Experimental investigation on heat transfer and pressure drop of kerosene at supercritical pressure in square and circular tube with artificial roughness

An experiment on supercritical kerosene heat transfer and flow characteristics in square and circular flow channels with ribbed roughness was carried out at Xi’an Jiaotong University. The wall temperature distribution and pressure drops in the tubes were obtained in the experiment. The coking characteristic of the square tube was also analyzed, with the method of wall temperature variation with the time. Experimental conditions included pressures of 5–22MPa, velocities of 15–60m/s, and maximum heat flux of 40,000kW/m2. Four different ribbed structure square tubes and two ribbed circular tubes were tested. Compared with the smooth tube, the experimental results showed the ribbed roughness can improve the heat transfer performance while the pressure drop in the tubes is increased. It was found that of either the square tube or the circular tube, the tube with the ratio of rib pitch to height 7.5 can get the best integrated heat transfer and pressure drop effect. With the increase of velocity, the coking is significantly improved, and the initial coking temperatures for the square smooth and ribbed tube are about 370°C and 410°C, respectively. The introduction of ribbed roughness also has the benefit of the coking weakening. The heat flux when coking occured in the ribbed roughness square tube was much higher than that of the smooth square tube. For assessing the engineering application, and for deeper understanding of the rib effect on the heat transfer and pressure drop, more ribbed structures need to be investigated.