Development of the Cooling System for MPU of Mobile Personal Computer

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Mobile personal computers are developing quickly in miniaturization with high performance. With this direction heat generation from the MPU will become higher and higher. And in near future it is supposed to become twice and triple times of the present value. And therefore the high heat generation must be taken into consideration in thermal design of such mobile computers. Recent investigation shows that the heat can be distributed by use of a small size heat pipes. The accumulated heat within the case of the computer, however, must be eventually transferred out of the case by use of some kinds of a fan, which is estimated to be an economic way to solve this problem. In the desk-top mobile computer with a 15〜17 inch display there is fortunately space to set such kind of a ventilating fan.The purpose of the present research is to develop especially small fan with low noise and enough aerodynamic performance. According to a preliminary experiment the noise generated from such a small fan is so low that a conventional sound measuring system is not useful and the input-power is too small to measure. And we proposed to make up a code to measure ultra-low noise level. Now those problems are discussed in a new committee the members of which consisted of the industry, official and learned worlds.We have investigated the noise and fluid-dynamic characteristics and it is clarified that even in the ultra small fans each axial, centrifugal and cross-flow fan has their own peculiar characteristics, however, with quite low efficiency. We cannot have commercial instruments to measure precisely such a small input power. And we could not attain the final object of this project. But we already started to develop new instrument to measure axial torque accurately and we will arrive the final goal very soon.