Experimental investigation on heat transfer performance of flowing irregular semi-cokes in heat exchanger with primary recovery method

Abstract

For purpose of improving the waste heat recovery and utilization efficiency of high-temperature semi-cokes, a new heat exchanger with primary recovery method was creatively proposed, and the heat transfer performance of flowing irregular semi-cokes in the new primary heat exchanger was investigated experimentally for the first time. The effects of initial temperature, flow velocity and diameter of semi-cokes on the heat transfer performance of flowing irregular semi-cokes were analyzed, and the experimental correlation formula of Nusselt number between flowing irregular semi-coke and cooling wall was studied by dimensional analysis and experimental data fitting. Furthermore, the heat transfer performance of flowing irregular semi-cokes under the condition of steam flow was compared with those under the condition of no steam flow. Experiment results show that the initial temperature, flow velocity and diameter of semi-coke have significant effects on the heat transfer performance, and the initial temperature and flow velocity have positive effects. The experimental correlation formula of Nusselt number was obtained, and the average relative error of calculation and experiment is 4.46%, which indicates that the experimental correlation formula can well predict heat transfer performance. The heat transfer performance of flowing irregular semi-cokes under the condition of steam flow is better than that under the condition of no steam flow, and the heat transfer mechanism under the condition of steam flow was revealed. Meanwhile, the comprehensive heat transfer coefficient with steam flow is 79.5% higher than that without steam flow. The steam acts as an intermediate heat transfer medium of the flowing irregular semi-cokes and cooling wall, which occupies an important position on the heat transfer enhancement between the flowing irregular semi-cokes and cooling wall.