Release of liquid CO2 from the bottom of a duct

Abstract

This paper presents experimental results of the rapid phase transition of liquid CO2 released from the bottom of a small rectangular duct (BR). The aim is to consider the factors influencing the phase transitions and the release rate if the rupture area is below the liquid level. The tests are initiated by rupturing the diaphragm separating the test section from an atmospheric chamber. Pressure and temperature measurements are used to analyze the phase transition. Also, a high-speed shadowgraph technique is used to visualize the waves. The results are compared with previous top-release tests (TR), where the rupture area is sited above the liquid level. Test results show that the duct’s outlet flow behavior for the BR differs from the TR tests, wherein the gas/two-phase flow is choking. In the BR tests, the shadowgraph images demonstrate that when the liquid/two-phase flows out, the liquid/vapor interface remains nearly fixed until it breaks up. This behavior indicates that the headspace vapor has little influence on the initial evaporation in the BR tests. The results from the current BR tests indicate a lower degree of superheating than in the TR tests (it decreases by 34% for LVF = 66.0%), and the evaporation rate is 1.2–1.8 times faster.