Heat Transfer Enhancement
Manufacturers of these tubes can properly optimize the heat transfer vs pressure drop effects and provide an optimum solution. Boiling and condensing enhancements( Figures, 1b and 1c) increase the heat transfer coefficient substantially above the level of a conventional low fin tube, allowing the operation of enhanced shell and tube heat exchangers at very low cold-end approach temperatures. The increase in heat transfer coefficient is in the range of 1.5-20 for boiling and 2-5 for condensing. The best results can be achieved at low heat fluxes and small temperature differences. As an example of the total benefit, in the propane chiller in an LNG precooling refrigeration system, the overall surface area, and therefore the tube length, can be decreased by up to 60 % and the total heat exchanger weight by 55 %, by using a dual-enhanced boiling tube [ Ref. 2 ].
Available materials and tube sizes Dual enhanced tubes are available in the commonly used tube sizes- tube outside diameters in the range of 5 / 8-1”( 15-25 mm), and materials- – carbon, low temperature carbon steels including 3.5 % Ni, copper and copper alloys, stainless steel and titanium. The testing of low-fin and dual enhanced tubes during fabrication follows the same principles as plain tubes. Destructive testing is done in accordance with the relevant standards by eddy-current or pressure testing, and even field testing with internal eddy current testing is feasible.
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Upcoming in this series In upcoming articles in this series we will look at applications of boiling and condensing enhancement and show case studies which quantify the benefits for typical applications.
References [ 1 ] Principles of Enhanced Heat Transfer, 2ndEd, Ralph L. Webb & Nae-Hyun
Kim, Taylor & Francis 2005.
[ 2 ] Wieland Website with references. https:// www. wieland. com / en / solutions / energy / process-industry.
About the authors
Himanshu Joshi retired from Shell in 2021 after 34 combined years with ExxonMobil and Shell, during which he specialized in heat exchangers and fouling. He was part of a team that was granted a patent related to fouling deposit analysis at ExxonMobil, and led applied fouling R & D projects at both companies. He has made several presentations about the field aspects of fouling and fouling mitigation, and deployed many mitigation technologies in the field. He can be reached by email at alph. hmj @ gmail. com.
Lou Curcio has over 30 years of experience in design, troubleshooting and repair of all types of heat exchangers. Leader of technology development projects and advisor for ExxonMobil’ s global manufacturing teams. Co-inventor of two U. S. patents and co-author of papers on enhanced heat transfer and fouling of heat exchange.
Thomas Lang is Manager Product Management- Process Industry, at Wieland Thermal Solutions Ulm, Germany. He has over 30 years’ experience in technical marketing and business development of enhanced heat transfer solutions for various applications and industries, primarily for the oil and gas, petrochemical, refining, chemical and power. Supporting HTRI in several roles( communication and technical committee) he is since August 2024 member of the HTRI board. He received his diploma in mechanical engineering( Dipl.-Ing.) from the University of Stuttgart, Germany, and a Master of Science in Civil Engineering from the University of Colorado at Boulder- Colorado, USA.
What differentiates HMT from others
Carbon Steel, Alloy Steel & Stainless Steel from same mfr. Capability to mfr. st. length tubes upto 34 Mtrs. U-Tubes with max. hydro test pressure @ 700 Kg / CM 2 Special grades with quick delivery | SA334 Gr. 3, SA213 T5 / T9 / T91
Duplex & Super Duplex, TP310 / TP321H / TP347H / TP405 / TP410
Website: www. hmtl. in Email: info @ hmtl. in, mkt @ hmtl. in, exports @ hmtl. in Mobile: + 91-90165 49266, Tel.: + 91 90812 55991 / 92 / 93 www. heat-exchanger-world. com