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Queen Mary University of LondonQueen Mary University of London
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School of Engineering and Materials Science
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PhD Thesis: Filmwise condensation of high velocity downward flowing steam on a bundle of horizontal tubes.

Author: BEECH, Philip

Year: 1995

Supervisor(s): John Rose

The thesis describes an experimental study performed at the Harwell Laboratory, Oxfordshire, into condensation of vertically downward flowing steam at slightly above atmospheric pressure on a horizontal staggered tube bundle, with and without simulated inundation. The experimental bundle comprised ten rows of condensing tubes preceded by three rows of dummy tubes. Four inundation tubes, located above the dummy tubes could be supplied with condensate to simulate inundation in larger bundles. The nickel plated copper tubes were 252 mm long (180 mm condensing length), 14 mm o.d. and 9.88 mm i.d. These were insulated from the body of the test section. The tubes were arranged in a staggered layout with a pitch-to-diameter ratio of 20/14. At least one tube in each row was instrumented with four embedded wall thermocouples. The steam pressure upstream of the bundle and the pressure drop across each row were measured. The heat flux was calculated from the cooling water flow rate and temperature rise. The steam mass flow rate was measured by an orifice plate. Experiments covered the following parameter ranges: steam approach velocity (based on maximum flow area) 6.0-18.4 m/s, first row condensate temperature difference 5.5-20 K and heat-flux 290-520 kW/m2. Using simulated inundation, a bundle having approximately twenty equivalent tube rows could be represented.

This work was preceded by that of Nobbs [1975] using a single active condensing tube within a dummy bundle supplied with simulated inundation and Michael [1988] who used the Harwell facility prior to the addition of the simulated inundation section (bundle instrumentation has also subsequently been upgraded). Michael reported steam heat-transfer coefficients up to a factor of two higher than those of Nobbs, suggesting the discrepancy between the data may be due to different bundle configurations. The present results are aimed at resolving these discrepancies, whilst expanding the range of pertinent parameters.

The present data are in fair agreement with the theoretical predictions of Shekriladze and Gomelauri [1966]. The data of Nobbs indicate lower coefficients, whilst Michael's yield coefficients somewhat higher than the theoretical predictions.