Thermal-hydraulics performance evaluation of bubble swarms sweeping tube bundles in a direct contact gas-liquid-solid reactor

Abstract

Direct contact gas-liquid-solid reactor pertains to an extremely high efficiency heat-exchange facility in industrial application. Nevertheless, the scarcity of quantitative analysis data hinders the optimal design of this type of reactor. In the present study, a novel variable bubbles size modeling approach which considers the bubble swarms breakup and coalescence rates, is proposed to evaluate the complex thermal-hydraulics performance of bubble swarms sweeping tube bundles. On the basis of verifying the responsibility of the numerical modelling with published experimental data, the intrinsic link of hydrodynamics and thermodynamics parameters on reactor features, including field characteristics, gas holdup, bubble swarms diameter distribution, gas–liquid interfacial area, temperature difference and heat flux inside different tube bundles regions, are deeply revealed. Results demonstrate that the temperature difference between bubble swarms and tube bundles walls is approximately equal to 2 K. Interestingly, different positions of heat exchanging tubes affect the peak value of circumferential heat transfer coefficient. For typical Tube 1–2, the maximum value of 3146.28 W/m2·K appears around 162°. The presence of tube bundles gives rise to the well-distributed iso-surfaces of bubble swarms which contributes to enhance heat transfer. When superficial gas velocities are respectively 0.09 m/s, 0.12 m/s and 0.14 m/s, the average bubble warms diameters are 13.47 mm, 16.22 mm and 17.24 mm. When initial liquid phase height increases from 342 mm to 378 mm, the corresponding gas–liquid interfacial area decreases by 16.2 % in total. Finally, two new modified dimensionless correlations were developed for the prediction of gas holdup and Nusselt number. The prediction errors are respectively 10 % and 6 %. The findings can improve the awareness for promising applications in design and scale-up processes of direct contact gas-liquid-solid reactor.