Flow energy transformation and dissipation mechanisms of carbon dioxide, nitrogen, and water jets

Abstract

Supercritical carbon dioxide (SC–CO2) shows many advantages in the exploitation of shale gas and geothermal energy. This condition is mainly because pressure synergizes with temperature in rock-breaking. A computational model was established on the basis of an experimental setup and validated with experimental data to study the energy transformation and dissipation mechanism. The jet fields of water, SC-CO2 and nitrogen were studied. Result shows that the jet center pressure and temperature difference are in the following descending order: SC-CO2 > nitrogen > water, indicating that SC-CO2 jet can produce the maximum broken volume. The SC-CO2 and nitrogen temperature drops are induced by endothermic expansion, and the water temperature increment is caused by viscous heating. The total pressure underestimates the energy of SC-CO2 and nitrogen flows, which is harmful to safety risk control. The dissipation rate of flow energy is in the following ascending order: SC-CO2 < nitrogen < water. This condition is because less large eddy energy transfer is produced in SC-CO2 and nitrogen jets than water jet, and shock wave leads to more energy loss of nitrogen than SC-CO2. The temperature drop in jets shows that SC-CO2 and nitrogen have the potential for enhanced heat transfer. The findings provide a deeper understanding of efficient control and the use of SC-CO2 flow energy.