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Keynote Paper Presented at PRES17 a Process Engineering Conference on Vipertex Tubes

by vipertex on September 21st, 2017

Results from a study that evaluated the performance of Vipertex tubes have been presented at PRES17 and also been published in Chemical Engineering Transactions (CET)




VOL. 61, 2017

Guest Editors: Petar S Varbanov, Rongxin Su, Hon Loong Lam, Xia Liu, Jiří J Klemeš

Copyright © 2017, AIDIC Servizi S.r.l.
ISBN 978-88-95608-51-8; ISSN 2283-9216

Condensation and Evaporation Characteristics of Flows Inside Three Dimensional Vipertex Enhanced Heat Transfer Tubes

Results are presented here from an experimental investigation of condensation and evaporation heat transfer that compares the performance of three dimensional (3-D) enhanced heat transfer tubes to the performance of a smooth surface tube. The equivalent outer diameter of all the tubes was 12.7 mm with an inner diameter of 11.5 mm. Both the inner and outer surfaces of the 3-D tubes are enhanced by a primary enhancement and a background pattern made up by an array of dimples. Experimental runs were performed using R410A as the working fluid, over the quality range of 0.2 – 0.9. The test apparatus included a horizontal, straight test section with an active length heated by water circulated in a surrounding annulus. Constant heat flux was maintained and refrigerant quality varied.

For evaporation, the heat transfer coefficient ratio of the 3-D tubes (comparing the heat transfer coefficient of the enhanced tube to that of a smooth tube) is in the range of 1.1 – 1.80 for a mass flux rate that ranges from 80 to 180 kg/m2s. For condensation, the heat transfer coefficient ratio range is 1.1 – 1.75 for mass flux that ranges from 80 to 260 kg/m2 s. Frictional pressure drop values for the enhanced tubes show some variation. Heat transfer enhancement on the inner surface of the 3-D tubes increases the surface area and interfacial turbulence; producing flow separation, secondary flows and a higher heat flux from the wall to the working fluid.

Enhanced heat transfer tubes are important options to be considered in the design of high efficiency systems. A wide variety of industrial processes involve the transfer of heat energy during phase change and many of those processes employ old designs. These processes are ideal candidates for a redesign that could achieve improved process performance. These three dimensional enhanced tubes recover more energy and provide an opportunity to advance the design of many heat transfer products.

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