Numerical investigation on the heat transfer of particle arrays in supercritical water

The heat transfer characteristics of particles in supercritical water (SCW) are the research foundation for the development of the technology of coal gasification in SCW. The study encounters two challenging problems: the complexity of particle spatial distribution and the special variation of SCW properties. Therefore, this work focuses on contrasting the particle interaction characteristics between in SCW and conventional fluid, instead of the direct study of particle clusters in SCW. Research is conducted by the particle-resolved numerical simulation method. In the simulations, the SCW inflow is 973 K and 25 MPa which is a usual operating condition, and all particle surface temperatures are constant and uniform with the values of 300 K, 672 K and 973 K which are respectively below, at and beyond the pseudocritical temperature zone. The side-by-side and streamwise distributed arrays, which are simple but representative, are adopted as the research objects firstly. The effects of particle number and inter-particle distance on heat transfer are studied. Results indicate that the effects of particle interaction on heat transfer under all heat transfer states are similar in the side-by-side array; while only the effects under the pseudocritical and supercritical states are similar in the streamwise array. Then the structured packed array is adopted, and the effects of void fraction (ε) under different heat transfer states are studied. Moreover, a new correlation dependent on ε and Re is built for predicting the ratio of the Nu of a particle in the structured packed array and that of a single particle.