Experimental Performance Evaluation of Miniature Low-Area-Ratio Jet Pumps for High-Temperature Applications

The performance of miniature low-area-ratio jet pumps, critical for achieving high flow amplification, especially in nuclear reactor applications, was experimentally investigated under high-temperature conditions. These jet pumps address constraints of supplying limited inlet flow rates to experimental test devices while ensuring adequate coolant flow rates for nuclear heat removal from the test device. A process system loop was developed to conduct experiments in two stages. In the first stage, the inherent performance characteristics of a single jet pump were evaluated over a wide range of flow ratios, temperatures, and primary flows. Results revealed that significant efficiency improvement takes place by increasing operating fluid (water) temperature from 35°C to 340°C because of reduced fluid viscosity at higher temperatures. In the second stage, a multijet pump assembly, comprising three parallel jet pumps, was characterized to evaluate its performance at temperatures ranging from 30°C to 340°C. The pressure loss across the test device was found to decrease from 7.7 to 5.3 bars because of an increase in fluid temperature enhancing overall system efficiency. Experimental findings demonstrate that the jet pump assembly provides flow amplification from 3.0 to 4.9 as temperature increases from 30°C to 340°C. These results provide valuable insights for optimizing jet pump design and operation in high-temperature applications specifically for nuclear reactors.