Heat transfer characteristic of particle flow around the out-wall of different geometries

In this study, large-scale simulations were carried out for different tube banks to explore the effect of geometrical factors. In addition, the heat transfer experiment of dense particles was carried out to validate the heat transfer model used in discrete element method. The stagnation zone and void zone with nearly triangular shape are found in staggered tubes. The stagnation zone with rectangular shape is formed between vertical adjacent tubes of the aligned tube, and the width of stagnation zone is one third of the tube diameter. A triangular particle blockade zone is formed in the rectangular stagnation zone. The heat transfer rate of staggered tubes is increased by 26% compared with that of the aligned tubes. The staggered elliptical-like combined tubes bank with chamfers significantly increase the heat transfer rate by 54.2% with the same heat transfer coefficient, compared with the staggered circular tubes bank. The local heat transfer performance can be enhanced by the addition of chamfers at the junction area of tubes. When penetration thermal resistance is dominant compared with the contact thermal resistance, the circular tube has higher heat transfer coefficient compared with elliptical-like combined tube with chamfers. The thermal resistance models for different tubes are developed.