 50 mL/min is not economic, because pressure drop is much larger than 40 mL/min.  Moreover, a static pressure of 10 Mpa enabled excellent performance, because of ºC of pseudocritical temperature at 10 MPa. This study provides data regarding EGS operating conditions. 22 Conclusions

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