Experimental investigation of convection heat transfer of CO2 at super-critical pressures in vertical mini-tubes and in porous media

Convection heat transfer of CO2 at super-critical pressures in vertical tubes with diameters of 0.948 and 4 mm and in porous media with particle diameters of 0.2–0.28 mm was investigated experimentally. The local heat transfer coefficients, fluid bulk temperatures, and wall temperatures were measured in the tests which investigated the effects of inlet temperature, mass flow rate, and heat flux on the convection heat transfer in the mini-tube and the porous tube. The variable thermophysical properties of super-critical CO2 and buoyancy significantly influenced the convection heat transfer in the vertical mini-tubes and in the porous media. The convection heat transfer in the porous tubes was very different from that in empty tubes.