The rapid gas dynamic expansion in a free jet is used as a tool to investigate the creation of the condensed phase out of the gas phase by nucleation and cluster growth. Starting from experimental results that yield information about the existence of clusters and the heat transferred to the gas phase, the modeling of a gas-cluster system is presented using a molecular kinetic approach which considers the mass and energy transfer between gas and clusters in the free-molecular flow regime. Some numerical results are presented which show fair agreement with the experimental results. However, it is stressed that considerably more detailed information, which could possibly obtained now from numerical experiments, is needed to be able to further refine models for the fluxes at phase interfaces, especially for small systems.
The flow patterns of the air-water two-phase flow in horizontal-upward inclined pipes were studied experimentally in order to obtain basic information on the flow characteristics of gas-liquid two-phase flows in hilly-terrain pipelines. Flow regime maps in horizontal-upward inclined pipes were expressed by the combination of a basic flow pattern and some auxiliary flow patterns. In addition to the effect of inclination angle on the flow pattern, their mutual relation between one in horizontal and others in inclined part was described. Comparisons of the flow regime maps with those obtained in single horizontal or upward inclined pipes without bending part were carried out.
As a basis of designing unlined caverns for storage of liquid petroleum gas, terminal rising velocities VT and drag coefficient CD of single bubbles in a stagnant liquid filling in narrow parallel walls were measured in the present study using air and water at atmospheric pressure and room temperature. The gap width dδ of the parallel walls was varied from 300μm to 900μm. The bubble diameter de was from 1mm to 20mm. It was confirmed that VT was affected by δ as well as de. In addition, rising motion of a bubble was found to be classified into two states: one is the state of low VT when de is small and the other is that of high VT when de is large. Transition between these states was observed when de was intermediate size. Empirical correlations of VT and CD for each state were developed by taking into acount forces acting on a bubble.
The effects of liquid viscosity on the rising velocity of a large gas bubble in a stagnant liquid, and on the flow parameters of slug flow were experimentally investigated using a 19.2mm diameter vertical tube with air and liquid as working fluids. The liquids used in the present experiment were water and glycerol solutions, and the kinematic viscosity of these liquids ranged from 0.83×10-6 to 15.5×10-6m2/s. The important parameters in slug flow such as the rising velocity of large gas bubbles, liquid slug length, liquid film thickness around large gas bubbles etc., were measured. As a result, it is clarified that the rising velocity of a large gas bubble in a stagnant liquid decreases only slightly with increasing liquid viscosity. On the other hand the rising velocity in flowing liquid, i.e., in slug flow increases with increasing liquid viscosity. These results are discussed in relation to the liquid film thickness around large gas bubbles. Furthermore, the mean values of gas and liquid slug lengths and the ratio of their standard deviations to mean values of their length are examined by paying attention on the effect of liquid viscosity.
The correlation of droplet deposition rate is one of the most important constitutive equations in predicting the thermohydrodynamic behavior of annular dispersed flow based on the three fluid model. In view of this, quantitative comparison and evaluation of typical correlations of droplet deposition coefficient were made. The result indicated that the correlations show different dependencies on gas flux and droplet concentration and the considerable scattering in predicting the droplet deposition coefficient particularly for the higher gas fluxes and lower pressures.
Development of a new fluid-drive gas compressor using magnetic fluid and traveling magnetism is in progress as a joint work of Kumamoto University and Mitsui Miike Machinery Co., Ltd. The principle and the feature of the compressor, and the progress to date are briefly described in this report.