Heat transfer analysis of submerged combustion vaporizer under subcritical pressure and comparison with supercritical pressure

The boiling heat transfer under subcritical pressure is used in the vaporization process of submerged combustion vaporizer (SCV). In this paper, the SCV heat transfer calculation model is established by using the method of enthalpy segmentation. Based on this model, the temperature field, heat transfer characteristics and influencing factors of SCV under subcritical pressure are analyzed. The results show that the heat transfer inside tube under subcritical pressure is mainly single-phase convective heat transfer, the boiling heat transfer takes up a small proportion of tube length, but the enhancement degree is higher. In terms of the influence of operating load, 0.3 times standard load is the load threshold value of the SCV in calculation, on both sides of the threshold value, the flow boiling heat transfer coefficient shows an opposite correlation with the operating load. Due to the dominant role of nuclear boiling, the average heat transfer coefficient under subcritical pressure is higher than that under supercritical pressure, but the corresponding fuel gas consumption increase as well. Therefore, the SCV units operating under subcritical conditions can get better heat transfer performance by increasing the pressure to near critical level.