Takayuki Fujimoto

Development of Cooling Structures for Blu-Ray Disc Compatible Optical Disc Drives Using Computational Fluid Dynamics Based on Cartesian Grid Method

High-performance, simple cooling structures for optical disc drives compatible with the Blu-ray disc (BD) were developed using unsteady numerical flow simulation based on the Cartesian grid method. In the new structure, an additional hole in the tray outside of the disc induced a secondary upward flow, which is caused by a pressure difference and rotating-disc flow. The secondary flow decreases the ambient air-temperature of the laser diode below the hole, and furthermore it increases the velocity around the laser diode and enhances the heat transfer rate. The experimental results indicate that the cooling effect of the laser diode increases, and the disc vibration is not influenced by the additional hole in the tray. The cooling structures are applied to the so-called super-multi BD drive, which achieved 4X high-speed recording for the first time in the industry.Copyright

Estimation Method of Temperature Distribution and Energy Saving Technology of Air Conditioner in Data Center

Reducing the energy consumption of a data center has recently become important because the data center market is rapidly expanding. We developed the “IT-facility linkage system” to deal with this energy saving requirement. This system reduces the amount of energy consumed in a data center by linking two systems, one is the optimized server load allocation system and the other is the air conditioning optimization control system. One of the key technologies of the “IT-facility linkage system” is the precise prediction of the server inlet temperature. If we can comprehend the future temperature distributions, we can reduce the amount of energy consumed in a data center by consolidating the IT load to the more effectively cooled servers. We carried out computational thermal fluid dynamics to predict server inlet temperatures and evaluated the prediction precision by comparing the measured temperature data for this paper. As a result, we found out that when we use a detailed rack model and reproduce the characteristic air flow of a data center such as the recirculation, we can precisely predict the server inlet temperature to within less than one degree.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.