| 摘要 |
<p>PROBLEM TO BE SOLVED: To accurately and efficiently calculate the true mass flow rate of various gas species according to a micro mass flow control technology using ultrasonic nozzles. SOLUTION: Many kinds of gas species are classified into e.g. five groups A-D and typical effluence coefficients Cda-Cde are predetermined for the groups. The upstream pressure and temperature of an ultrasonic nozzle are detected for a gas to calculate a theoretical mass flow rate Qth. In this calculation of the flow rate Qth, a theoretical mass flow rate vs. effluence coefficient table 52 stored in a memory is referred, corresponding to the gas groups A-E, to select a desired effluence coefficient CD (among Cda-Cde). In selection of the coefficient Cd, the true mass flow rate Qtr is obtained according to Qtr= Cd×Qth. Owing to such gas classification, the true mass flow rate Qtr can be measured with a little memory capacity, even if the kind of gas differs or increases.</p> |
