Wiped film evaporators (WFEs) are characterized by small hold-up and short residence times, making them well suited for the separation of thermally sensitive substances and for fast chemical reactions. Since fluid dynamics and heat transfer in WFEs are highly interdependent, the effects of different wiper geometries, operating parameters and physical properties on the residence time behavior are manifold and poorly understood. In this work, the influence of liquid load, wiper speed and liquid viscosity on the residence time distribution (RTD) of a wiped liquid film was investigated. Tracer experiments were conducted without evaporation in a stainless steel WFE alternatively equipped with a spring-loaded comb wiper and a roller wiper. A detailed comparison of both wipers demonstrated that at a high liquid load and an increased viscosity, shorter residence times were achieved with the roller wiper, which could be explained by a strongly pronounced bow wave with an increased vertical flow velocity. Using a comb wiper, an increase in dispersion with rising liquid load at higher viscosity was demonstrated.

刮膜式蒸发器（WFE）的特点是滞留量小，停留时间短，非常适合热敏性物质的分离和快速的化学反应。由于WFE中的流体动力学和传热高度相关，因此对刮水器几何形状，工作参数和物理特性对停留时间行为的影响是多方面的，人们对此知之甚少。在这项工作中，研究了液体负载，刮水器速度和液体粘度对刮擦液膜的停留时间分布（RTD）的影响。示踪剂实验在不带蒸发的不锈钢WFE中进行，该WFE还配备了弹簧式梳状刮水器和辊式刮水器。对这两种擦拭布的详细比较表明，在高液体负荷和高粘度的情况下，辊式刮水器的停留时间更短，这可以用垂直流速增加的强烈的弓形波来解释。使用梳子擦拭器，在较高粘度下，随着液体负荷的增加，分散性得到了提高。