Development of the Cooling System for MPU of Mobile Personal Computer

移动的个人计算机正朝着小型化和高性能方向快速发展。在这个方向上，MPU产生的热量将变得越来越高。在不久的将来，它应该是现值的两倍或三倍。因此在这种移动的计算机的热设计中必须考虑高的发热。最近的研究表明，可以通过使用小尺寸的热管来分配热量。然而，计算机机箱内积聚的热量最终必须通过使用某种风扇转移到机箱外，这被认为是解决这个问题的经济方法。在具有15 ~ 17英寸显示器的台式移动的计算机中，幸运的是存在设置这种通风风扇的空间，本研究的目的是开发具有低噪声和足够空气动力学性能的特别小的风扇。根据初步实验，从这样的小风扇产生的噪声是如此之低，以至于传统的声音测量系统是无用的，并且输入功率太小而无法测量。并提出了编制一套超低噪声电平的测量代码。现在这些问题在一个新的委员会中讨论，该委员会的成员包括工业界，官方和学术界。我们已经调查了噪音和流体动力学特性，并且澄清了即使在超小型风扇中，每个轴流式，离心式和横流式风扇都有自己独特的特性，但是效率很低。我们不可能有商业仪器来精确测量如此小的输入功率。我们无法达到这个项目的最终目标。但我们已经开始开发新的仪器来精确测量轴向扭矩，我们将很快达到最终目标。

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.