Well-established recommendations exist for the sizing of safety valves and the connected inlet and outlet lines for steady-state, single-phase gas/vapor or liquid flow. However, in the case of a two-phase vapor/liquid flow, the required relieving area to protect a system from overpressure is larger than that required for single-phase flow. This report includes a widely usable engineering tool for the sizing of the typical safety valves. It is based on the omega parameter method, which is extended by a thermodynamic non-equilibrium parameter. The recommended sizing procedure starts with the definition of the sizing case and includes a method for the prediction of the mass flow rate required to be discharged and the dischargeable mass flux through a safety valve.
In order to mitigate severe accidents of nuclear power plants, a passive safety system is one of influential measures. As the passive safety system uses natural power such as gravity and/or phase changes instead of electrical power, multiphase flows appear in the system. In this paper, multiphase flows in the passive safety system are introduced from several developments. First, a PCCS uses condensation in heat transfer tubes to remove decay heat. Second, oscillated water-vapor multiphase flow can provide cooling water to the heated surface of core-catcher cooling channel. At last, three-phase flows comprising gases, solid aerosols and liquids in safety measures against severe accidents are mentioned.
In high speed turbopumps for rocket engines, the cavitation occurs and often causes the flow instabilities such as the cavitation surge and the rotating cavitation. The flow instability due to the cavitation is called “cavitation instability” and has been a severe problem in the development of liquid fuel rockets. The mechanism of the occurrence of the cavitation instability in turbopump inducers, the suppression method of the instability, and the current state of the numerical simulation of cavitating flow in turbopumps are discussed.
This study aims to evaluate evacuation safety by using several crowd dynamics models based on self-driven particles. In this paper, we implemented two models, namely, the social force model and the RVO model. The social force model is a dynamics model that solves a motion equation. The RVO model is an expanded model of velocity obstacles for collision avoidance among moving objects. When we try to understand the characteristics of those models, the results are as follows. If the desired speed of particles is over 3.5 m/s, the flow coefficient of the social force model declines because of increasing the frequency of clogging. On the other hand, the flow coefficient of the RVO model does not decline. As regards an application to evacuation from a building, the flow of a room declines because of the crowded corridor.
To control safe administration of injection product, we should carefully handle foreign matters. Hospital sometimes encountered cases where insoluble matter formed during the preparation of injections. In order to deal with this situation, we discussed the mechanism of formation of the insoluble matter and countermeasures on manufacturing process. Insoluble matter was a critical problem for quality of drug product of injections. In this report, the review for general approach for the foreign matters on injection product was reported.
In the cleaning process of semiconductor device manufacturing, it is necessary to control the velocity, frequency, and size of droplets of the two-fluid jet method to avoid the feature damage. In this study we attempted the control of droplets generation using capillary tube and surrounding airflow. The generation process is visualized by high-speed photography. As a result, the droplets generation frequency can be controlled in the wide range, by utilizing the resistance of the capillary tube. The droplet diameter monotonically decreases with the airflow rate increased. In addition, it is found that the transition from droplets to liquid column formation at the nozzle tip greatly affects the generated droplets size. Using different liquids, which have different viscosities and surface tensions, and capillary tubes of different contact angles, the transition condition is investigated. The results indicate that the inertia and surface tension of liquid have a dominant role and contact angles of capillary has a small influence.