Heat Transfer Enhancement
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Get more out of your heat exchangers with heat transfer enhancement: Part 8 – Introduction to hiTRAN wire matrix tube inserts
When tube-side performance limits a heat exchanger, adding more surface area is not always the best answer – Refer to Part 2 of this series for an understanding of“ controlling resistance”. In these cases, the real constraint is inside the tube: a low velocity boundary layer at the tube wall, weak radial mixing, low wall shear, or a two-phase flow regime that reduces heat transfer. Inserts that improve tube side heat transfer are one proven solution to this problem.
By Nathan Hill, Technical Sales Engineer, Matthew Keen, Sales Engineer, CALGAVIN Ltd, Lou Curcio, Heat Transfer Advisor, Himanshu Joshi, Heat Exchanger Specialist
Tube inserts are often described as either passive or active. Active inserts rely on motion such as vibration, pulsation or an applied field to modify the flow and enhance heat transfer, making passive inserts the more common practical choice in process exchangers. One example of active tube inserts is rotating twisted-tape inserts where a twisted tape— normally a passive swirl generator— is allowed to rotate inside the tube, either driven by the fluid flow or by an external mechanism. This rotation significantly increases swirl intensity, disrupts the thermal boundary layer, and boosts mixing. Passive inserts improve heat transfer through their geometry alone by promoting swirl, radial mixing and boundarylayer disruption, without any external energy input. For example, wire matrix tube inserts provide better radial mixing and improve tube side heat transfer. One such insert is hiTRAN from CALGAVIN. Installed on the tube side of tubular exchangers, it is designed to make better use of the available pressure drop to achieve higher heat transfer, favourable wall conditions( temperature, shear, residence time), and more reliable operating performance in both new and existing equipment. The enhancement benefits of hiTRAN can be used for different objectives. In some cases, the goal is a smaller and lighter new heat exchanger. In others it is to recover more heat duty, reduce vapour carryover, suppress film boiling, improve flow distribution, mitigate waxing, or stabilise operation in an existing unit. hiTRAN can be applied in shell-and-tube exchangers, including straight-tube and U-tube configurations, in air-cooled heat exchangers, and in other tubular process equipment where the tube side is the controlling resistance.
What hiTRAN changes inside the tube hiTRAN consists of a central core wire with a series of loops that contact the tube wall. By varying loop density, wire size and element geometry, the insert can be tailored to the service, the fluid properties and the allowable pressure drop. Its benefit comes from the flow pattern it creates. Rather than allowing a stagnant, thermally resistant boundary layer to develop at the wall, hiTRAN continuously promotes radial mixing between the fluid near the wall and the bulk flow. This results in:
Figure 1. Installing hiTRAN inserts. Image courtesy of CALGAVIN Ltd.
16 Heat Exchanger World October 2026 www. heat-exchanger-world. com