Results of a fouling study that took place with Shell Oil was presented at HTRI’s annual meeting. The study evaluated heat transfer, shear and the amount of fouling that occurred under fouling conditions using crude oil.
https://www.htri.net/events/185
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).
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.
CHEMICAL ENGINEERING TRANSACTIONS – 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
ASME Code Case 2877 details the design of heat exchangers using Vipertex® tubes.
This code case details the conditions that austenitic stainless steel welded tubes in which the external tube surface, internal tube surface, or both internal and external tube surfaces have a modified configuration. In general the following is included:
(a) The grades applicable to this include those detailed in ASTM A1098
(b) The maximum nominal diameter is limited to 1.50 in. (38 mm), and the maximum wall thickness is limited to 0.079 in. (2 mm)
(c) For determination of minimum wall thickness on textured tubing, a point-to-point micrometer shall be used. Alternately, tubing shall be supplied with plain ends and all measurements and proof testing taken in the plain end section of the tubing.
(d) The tubing shall be used for heat transfer equipment and shall be a straight length. When the tubing is used with tubesheets, the tubing shall have a plain end with untextured surfaces for the full length inserted within the tubesheet. The untextured surface would need to be both on the I.D. and the O.D.
(e) Proof tests to establish maximum allowable working pressure. The maximum allowable working pressure of any component part proof tested by this method shall be established by a hydrostatic test to failure by rupture of a full-size sample of such pressure part.
