CONSIDERATION OF THE REMOVAL OF DESUBLIMATED MATTER IN AN ANNULAR-TUBE COLD TRAP

[摘要] References(3)We have proposed several methods of removing desublimated matter from the cooling surface of a cold trap for the purposes of saving excess heat energy as well as of establishing a continuous process of desublimation. One of the proposals is that an additional action such as thermal stress will make it possible to scrape off the desublimated matter completely by imposing a moderate mechanical force. To confirm the feasibility of this proposal, experimental studies on the scraping-off of the desublimated pure materials water, benzene, p-xylene and cyclohexane have been made by means of an annular-tube cold trap with a Nichrome wire buried in the cooling tube. Several effects of apparent density, sticking surface temperature, use of a thin polytetrafluoroethylene (Teflon) coating layer and thermal stress on the sticking of desublimated matter to the cooling surface have been studied, so that a method for smoothly scraping off the desublimated matter can be found. The experimental results show that the presence of a thin Teflon coating layer and of a Nichrome heater are very useful for easily and completely scraping off the desublimated matter. Also, the stripping behavior is much dependent upon the property of the sticking crystals.