Investigation of particle flow characteristics in internal and external combined heat exchanger

To address the challenge of inefficient waste heat recovery from high-temperature solid particles, crucial for energy-intensive industries, an internal and external combined heat exchanger was proposed. This novel design enhances energy efficiency in industries like metallurgy and carbon production, potentially saving significant amounts of standard coal annually. The flow characteristics of particles were studied with a visual experimental platform and equidistant point method. The flow patterns near the top and on both sides of the internal heat exchanger present “W” and “U” shaped symmetrical distribution, respectively. The particle size has a significant impact on flow trajectory and average velocity, but the initial velocity has a negligible effect. The variation range of flow trajectory with a particle size of 11 mm is 5 times that of 1.8 mm. As the particle size increases from 1.8 mm to 11 mm, the average velocity in X-axis direction of the particles increases from 6.1 × 10⁻⁶ m/s to 1.2 × 10⁻⁵ m/s. For particle sizes from 1.8 mm to 11 mm, the Y-axis velocity fluctuates within 4.7 × 10⁻⁵ to 6.4 × 10⁻⁵ m/s, and for initial velocities from 3 × 10⁻⁵ to 7 × 10⁻⁵ m/s, the Y-axis velocity deviates by less than 4.3 %. This work uniquely reveals how particle parameter governs flow dynamics in complex heat exchanger geometries, providing critical insights for optimizing waste heat recovery.