Development of vacuum pump driven by thermo-molecular effect of a rarefied gas

在稀薄气体中，即使没有外力作用，气体的温度场在诱导气体的时间无关流动方面也起着重要作用。在这项研究中，我们开发了一种新型的由这些流动驱动的泵（热分子泵）。研究结果如下：1。热边泵：在之前的研究中，热分子泵的驱动力仅限于在具有温度梯度的管道或通道中产生的热蒸腾流。在本研究中，作者设计了一种新型的热边流驱动泵。它是在加热（冷却）物体的锐利边缘附近引起的流动。固体壁的温度梯度在克努森压缩机中是必要的，会导致泵的能量损失，而在新装置中则不需要。对热边泵的性能进行了实验研究。数值模拟的另一个结果是热边泵的设计具有广泛的多样性。微通道热边泵作为一种工作在较高压力（如大气压）下的泵，具有广阔的应用前景。热分子泵的气体分离效果：在热分子泵中，平均自由程的大小是不可忽略的。在这种情况下，气体混合物的速度取决于气体的种类。因此，气体混合物有可能在这些泵中被分离。通过对稀薄混合气体的DSMC模拟，发现热边泵具有相当大的分离效果。

In a rarefied gas, the temperature field of the gas plays an important role in inducing time-independent flows of the gas even if there is no external force. In this study we develop a new type of pump (thermo-molecular pumps) driven by these flows. The results are as follows :1.Thermal Edge Pump :In the preceding studies, the driving force of the thermo-molecular pumps was limited to the thermal transpiration flow, which is induced in a pipe or channel with a temperature gradient. In this study, the author devised a new type of pump driven by the thermal edge flow. It is a flow induced at the vicinity of a sharp edge of heated (cooled) body. The temperature gradient of the solid walls, which is necessary in the Knudsen compressor and causes energy loss of the pump, is not required in the new device. The performance of the new pump -thermal edge pump- was examined experimentally. Another result, which is obtained by numerical simulation, is that the design of thermal edge pumps has wide varieties. The thermal edge pump in the micro channel is promising as the pump which works at higher pressures (e.g.atmospheric pressure).2.Gas Separation Effect of Thermo-molecular Pumps :In the thermo-molecular pumps, the size of the mean free path is not negligible. In this situation, the velocity of the mixture of the gas depends on the spices of gas. Thus it may be possible that the mixture of the gas is separated in these pumps. By using the DSMC simulation of the rarefied mixture of gases, it is found that the thermal edge pump has fairly large separation effect.