In risers, important catalytic processes occur which benefit from the intensive heat and mass transfer in this type of reactor. Typically the reactants are introduced in the liquid phase in the form of small droplets which rapidly evaporate. In this work the effect of this evaporation on the heat and mass transfer is studied using a computational fluid dynamics-discrete element method approach, treating the gas as a continuous phase and the particles and injected liquid as discrete elements. The closures for particle-droplet interaction were obtained from advanced DNS computations reported in literature. The simulations are validated with experiments conducted using air, glass beads and water in a pseudo-2D riser with dimensions 1.57 m x 0.07 m x 0.0065 m. The results indicate that under the experimental conditions (fast fluidization regime and temperatures between 20°C and 150°C), evaporation primarily occurs from the liquid deposited on the particles surface. Significant radial gradients in water vapor concentration prevail, with high concentrations near the wall close to the nozzle. The overall thermal behavior, including asymmetries in the radial profiles, is driven by the strong solids circulation in the bottom section of the riser.

中文翻译：

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冒口系统中液滴注入的传热和传质影响 - CFD-DEM 方法


在冒口中，会发生重要的催化过程，这些过程受益于此类反应器中的强烈传热和传质。通常，反应物以小液滴的形式引入液相中，这些液滴会迅速蒸发。在这项工作中，使用计算流体动力学-离散元方法研究了这种蒸发对传热和传质的影响，将气体视为连续相，将颗粒和注入的液体视为离散元。颗粒-液滴相互作用的闭合是从文献中报道的高级 DNS 计算中获得的。模拟通过在尺寸为 1.57 m x 0.07 m x 0.0065 m 的伪 2D 立管中使用空气、玻璃珠和水进行的实验进行了验证。结果表明，在实验条件 （快速流化状态和 和 $150\mathrm{°}\mathrm{C}$ 之间的温度） $20\mathrm{°}\mathrm{C}$ 下，蒸发主要发生在沉积在颗粒表面的液体。水蒸气浓度呈显著的径向梯度，靠近喷嘴的壁附近浓度较高。整体热行为（包括径向轮廓中的不对称性）是由立管底部强大的固体循环驱动的。