Heat Transfer Enhancement
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Table 1. Comparison of Plain Tubes vs hiTRAN inserts in a Wet Crude Preheat Train.( Case Study 1)
No of shells
Tube Bundle
Empty tube
20 shells in 2 trains( 2 series; 5 parallel) hiTRAN ® design
8 shells in 2 trains( 1 series; 4 parallel)
Tubes [-] |
1550 |
1366 |
Tube size |
25.4 mm × 6.1 m |
25.4 mm × 4 m |
Passes [-] |
4 |
2 |
Total area [ m 2 ] |
14453 |
3267 |
Heat Exchanger Performance Tube side Pressure Drop [ kPa ] |
109 |
100 |
Shell side HTC [ W / m 2 K ] |
388 |
463 |
Tube side HTC [ W / m 2 K ] |
64 |
641 |
Tube side Reynolds Number [-] |
~ 800 |
~ 540 |
Overall HTC [ W / m 2 K ] |
45 |
208 |
Exchanger heat duty [ MW ] |
13 |
13 |
Total flow path length [ m ] / residence time [ s ] |
48 / 56 |
8 / 13 |
Exchanger purchase & installation costs [ USD ] |
9 200 000 |
4 600 000 |
retrofit is of an existing ethylene vaporiser that was not delivering its required heat duty is shown in the case study below, with a summary in Table 2.
Case Study 2 An existing ethylene vaporizer was not delivering its required duty because a large part of the tube length was predicted to be in film boiling. In this condition, a stable vapor layer forms at the tube wall, liquid wetting is lost, and wall-side heat transfer drops sharply. The result was inefficient vaporization, limited ethylene throughput and an outlet condition close to saturation, providing little or no superheat margin for downstream equipment. The solution was to retrofit hiTRAN on the tube side to change the two-phase flow behaviour rather than replace the exchanger. The elements promoted better liquid distribution along the tubes, enhanced convection in the sub‐cooled region, and helped maintain a more consistent wetting of the tube wall. At the same time, they helped to suppress extended film boiling and reduce mist carry‐over towards the outlet, so more of the tube surface operated in efficient boiling regimes. With hiTRAN installed, the tube-side heat transfer increased substantially, allowing a 45 % increase in vapour throughput and heat duty to increase by 357 kW. The outlet condition improved from saturated vapour at about −1 ° C to approximately 30 ° C superheated. This meant the unit could deliver higher throughput and duty with a reliable superheat margin, all while remaining within the available tube-side pressure drop.
What to consider in new and existing applications When considering hiTRAN, the best starting point is not the insert itself but the real tube-side limitation in the duty. For new applications, key questions include:
• Is the tube side controlling the overall duty?
• Is the plain-tube design drifting toward too many passes, too many shells, or too much plot space?
• Would a lower-pass, more compact design have a cost, weight or layout benefit?
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Table 2. Comparison of Plain Tubes vs hiTRAN inserts in an Ethylene Vaporizer.( Case Study 2)
Plain empty |
hiTRAN ®( after retrofit) |
Flow rate [ kg / sec ] |
14.5 |
21.1 |
Temp. in / out [° C ] |
-100 /-1( sat.) |
-100 / 30( superheated) |
Pressure in / out [ bar ] |
40 / 39.93 |
40 / 39.74 |
Overall HTC [ W / m 2 K ] |
613 |
2390 |
Heat duty [ kW ] |
261 |
618 |
18 Heat Exchanger World October 2026 www. heat-exchanger-world. com