Basic flow behavior of supercritical CO_2 in solar water heater using supercritical CO_2 is studied for a flow of supercritical CO_2, a small change in temperature or pressure can result in a large change in density and specific heat capacity, especially in the state close to the critical point. Natural convective flow of the supercritical CO_2 can be easily induced by solar heating in the system,when flow characteristics and heat transfer of supercritical CO_2 natural convection are important.Considering thermophysical properties of CO_2 near the critical point, phase change from liquid to supercritical state have significant effects on the CO_2 local heat transfer behaviors.
