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Bubble compression and condensation in single component co-current downflow

University of British Columbia

In an investigation of the process termed hydraulic vapour compression (HVC), a photographic study of bubble compression and condensation rates in single component co-current downflow has been performed. Supplemental to the photographic study, measurements of the deliverable mass flowrates of the HVC process were also carried out. The downward flow of a gas and liquid mixture, as occurs in the HVC process, results in the compression of the gas phase because of the increasing hydraulic pressure. Bubble compression heating provides the driving temperature difference for both heat and mass transfer to occur. The minimization of the transfer processes is desirable to ensure a high compression efficiency. Experiments were carried out using near saturated Freon-11 in a 2.54 cm I.D., 1.7 m long glass downcomer. Bubbles were filmed during travel along the downcomer. Histories of the decrease in individual bubble size were determined from silhouette traces obtained from sequenced single frames selected from the exposed films. Bubble volumes and surface areas were inferred by numerically revolving digitized images of the traces about their principal centroidal axes. The inferred volumes and surface areas provided the basis upon which heat and mass transfer rates were calculated. Delivered vapour mass flowrates were measured by hot film anemometry. Results showed that mass condensation rates increased along the length of the downcomer. Local external Nusselt numbers used to characterize the transfer processes at the bubble wall, ranged from 0.1 to 16. The deliverable mass flowrates achieved by the HVC process were found to be comparable to those produced by the well known process of hydraulic air compression.

Text

2010-07-08

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http://hdl.handle.net/2429/26223

Mechanical Engineering

University of British Columbia

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