Pressure drop data for distillation sieve trays have been obtained with experimental trays with small outlet weir heights, including zero, and for trays with small perforations which exhibit large pressure drops due to surface tension. These data have been added to literature data to form a large composite data base with extensive variations in fluid and gas properties, flow rates, and tray designs.A new pressure drop correlation has been developed which retains the use of the dry tray pressure drop, but provides new procedures for estimating liquid inventory and the resistance to vapor flow due to surface tension forces. This correlation gives a mean absolute error of 6.0% and an average error of -0.6%. These errors are significantly less than the errors between measurements and preldictions from two other correlations using the same composite data base. D. L. BENNETT SCOPEPressure drops across distillation column sieve trays should be estimated accurately as part of column designs to determine downcomer backup, column pressure drop, and tray efficiency. These pressure drop calculations become more important in designs for nonfouling service, where small tray spacings are used and flooding limits tray capacity.The objectives of this paper are: a. To determine whether the liquid inventory on a sieve tray can be measured by a tray-mounted manometer, or whether the inventory should be estimated from the total measured pressure drop by subtracting the other pressure drop components.b. To report sieve tray pressure drop data from trays with low outlet weir heights, including zero, and for trays with small perforations which exhibit large surface tension pressure drops.c. To develop a composite data base, consisting of the above data and literature data, which has large variations in fluid and gas properties, flow rates and tray designs.d. To develop a simple pressure drop correlation for sieve trays based on this composite data base, and to compare the accuracy of this correlation with that of several other correlations, using the same data base. CONCLUSIONS AND SIGNIFICANCETray-mounted manometers had been suggested as possible tools for direct measurement of clear liquid head on aerated sieve trays. Time-average measurements made on special trays with fixed liquid inventories showed large discrepancies with known average liquid heads, dependent upon vapor flow rates and clear liquid heads. Therefore, clear liquid heads were determined from total pressure drop measurements from an independent evaluation of surface tension resistance and conventional dry hole pressure drops.Pressure drop data are reported in Table 1 for trays with small weir heights and small perforation sizes. These data were added to literature data to develop a large composite data base with the extensive range of fluid and gas properties, flow rates, and tray designs summarized in Table 2. A pressure drop correlation has been developed using this composite data base. The total pressure drop is assumed to consist of the dry tray component, the liq...

Kner is an effective Knudsen number, defined byThe flux density on the wall is given by and a is the probability that a particle-particle collision does not significant for very small particles possessing sufficient thermal energy to escape the attractive London-van der Walls force where S t p k is defined as C, ( A l l ) result in agglomeration. The probability a may be quite zap UkPp Stpk = 9P (Dahneke, 1976)' Here we sufficiently large for a to be nil. that the particles are Manuscript receioedjune 28,1979; reoisionOver 1 000 sets of data for forccd convective hailing of distilled water, ethylene glycol and aqueous mixtures of ethylene glycol are reported. Most of these data were taken in the annular flow regime. These data indicate a previously unrecognized Prandtl number effect on the hoiling heat transfer for hoth pure components and mixtures. A significant reduction in thc heat transfer coefficient is observed for mixtures attrihutablc to mass transfer effects. An expression is developed which accounts for hoth of these effects and correlates the experimental data to within a mean deviation of 14.9%. This correlation reduces to the standard Chen correlation for pure fluids with Prandtl numbers close to unity.

A phenomenologically based model for froth height was developed using the assumption of both vapor-and liquid-continuous

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A n understanding of the eddy diffusivity on a distillation tray is important to