Finite Element Analysis Of Cryogenic Liquid Temperature And Flow Rate On The Underground Temperature Field

摘要

During in-situ heating of oil shale, it is often necessary to seal the underground retort with a frozen wall of ice to isolate the targeted interval from groundwater and to prevent pyrolysis products from escaping. In this study, we have developed a numerical model of the underground freezing and heat transfer processes for a single row of frozen pipes to assess the impact of oil shale heating on the underground freeze wall. Temperature fields under different cooling conditions were analyzed using ANSYS analysis software and the influence of cryogenic coolant temperature and flow rate on underground the temperature field was determined. The simulation results show that lower coolant temperatures and the higher flow rates result in shorter freezing times, as expected, but also that there are optimal combinations of these parameters to minimize freezing time. Elapsed time for freezing and capital and operating costs can be effectively reduced using these results. Using an air-cooled refrigeration unit and limiting coolant temperature to between -15 and -5°C, the optimum coolant flow rate is 40 -50 m~3/h; when using a refrigeration unit and coolant temperatures between -25 and -20°C, the optimal freezing liquid flow rate is 35 to 40 m~3/h.