Experimental Study of Heat Transfer Coefficient and Pressure Drop for Supercritical Carbon Dioxide and Water Inside a Microchannel

Abstract

The thermo-fluidic nature of water and supercritical carbon dioxide in a microchannel is experimentally studied. A test rig and microfluidic devices are constructed to enable precise control and measurements of temperature, pressure, heat and mass fluxes.. Wall temperature measurements, heat transfer coefficients, and pressure drops for both fluids were directly measured and compared.. Flow regimes and characteristic Rynolds numbers were discussed and were related to Dittos-Boelter and Gnielinski correlations. It was found that an exponential fit better predicted the wall temperature profile obtained for supercritical CO2. Moreover, for conditions close to the pseudo-critical point, the correlations failed to predict the supercritical heat transfer coefficient but fit well in the gas-like supercritical CO2 conditions. It was also found that water has a better ability to remove heat under the conditions studied in this paper with smaller pressure drop. However, for water the pressure drop was a significant portion of the operational pressure.