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

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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.