Hiroyuki Toyoda

A Design for Loop Thermosyphon Including Effect of Non-Condensable Gas

We have developed a loop thermosyphon for cooling electronics devices. Its cooling performance changes with the ambient temperature and amount of input heating. Especially it deteriorates with non-condensable gas (NCG) increase. NCG leakage of thermosyphon cannot detect below under 10−10 Pa-m3 /s, though we have to design the thermosyphon considering these characteristics to provide guaranteed performance for 5–10 years. In this study, the effect of the amount of NCG in each component of a thermosyphon was measured while changing the amount of heater input, and the amount of NCG. As a result, we obtained some useful design information. The performance of air cooling part does not depend on the NCG amount in this case. The performance of evaporation part depends on the total pressure that includes the partial pressure of vapor and the partial pressure of NCG. The performance of condensation part is deteriorated strongly by NCG amount increase. Additionally, we expressed these performances as approximations. These expressions let us predict the total thermal resistance of this thermosyphon by the NCG amount and the input heating amount. Then, using the leakage of a thermosyphon and the amount of dissolved NCG in water, we predicted the amount of NCG that will be in the thermosyphon after 10 years. These results also let us predict the thermosyphon’s total thermal resistance after 10 years. Though there is a slight leakage on thermosyphon, using this technique, we are able to design a thermosyphon that is guaranteed the cooling performance for a long term.Copyright

Cooling Design for the Next Generation Optical Disc Drive

Recently, the data transfer rate and the memory capacity of optical disc drives have been increasing dramatically. To obtain the high data transfer rate and greater memory capacity, the disc rotation speed and the laser power also need to be increased and these cause an increase in the temperature of the laser diode. Therefore, to develop the next generation optical disc drives, an enhanced cooling system is indispensable for the optical pick-up unit that contains the laser diode. As the temperature of the pick-up unit is influenced by the inside air flow induced by the disc rotation, it is quite necessary to grasp the velocity and temperature distribution inside the drive, and also the influence of the disc rotation speed on the temperature of the pick-up unit. Hence we applied PIV measurements and CFD simulations to visualize the flow field and the internal temperature. Then, during the actual disc recording process we measured the temperature of the pick-up unit and the internal air of the drive. As a result, we made clear the dependence of the disc rotation speed on the pick-up unit temperature. In addition, as an example for next generation optical disc drives, we evaluated the cooling system applying a small axial fan inside the drive and confirmed the validity of this fan system.Copyright ?? 2007 by ASME

Cooling Technology for the Optical Disc Drive using Air-flow induced by Disc Rotation

Recently, data transfer rates of optical disc drives have been dramatically increasing. To obtain the high data transfer rates, disc rotation speed and laser power also need to be increased. Therefore, to develop the next generation optical disc drives effectively, enhanced cooling system of the optical pick-up unit which includes the laser diode is indispensable. The cooling performance of the pick-up unit is directly influenced by the inside airflow induced by the disc rotation. Tb maximize the effect of the airflow around the pick-up unit, we applied the combination of PIV (Particle Image Velocimetry) and CFD (Computational Fluid Dynamics) simulation. It was made clear that the tray opening near the pick-up unit increased the cooling performance effectively.

DESIGN OF A SMALL-SIZE INTERLOCKING SYSTEM WITH HIGH AVAILABILITY

This paper presents a rail traffic controlling system that emphasizes safety and reliability. The system uses an inter-locking design that has a logical unit and a power controlling unit. A circuit within the system also provides high availability.