Centrifugal impeller is usually designed for water pumping. Fluid get energy from impeller but also lose energy when passing through it. To improve the efficiency and have a better operation stability, it is necessary to understand the flow energy dissipation in centrifugal impeller in pump mode. In this case, a thermodynamic analysis is conducted on a model centrifugal pump unit based on computational fluid dynamics (CFD) simulation. Typical performance curve is found with a positive-slope efficiency curve and a negative-slope head curve. With the decreasing of flow rate, both the impeller head and the flow energy dissipation (FED) will rise up. The FED is found related to the flow regime. The complex undesirable flow pattern induces high FED under off-design conditions especially at very small partial-load. Based on the visualization, FED is found with two main sources including the wall friction and the flow interaction. At over-load and design-load, the wall friction induced FED is dominant. With the decreasing of flow rate, flow interaction induced FED becomes dominant. The typical strong FED sites are found related to the striking, separation, merging and interaction of both smooth flow and vortical flow. The FED analysis will correlate the pump performance estimation and guide the design.

离心叶轮通常设计用于抽水。流体从叶轮获得能量，但在通过叶轮时也会失去能量。为了提高效率并获得更好的运行稳定性，有必要了解泵模式下离心叶轮的流动能量耗散。在这种情况下，基于计算流体动力学 (CFD) 模拟对模型离心泵机组进行热力学分析。典型的性能曲线由正斜率效率曲线和负斜率水头曲线组成。随着流速的降低，叶轮扬程和流动能量耗散（FED）都会上升。发现 FED 与流态有关。在非设计条件下，特别是在非常小的部分负载下，复杂的不良流动模式会导致高 FED。基于可视化，FED 有两个主要来源，包括壁面摩擦和流动相互作用。在过载和设计负载下，壁面摩擦引起的 FED 占主导地位。随着流速的降低，流动相互作用引起的 FED 占主导地位。发现典型的强 FED 位点与平滑流和涡流的撞击、分离、合并和相互作用有关。FED 分析将关联泵性能估计并指导设计。