Prospectus

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DST-21 Tray Efficiency Loss with Low Entrainment

Traditional Research Idea

Expected Benefit to Members: Improved tray efficiencies and predictions via an improved understanding regarding the occasions where efficiencies drop steeply – with increasing rates – due to reasons other than entrainment. Present Situation and Proposed Research: It has become clear that entrainment may not be the cause of efficiency loss at high loads, for some of the common FRI tray designs. Some sieve tray designs lose efficiency for reasons not related to entrainment – such as jetting, spraying, eddy diffusivity, decreasing TG’s, etc. Additional experimental work is probably required. Before a detailed test plan can be devised, the FRI databank and the literature need to be reviewed. The Tray Blowing program (DST-1) would certainly impact this study. Also, the on-going OSU valve tray efficiency modeling project will probably impact this study, because a key component of that project is the impact of jetting on tray efficiency. It is possible that the OSU project will explain, in large part, tray efficiency losses, at high rates, in the absence of entrainment. Proposed Internals and Test System: New trays will probably need to be fabricated. Tray spacings will probably be 36 inches. Entrainment will need to be measured – accurately. Jetting will probably need to be created – and measured. Estimated Unit Time: Four man-weeks for databank review and literature study. At least four weeks of LP Column Operation. Estimated Additional Costs (Beyond Unit Time): None Background and Discussion: Previous approaches to modeling efficiency (TR79 and TR126) centered on determining the “dry” efficiency and then correcting the efficiency value for entrainment and weeping. Entrainment alone seems unlikely to be the cause of all high-rate efficiency losses. Looking back at some of the entrainment measurements with 24 inch tray spacing, there was a substantial loss of efficiency as the vapor rate was increased even though the measured entrainment rate was less than 7%. After a review of the existing database and literature, FRI can more easily determine what data might be needed to improve the FRI efficiency model and to improve tray efficiencies (at high rates).

PROSPECTUS

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