The sound development of knowledge for generalized saturated and subcooled pool boiling critical heat flux (CHF) mechanisms and corresponding correlations for various test heater configurations and surface conditions in water and other wetting liquids are becoming increasingly important as the fundamental database not only for the design such as the high heat flux cooling systems using subcooled water pool boiling, but for the super-conducting magnets cooled by liquid helium and liquid nitrogen, the thermal control of microelectronic assemblies cooled FC liquids for future super-computers. Firstly, the subcooled pool boiling CHF data measured using test horizontal cylinders were investigated to clarify the effect of test cylinder diameters in water and ethanol on the CHF. The CHF data for larger diameter cylinders were clearly divided into two groups for low and high subcooling. The CHF correlations representing the CHF resulting from the hydrodynamic instability (HI), and the heterogeneous spontaneous nucleation (HSN), were derived for the wide ranges of subcooling and pressure including the effect of test cylinder diameter respectively. Secondly, it was observed experimentally that there existed the CHF resulting from HI measured for the same size horizontal cylinders with commercial, rough and mirror surfaces (CS, RS and MS) in a pool of water which agreed with one another independently of the surface conditions at lower pressures for lower subcooling. Thirdly, nonlinear trend of subcooled water flow boiling CHF versus outlet subcooling for flow velocities at outlet pressures in horizontal or vertical tubes with twisted tapes of twist ratios having flowing subcooled water was studied using existing database based on the corresponding correlations extending the new correlations with different mechanisms recently developed for the nonlinear trend of CHF in through tubes with wide ranges of inside diameter, and length-to-diameter ratio for wide ranges of flow velocities, outlet pressure and outlet subcooling.
Main engine inspection and maintenance are important tasks carried out by the engine crew. Nevertheless, a case example where carelessness such as the failure to properly lubricate the connecting rod bolt led to insufficient bolt clamping which eventually resulted in engine damage has been reported. Since it is important that uniform standard procedures for bolt tightening be equally adopted in all ships, the authors sent out questionnaires regarding bolt tightening practices and procedures to marine engineers who work for Japanese shipping lines. The results obtained from the responses of 85 engineers showed that there are multiple views regarding bolt tightening managements, such as the type of lubricant used, the method of lubricant application, and the method of tightening for bolts in the same engine part.
On March 11, 2011 the biggest earthquake in the history of Japan occurred off the east coast and the subsequent tsunami devastated the coast and many ports of Japan. Many ships including small leisure boats, fishing boats, coasting vessels and even large ocean going vessels in the ports suffered major damages due to the tsunami attack. Almost all ports damaged by the tsunami remained closed for a long time due to many submerged debris in the approach channels. The authors investigated and analyzed the type and number of ships, and the degree of damage inflicted on the ships as well as on the port facilities to estimate the causes of these damages. Finally earthquake and tsunami countermeasures for ships including the evacuation from ports to prevent damage to ships moored in the ports were considered.
The authors used the isolate, Vibrio sp., as a model strain to estimate the survivability of pathogenic V. cholerae after invasion from ballast water discharged into Tokyo Bay. The seawater samples taken from Tokyo Bay were also examined for V. cholerae contamination. All samples tested negative for V. cholerae. As for the survivability of Vibrio sp., the initial number of the cells, in the order of 103 to 104 colony-forming units (CFU) ml-1, was drastically reduced in vitro within 2 weeks of incubation under competition with 103.5 to 106.1 CFU ml-1 of the indigenous population. On the other hand, Vibrio sp. cells could grow in the seawater previously autoclaved. The indigenous population was not affected at all even in the presence of Vibrio sp. cells. These results indicate that V. cholerae cells have less potential to survive after invasion. The utilization of H2O2, with a final concentration of 0.3% in seawater, was shown to be effective for the pasteurization of seawater taken from busy ports in the vicinity of southeastern Japan.
In conjunction with the developments in the computer technologies over the last three decades, lifting surface methods based on the circulation theory are often used for the design and analysis of screw propellers. In this study, the flow around of propeller blades is analyzed and performance characteristics of screw propellers have been examined for the different cases such as various pitch ratios, blade numbers and expanded ratios. To do this analysis, KUMS’s (Kobe University Maritime Sciences) programbased on lifting surface theory, which was generated in the Kobe University, has been used. The KUMS’s code models the flow around of the propeller by representing the blade and wake as a discrete set of vortices and sources, which are properly distributed on the mean camber and wake surfaces to represent blade loading and blade thickness respectively. Finally, a series of results have been obtained in the case of standard screw propellers and results are compared with those of experimental data whose geometric characteristics were given in the literature and PUF code written by Kerwin. Subsequently, general assessments have been done about attained results.
A surface of carbon steel was modified with a rubbing technique to improve the corrosion and wear resistant properties in seawater. With this technique, Si fine particles were embedded into and adhered onto the surface of carbon steel, and then Zn was coated on the modified surface using the friction stir process. The formed surface of carbon steel showed good corrosion and wear resistant properties in seawater.
Emission regulations for ships have become increasingly strict. In 2016, Tier 3 regulations will be implemented by the International Maritime Organization (IMO) which makes the reduction of NOx emissions in Emission Control Areas (ECA) by 80% obligatory. Thus, there is a pressing need to develop emission control technologies in order to meet these stringent regulations. Generally, in exhaust emissions treatment, there are trade-off problems to be solved. The aim of this research is to simultaneously reduce CO2, NOx, PM, and SOx. The authors developed a system in which an emissions charger and electrostatic water scrubber using corona discharge are used with Ca(OH)2 solution. PM can be collected using static electricity by spraying electrostatic water. O3 emanating from the corona discharge can convert NO into NO2, and NO2 and SOx can dissolve well in water. In addition, Ca(OH)2 can detoxify waste water generated by aftertreatment. Using this emission reduction technique, NOx, SOx and CO, and PM were reduced by 75 %, 80 %, and 100%, respectively.