The Effects of Vapour Shear and Inundation on Roped Tubes

[摘要] This investigation is concerned with the effects of both vapour shear and inundation on the performance of the overall heat transfer coefficient of plain and roped tubes. A series of experiments were conducted using a specially designed test condenser and three types of tubes to initially determine the effect of steam velocity and tube geometry on the overall heat transfer coefficient. Subsequent tests were performed to investigate the combined effects of vapour shear and inundation on bundles of condenser tubes. The main experimental variables in the tests were steam velocity, cooling water velocity and the number of equivalent tubes in a vertical array. The results of the vapour shear tests conclusively showed that as the velocity of steam increased so did the amount of heat transferred by all of the three types of tubes. These tests also determined that the geometry of a tube bundle (i.e. staggered or in-line configurations) made little or no difference to the overall heat transfer coefficient. The multi-tube experiments confirmed that inundation reduced the heat transfer in condensers and showed that the effect of inundation was moderated through the use of a higher steam velocity. This result was convincingly shown for bundles of 2-start roped tubes but was less apparent for similar bundles of both plain and 6-start roped tubes. In all of the above experiments the roped tubes were found to consistently outperform the equivalent plain tubes with respect to the amount of heat transferred. In addition to the experimental work, two computer programs were used to predict the effects of vapour shear and inundation on both single tubes and tube bundles. The theoretical predictions were compared with the test results and very good agreement was found for the plain tube simulations. The predictions of the roped tube simulations were judged to be less accurate than those of the plain tube, but still good considering the complex hydrodynamic and thermal processes associated with roped tubes.

[发布机构] University:University of Glasgow

[关键词] Mechanical engineering