Abstract
In order to clarify the cooling heat transfer characteristics of CO_2 at a supercritical pressure condition, experimental approach was carried out. The experimental conditions were 9.5MPa for the system pressure and 20 to 70 ℃ for the fluid temperatures. Heat transfer coefficients were measured under the temperature range, and then it was found that the maximum value existed at the fluid temperature of about 45℃. Furthermore, CO_2/Oil mixture was also employed as the experimental fluid. the experiments revealed the heat transfer coefficient decreased by existence of lubricant oil. In order to understand the effect of the lubricant oil on the heat transfer coefficient, flow visualization was achieved through the view section made of acrylic resin tube. It was also clarified that the distribution of the oil changed with varying the fluid temperature, in other words, the flow property of CO_2.
