Development of the Cooling System for MPU of Mobile Personal Computer

移动个人电脑正朝着小型化、高性能的方向快速发展。在这个方向上，MPU产生的热量会越来越高。在不久的将来，它应该会变成现值的两到三倍。因此，在这种移动计算机的热设计中必须考虑高产热率。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，计算机机箱内积累的热量最终必须通过某种类型的风扇转移到机箱外，这被认为是解决这个问题的一种经济方法。在15~17英寸显示屏的台式移动计算机中，幸运的是有空间设置这样的通风风扇。本研究的目的是开发出噪声低、空气动力性能好的特别小的风扇。根据初步实验，如此小的风扇产生的噪声如此之低，以至于传统的声音测量系统无法使用，并且输入功率太小而无法测量。并提出了建立超低噪声水平测量编码的设想。现在，由工业界、官员和学术界组成的一个新的委员会正在讨论这些问题。我们调查了噪声和流体动力学特性，澄清了即使在超小型风机中，每台轴流风机、离心风机和横流风机也有自己的特点，但效率很低。我们不能用商业仪器来精确测量如此小的输入功率。我们无法实现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，我们很快就会达到最终目标。

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.