Visualization of Boiling Freon Swirl Flow

This paper presents the visualization of flow boiling in a circular tube under swirl flow by the Real Time Neutron Radiography (RTNR) and the ultra-fast X-ray computed tomography scanner (XCT). The twisted tape inserted in the tube generates the swirl flow. The swirl flow affects the void distribution in boiling flow and heat transfer phenomena. RTNR gives the void distribution in the plane orthogonal to the test section. And, the ultra-fast XCT can measure the instantaneous cross sectional void distribution. The combination of RTNR and ultra-fast XCT can be used to determine in-situ three-dimensional void distribution in complex geometry such as swirl flow boiling. XCT experiments were preformed using Freon 123 as working fluid. RTNR experiments were conducted using Freon 134a at conditions similar to the XCT experiments. The visualization results show that liquid is forced to the heated walls and tape insert in each sub-channel. The understanding of these void distribution characteristics may lead to increased knowledge of the flow boiling mechanisms.