Method for monitoring liquid nitrogen flow rate utilizing temperature variation
A temperature change, liquid nitrogen technology, applied in the direction of measuring flow/mass flow, measuring device, liquid/fluid solid measurement, etc., can solve harmful, manpower-consuming, suffocation and other problems
Inactive Publication Date: 2005-09-14
INST OF SEMICONDUCTORS - CHINESE ACAD OF SCI
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Problems solved by technology
Using this method requires users to check the flow rate of liquid nitrogen from time to time, which becomes the most labor-intensive part in the normal operation of MBE. The bigger disadvantage is that it directly discharges the nitrogen gas from liquid nitrogen gasification in the room, which is harmful to working in this environment. very harmful to the staff
Working in this hypoxic environment for a long time will cause chest tightness, headaches, and if the nitrogen concentration is too high, suffocation may even be life-threatening
[0004] At present, there is another commonly used method is to discharge the nitrogen outlet to the outside, which solves the problem of hypoxia in the working environment, but this method is not very accurate in judging the flow rate of liquid nitrogen, and this method still cannot put people at risk. Free yourself from this boring monitoring job
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[0019] see figure 1 Shown, the present invention utilizes temperature change to monitor the method for liquid nitrogen flow rate equipment connection mode as figure 1 Shown:
[0020] In order to prevent the vaporized gas and liquid nitrogen of liquid nitrogen from being discharged indoors, a liquid nitrogen output pipe is connected to the output end 5 of the liquid nitrogen consumption device 3, and the outlet of this pipe is connected to the outdoor 4, so that the liquefied nitrogen can be discharged Outdoors, prevent excessive nitrogen levels in the indoor air.
[0021] Although directly connecting the nitrogen output port to the outside has fundamentally solved the old problem of liquid nitrogen gasification gas being discharged indoors, how to monitor the flow rate of liquid nitrogen has become a problem. Because the user generally cannot see whether the outdoor exhaust port 4 is in a gas state or a gas-liquid mixed state, and the outdoor outlet of nitrogen is too far aw...
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The invention relates to a method for using temperature changes to monitor flow rate of liquid nitrogen, which comprises following steps: a) placing a temperature sensor in the outlet of liquid nitrogen equipment, which is connected to an instrument connected to computer interface RS232; b) using computer to constantly monitor temperature change state of temperature sensor; c) adding a bend in the outlet adjacent to liquid nitrogen equipment and placing temperature sensor in bend bottom; d) placing a temperature sensor in liquid nitrogen equipment outlet and using a computer to monitor temperature to directly ascertain flow speed of liquid nitrogen, then determining if liquid nitrogen is needed to adjust; when temperature exceeding fixed number, users will being warned.
Description
technical field [0001] The method of the present invention is suitable for the occasion where liquid nitrogen is used for refrigeration and the flow rate of liquid nitrogen is required to be monitored, especially in molecular beam epitaxy (MBE, Molecular Beam Epitaxy) equipment. Background technique [0002] In the process of using liquid nitrogen for cooling, such as the application of molecular beam epitaxy (MBE), it is required to adjust the flow rate of liquid nitrogen. Because the flow rate is too small, the cavity wall may be cooled unevenly, so that the impurity molecules in the vacuum chamber escape from the screen wall, and the vacuum degree in the vacuum chamber decreases, which affects the growth quality of the material; if the flow rate is too high, it will cause liquid The waste of nitrogen, so how to control the flow rate of liquid nitrogen is a very important issue. [0003] In order to solve this problem, the most commonly used method at present is to connec...
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IPC IPC(8): G01F1/688
Inventor 孙永伟
Owner INST OF SEMICONDUCTORS - CHINESE ACAD OF SCI