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Characterization of Choked Conditions Under Subsonic to Supersonic Flow in Single‐Phase (Supercritical to Gaseous CO 2 or Liquid H 2 O) and Multiphase (CO 2 and H 2 O) Transport
Author(s) -
Park Jong Gil,
Han Weon Shik,
Han Gidon,
Piao Jize,
Park Eungyu,
Kwon Sanghoon
Publication year - 2019
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1029/2018jb016824
Subject(s) - supercritical fluid , choked flow , thermodynamics , supersonic speed , speed of sound , shock wave , flow (mathematics) , supercritical flow , materials science , shock (circulatory) , compressible flow , chemistry , multiphase flow , compressibility , analytical chemistry (journal) , mechanics , physics , chromatography , medicine
In geologic media, fluids exist in gas, liquid, and supercritical phases, generating multiphase and multicomponent systems. As fluids migrating through geologic fractures reach the speed of sound, choked flow can be developed in microfractures. To elucidate such choked flow, thermodynamic analysis and numerical simulations were conducted with CO 2 , H 2 O, and CO 2 ‐H 2 O mixtures at various phases ranging from supercritical to gaseous CO 2 and liquid H 2 O. Compressible CO 2 , with a relatively low speed of sound (~225 m/s at 31.1 °C and 7.38 MPa), demonstrated significant changes in thermodynamic properties with small pressure and temperature variations. In contrast, H 2 O, having a relatively high speed of sound (1,524 m/s), showed little thermodynamic variation. For CO 2 ‐H 2 O mixtures, a small addition of CO 2 (or H 2 O) dramatically reduced the speed of sound relative to those for pure H 2 O or CO 2 . For an idealized converging‐diverging microfracture with CO 2 flow, choked flow and a shock wave were generated as outlet pressure was decreased to less than 6.8 MPa. The H 2 O flow did not generate choked flow at any outlet pressures. For CO 2 ‐H 2 O mixtures, choked flow was generated when the CO 2 void fraction was greater than 0.7 with an outlet pressure of 6.5 MPa, indicating that presence of H 2 O inhibited occurrence of choked flow. Choked flow and shock waves can occur in various geologic environments including geologic CO 2 sequestration, geothermal energy development, geysers, and volcano eruptions.