Before a rotameter can be used to measure an unknown flow

Chapter 3, Problem 3.13

(choose chapter or problem)

Before a rotameter can be used to measure an unknown flow rate, a calibration curve of flow rate versus rotameter reading must be prepared. A calibration technique for liquids is illustrated below. A flow rate is set by adjusting the pump speed; the rotameter reading is recorded, and the effluent from the rotameter is collected in a graduated cylinder for a timed interval. The procedure is carried out twice for each of several pump settings. ROTAMETER VARIABLE SPEED PUMP Rotameter Collection Volume Reading Time (min) Collected (cm3 ) 2 1 297 2 1 301 4 1 454 G 4 1 448 6 0.5 300 6 0.5 298 STOPWATCH 8 0.5 371 8 0.5 377 GRADUATED 10 0.5 440 CYLINDER 10 0.5 453 (a) Assuming the liquid is water at 25C, draw a calibration curve of mass flow rate, m(kg/min), versus rotameter reading, R, and use it to estimate the mass flow rate of a water stream for which the rotameter reading is 5.3. (b) The mean difference between duplicates, D;, provides an estimate of the standard deviation of a single measurement, which was given the symbol Sx on p. 18 of Chapter 2: fi- - Sx = 2 D; = 0.8862D; Moreover, confidence limits on measured values can be estimated to a good approximation using the mean difference between duplicates. For example, if a single measurement of Y yields a value Ymeasured, then there is a 95% probability that the true value of Y falls within the 95% confidence limits (Ymeasured - 1.74D;) and (Ym