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Flashing Experiment of liquid nitrogen in a pressure vessel was conducted under rapid depressurization rate. Observations of the explosive boiling behavior caused by quick opening of a electro-magnetic valve were undertaken by using a video camera. Pressure and temperature changes in the vessel were measured. Depressurization rates in these experiments fell in the range from 0.01 to 4.0MPa/s. Experimental results showed that the initial temperature distributions and depressurization rates have more intrinsic influence on these flashing phenomena. Relationship between pressure undershoot and depressurization rate was obtained. The rate of pressure recovery was found to increase with the rate of depressurization, which also resulted in the increase of the increment of pressure recovery. The empirical equation proposed by Alamgir and Lienhard was applied to predict the recovery pressure of the flashing of liquid nitrogen. To obtain more precise prediction of the pressure recovery, another factor such as an orifice diameter that affects the discharge condition of the recovery pressure. [ABSTRACT FROM AUTHOR]

Latent heat of vaporization of water is very large compared to the latent heat of vaporization of other fluids. Therefore, when evaporation is promoted by decompressing, water lowers the temperature and freezes finally. We froze without heat exchange by exposure to vacuum the water using a vacuum pump. Despite violent boiling occurs, pressure in the vessel was going down. But, finally, at freeze process, the pressure in the vessel was increased. This pressure rise is caused by that amount of evaporation increases temporarily rapidly. The rapid increase in the amount of evaporation is due to the release of latent heat during freezing. This paper was focused on the pressure temperature change and mass change when the phase change of the water is switched to sublimation from the evaporation. This is likely to provide useful information when considering a phase-change model in a special state. [ABSTRACT FROM AUTHOR]

Okinawa National College of Technology has developed a food processing machine using underwater shock waves. Several prototype machines were developed, and experimental results (sterilization, improvement of juice extraction, milling flour, emulsification etc.) were obtained. After deciding food materials to be processed and the desired processing results, we designed and manufactured a pressure vessel for experiments. In this report, the process flow for designing and manufacturing a pressure vessel for softening meat using underwater shock and its concept design are described. The relationships among the number of shock waves, the distance between the shock wave generation point and the meat, the backing material, and the amount of softening ware experimentally compared. We measured the velocity of the shock wave penetrating to the inside of the meat, from which we estimated the particle velocity. We developed computer simulation model using the estimated particle velocity in the meat. Using the results of the analysis obtained from the computer simulation model, we designed and fabricated the pressure vessel. [ABSTRACT FROM AUTHOR]

We perform herein a direct observation of shockwave propagation using a high-speed camera and estimate properties, such as acoustic velocity and Hugoniot parameter, using the impedance matching scheme to reveal the dynamic characteristics of Okinawa's unique soil "Shimajiri Mahji." A computational simulation corresponding to the experimental setup is then conducted. A comparison of the numerical and experimental results demonstrates their fairly good agreement, which suggests that the experimentally estimated dynamic characteristics of "Shimajiri Mahji" are valid. In addition, a computational simulation based on the smoothed particle hydrodynamics is also modeled and performed to elucidate the fragment behavior when the unexploded bomb explosive is at the soil surface. From a series of computational results, we have confirmed and clarified that the fragment behavior is significantly dependent on the amount of explosive charge and soil characteristics. [ABSTRACT FROM AUTHOR]

To clarify the shock characteristics of Okinawa's unique soils "Jahgaru" that is widely distributed in southern part of Okinawa Main Island, an experimental investigation of dynamics properties such as shockwave propagation, pressure and particle velocity have been performed using impedance matching method. Therefore, we have also obtained the Hugoniot date of "Jahgaru". And then, to reveal a validity of the material characteristics, a computational model for the experimental procedure using ALE simulation have been developed. A comparison between numerical results and experimental ones, the capability of proposed method through the numerical simulations have been confirmed. [ABSTRACT FROM AUTHOR]

We have been investigating underwater-explosion-induced shockwave-propagation phenomena for use in a robust food-processing system. This system comprises a high-voltage capacitor bank with a gap switch, water tank, and wire explosive. We performed an optical examination of the shockwave generated by a wire explosion using an electrical discharge in the water tank. Simultaneously, we measured the shock pressure and investigated the effects of various electrical characteristics upon the shockwave propagation phenomena. To obtain various strengths of the underwater shockwave, 0.6-, 1.0-, and 1.4-mm width wires made from 1.0-mm-thick aluminum plates were used at various voltages. As an example, a shockwave with a propagation velocity of 1,600 m/s was observed from an explosion generated using a 1.0-mm-width aluminum wire. We found that the strength of the shockwave could be controlled by the applied discharge voltage and wire size. [ABSTRACT FROM AUTHOR]