Thermodynamic Effect and Cavitation Performance of a Cavitating Centrifugal Pump

The thermodynamic effect which affects the cavitation performance of a cavitating centrifugal pump was investigated experimentally using liquid nitrogen. To measure the pump cavitation performance, a test setup which could carry out experiments using both liquid nitrogen and cold water was constructed. The test setup consisted of a suction tank, a test pump, a mass flow meter, a ball valve and pipes. Vacuum-insulated pipes were used. The test pump was a centrifugal type magnetic pump, and two impellers, which differed in cavitation performance, were used in experiments. Cavitation performance using liquid nitrogen or cold water could be obtained from the measurement of the pump suction and delivery pressure, the pump suction and delivery temperature, and the discharge flow rate. And an improvement in pump cavitation performance could be seen when comparing the experimental results from using liquid nitrogen with those from using cold water. The experimental results indicated that cavitation performance using liquid nitrogen was better than that using cold water. This improvement in cavitation performance was thought to be due to the thermodynamic effect of cavitation. And the estimated temperature depression due to the thermodynamic effect decreased with a decreasing flow coefficient. Moreover, it was shown that the estimated temperature depression due to the thermodynamic effect on the low cavitation performance impeller was larger than that on the high cavitation performance impeller at the same flow coefficient.