Thermal investigations of supercritical CO2 jet impingement and its cooling applicability in a machining context

In recent years, the use of supercritical carbon dioxide (sCO2) as cutting fluid during machining operations has gained attention of the manufacturing community. The present paper intends to address thermal characteristics of sCO2 free jet impingement on a hot plate. An experimental approach has been hereby chosen in order to assess the heat transfer coefficient (HTC) in various experimental conditions. Infrared thermography along with high speed imaging are set up in order to access the cooling of a titanium plate. HTC is then calculated from an analytical solution of the heat transfer equation adapted to the specific conditions of the proposed setup. Investigations are focused on the influence of nozzle-to-plate distance (from 4 to 106 times jet diameter), angle of incidence (from 90 degrees to 50 degrees) and flow initial temperature ( 40 degrees C to 80 degrees C ) and pressure ( 100 bar to 285 bar). Results provide with metric and dimensionless values of the HTC. Preliminary conclusions are drawn from the presence of solid carbon dioxide at the plate's surface and leads are proposed to investigate in further detail the effect of the jet nature and structure on its cooling ability.