X-Ray Radiography and Numerical Simulation of Bubble Behavior in Centrifugal Pump

Boiling heat transfer technology is considered as a promising way to remove the large amount of heat from electronic devices whose heat generation experiences a rapid increase recently. However, by employing the boiling heat transfer, there can be one concern that the pump efficiency may be reduced due to the vapor bubbles flowing into the coolant pump. Therefore, the occurrence mechanism of the pump performance degradation needs to be studied. In this study, a small-size centrifugal pump is selected and the pump performance degradation is investigated by measuring the liquid flow rate by changing the inlet gas bubble flow rate. In addition, the two-phase flow behavior in the pump is visualized and measured by using X-ray imaging. Numerical simulation is also performed to simulate the two-phase flow field around the pump impeller and the simulated results are compared with experiments. As a result, it is observed that the water flow rate decreases abruptly when the air flow rate exceeds a certain threshold value. In addition, both the X-ray imaging result and numerical simulation result shows that the accumulation of air bubbles occurs near the pump inlet, which may affect the water flow rate and in turn the pump efficiency.