Publications

This article was presented at the November 9th, 1999 "Latest Advances in Offshore Processing" conference in Aberdeen, Scotland. Heat exchangers are usually classified by the compactness factor in m²/m³ and it is generally accepted that values greater than 700 m²/m³ characterize compact equipment. Although shell-and-tube exchangers can have high compactness factor, compact heat exchangers are often referred to as non-tubular devices. This paper describes an advanced shell-and-tube heat exchanger using twisted tubes. Recent advances in the range of design and operational reliability have made twisted tube heat exchangers attractive in various industries, including offshore application. Taking into account size and convenience considerations, these exchangers can be cost-effective in a wider range of applications than the niches currently being used in the process industry.

Conventional baffled shell-and-tube exchangers, while having an excellent record of acceptance and functionality, have some notable limitations. In particular, the shell-side path is wasteful on pressure drop, limits maximum thermal effectiveness and encourages dead spots where fouling or corrosion may occur. This paper describes an advanced shell-and-tube design, known as the Twisted Tube® Heat Exchanger, which is inherently able to overcome these limitations in addition to providing the further advantages of tube-side enhancement and good tube support to reduce susceptibility to vibration. The paper compares the Twisted Tube ® exchanger with conventional and advanced designs.

This paper describes testing of advanced shell & tube design with Twisted Tube® technology. Its performance has been tested under single-phase, fully developed, transition flow conditions. Subject to design constraints and based on specific optimization requirements, several configurations were tested, each test examining heat transfer and pressure drop for the particular heat exchanger. It was shown that overall heat transfer and pressure drop increase with a smaller tube twist pitch to diameter ratio, and that these exchangers have specific advantages and characteristics, previously open only to plate exchanger users. Twisted tubes increase the level of mixing and promote turbulence in the low Reynolds number range, on both tube-side and shell-side of the tubes.

Driven by competitive market forces and stricter environmental compliance, the whole question of chemical plant energy consumption is receiving renewed attention with an eye toward: process changes through the use of new heat transfer technologies, heat recovery and pinch technology, accurate fouling prediction and reduction, increasing plant throughput.

This paper will re-examine the basic principles of economical heat transfer as it relates to the issues listed.

This article appeared in the October 1997 issue of The International Journal of Hydrocarbon Engineering, and examines the basic principles of economical heat recovery, with relation to both overall plant energy efficiency and the application of pinch technology, which assures maximum energy recovery. Considerations are given to overall heat transfer, pressure drop, velocity restrictions, and physical properties that affect heat exchanger performance. These topics are currently extremely relevant because refiners are improving process operations to remain competitive in the global marketplace. 

This article was printed in Hydrocarbon Engineering magazine dated April 1999 and describes the flow of non-Newtonian fluids in heat exchangers. For many years, Hook's law for solids and Newton's law for liquids were considered universal. In classical mechanics, material properties were considered known when either viscosity or modulus of elasticity were given; the basic 'constitutive equations' governing the behavior of each small material element were known. Practical analysis often involved coupling these equations with the momentum equation and applying them to the increasingly complicated flows or deformations. However, dealing with solids and liquids seemed deceptively simple. As nature is never so straightforward, this was a gross oversimplification of a complex situation. In virtually all industries including petroleum, foods, pharmaceuticals, minerals, etc, many materials cannot be strictly classified as liquids or solids. The science that deals with these complex materials is called 'Theology', the study of the deformation and flow of matter.

This paper was prepared for presentation for the CE Expo Conference in Houston, Texas in June, 1999. Today's low energy costs result in many projects for energy reduction being insufficiently attractive to justify their installation. The payback times for such projects may be unattractive due to the need for piping modifications to install new exchanger area. This paper presents a simplified analysis of a project to install high performance tube bundles into existing shells with no piping modifications. It uses a crude unit heat train as an example. It further introduces a new Pinch concept which is used to identify the optimum choice of exchanger bundles to be replaced.

This article appeared in the September 2006 issue of The International Journal of Hydrocarbon Engineering, it discusses the application of Twisted Tube® technology in kettle reboiler revamps at the Ju'Amyad gas plant.

This paper, presented in 2007 at the 7th International Conference on Heat Exchanger Fouling Mitigation and Cleaning, discusses design approaches to evaluate twophase flow conditions and design exchangers to minimize fouling. Such design approaches may not be optimum for heat transfer and pressure drop considerations; however, it will minimize fouling and localized corrosion. The paper focuses on improved design of feed/effluent exchangers with tube side flows and reboilers for minimizing shell-side fouling and a case study is presented. The result is lower lifecycle ownership cost of the exchanger.