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ISSN Online: 2377-424X

International Heat Transfer Conference 12
August, 18-23, 2002, Grenoble, France

Experimental Study of Separation in Reflux Condensers

Get access (open in a dialog) DOI: 10.1615/IHTC12.5500
6 pages

摘要

Any partial condensation process may be used to separate vapour mixtures as a consequence of their different volatilities and will produce a vapour rich in the more volatile component. The separation is improved in a reflux condenser, which is a cooled vertical tube with the vapour stream in counter-current flow to its condensate. The separation is better than with co-current flow because the falling condensate is exposed to the entering vapour producing a condensate that may become as lean as possible in the more volatile component.

The process is complicated because it is both the mass transfer rate processes and the relative direction of the condensate flow that determine the extent of the separation. Mass transfer resistance can arise on both the vapour and condensate sides. Locally, the surface composition will be determined by equilibrium and a diffusion process will take place from bulk gas phase to interface and from interface into the condensate. There is no clear indication in the literature as to the relative importance of the mass transfer resistances on these two sides. The evolving behaviour will also depend on the relative flow directions of vapour and condensate, the latter determined by gravity and vapour shear.

This paper describes a careful experimental programme carried out to measure the performance of a reflux condenser in the separation of methanol-water mixtures at a range of vapour compositions, reflux ratios, temperature driving force distributions and pressure drops. These experiments were carried out in a single tube of 3 m length and 25.4 mm inside diameter with measurement of wall temperature. They give information that allows firm conclusions to be reached as to the controlling mechanisms and the degree of separation that can be achieved. The conclusions of this paper are exploited in Webb and Al-Shammari, (2002).