Accuracy in residence time measurements

Abstract

NOTATION c' = root-mean-square concentration fluctuation I , = intensity of segregation L, = scale of mixing Nsc = Schmidt number ( v / D ) T = radius r0 = pipe radius t = time G = local mean velocity u' = root-mean-square axial Eulerian velocity fluctuation x = axial distance E = turbulent energy dissipation T = time constant Y = kinematic viscosity LITERATURE CITED

Hydraulic analysis of cell-network treatment wetlands

“…Measured RTDs usually exhibit what is termed upper truncation where late-time, or tail, data are unavailable after some maximum time, t max (Jawitz, 2004). Because RTD complete moments are desired for parameter estimation purposes, measured RTDs are often exponentially extrapolated beyond t max (e.g., Sater and Leverspiel, 1966;Curl and McMillan, 1966;Martinez and Wise, 2003a). Here, RTD complete temporal moments were obtained from the sum of the numerically integrated moments from 0 < t < t max and the moments of the exponential tail (Jawitz, 2004).…”

Errors caused by tracer solubility in the measurement of gas phase axial dispersion

“…However, the finite model (closed boundary conditions) including absorption of tracer gas does explain why kI takes values other than unity. However, as shown by Curl and McMillan (1966), for certain conditions, even a 1% error in material balance could cause as much as 50% error in holdup measurements. They also observed uncertainties of a factor of two when attempting to calculate axial dispersion coefficients by comparing the tracer concentration data with the theoretical curves derived by Brenner (1962).…”

“…It could be argued that a 10% deviation is an acceptable material balance. However, as shown by Curl and McMillan (1966), for certain conditions, even a 1% error in material balance could cause as much as 50% error in holdup measurements. The error in mean residence time determination could lead to even more significant error in determining the variance of residence times.…”

Tracer Methods in Chemical Reactors. Techniques and Applications

“…(7), can lead to large errors in t and even larger errors in the estimation of the variance of the E curve (43). (7), can lead to large errors in t and even larger errors in the estimation of the variance of the E curve (43).…”

“…(15) for the variance (43). The first is rather arbitrary, the second, while theoretically more satisfying, is plagued by the problem that small errors in satisfying eq.…”