An experiment was conducted to study the heat transfer characteristics of supercritical pure R41

mixtures of CO2/R41 (20.5/79.5)

and CO2/R41 (51.4/48.6) cooled in a horizontal smooth mini-channel tube with inner-diameter of 2 mm. Mass flow rate was in the range of 400 to 800 kg·m-2·s-1

pressure changed from 6.0 to 8.0 MPa

heat flux ranged from 12 to 48 kW·m-2 and bulk temperature varied from 20℃ to 80℃. The maximum heat transfer coefficient (α) of the three fluids increased with the CO2 mass fraction. Additionally

α of pure R41 is smaller than that of the mixtures. However

α variation tendency of the mixtures is the same as that of pure R41. α of the three working fluids are ranging from 2 kW·m-2·K-1 to 25 kW·m-2·K-1 under the present test condition. The influence of pressure is significant. The closer of the pressure approaches the critical pressure

the higher of the maximum α is. The heat flux has little influence on α when the bulk temperature is far away from the critical temperature. However for the bulk temperature near the critical temperature

α increases with the decrease of heat flux. The experimental results are compared with prediction values calculated by twelve correlations. It is concluded that four correlations predicting with good precisions

and the errors are within ±30%. Nevertheless

the prediction errors increase with CO2 mass fraction.