Numerical Investigation on the Heat Transfer Characteristics of Supercritical Water in a Non-Uniformly Heated Tube for a Supercritical CFB Boiler

In this paper,a numerical model was built by ANSYS FLUENT to investigate the heat transfer performances of supercritical water in a circumferential non-uniformly heated vertical tube.The Shear Stress Transport(SST)k-ωmodel was adopted for describing turbulence.The operating parameters are chosen according to a 660 MW ultra-supercritical CFB boiler.The heat transfer performances under different operating parameters,such as boiler load,flow direction and heat flux distribution are analyzed.The temperature and heat flux on inner wall varies along the circumference and show symmetric distributions.The overall heat transfer performances at each cross section are better than the local heat transfer performance of midpoint of heating side.Flow direction has a great influence on heat transfer performance;it changes the radial distribution of axial velocity and then affects the turbulence distribution.Therefore,upward flow condition shows a better heat transfer performance.Smaller heat flux improves both the overall and local heat transfer performances.Reducing the heat flux area is not conducive to the overall heat transfer,but does not affect the local heat transfer at the midpoint of heating side.Finally,a new correlation is fitted based on the simulated results of supercritical water heat transfer with circumferential non-uniform heat flux distributions.