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Fouling mitigation
New tests confirm benefits of internal tube enhancement in cooling water fouling environment
Most heat exchangers that have tube-side cooling water will experience some degree of fouling . It is very important for the owner-operator to understand the factors influencing the fouling rate so that it can be managed in a way that maintains a desired heat duty over a certain time between cleanings . The use of integrally cold formed ID grooves to enhance the heat exchanger efficiency has been a common practice in the refrigeration industry for over 30 years . However , the question arises often in other industries such as power generation and petrochemical : Is it safe to use these types of enhancements without risking the possibility of increased fouling ?
By Craig Thomas , Director of Technical Sales , NEOTISS , Inc ., Rebecca Osteen , Research Engineer , Southern Company .
Two types of ID enhanced tubes that will be discussed in this article are the Helix™ tube which has spirally corrugated or indented grooves at near 90 degrees to the tube axis ; and the NEOTISS Microfin ID ( shown in the photo in combination with OD low-fin ) which has ID fins at approximately 45 degrees angle to the tube axis . The Helix tube has been used in Steam Condensing shell-side with cooling water tube side , and the HPT Fin Tube combined with Microfin ID ) has been used in a wide variety of services with the most common being refrigerant condensing shell-side with cooling water tube-side .
How does the ID enhancement benefit the process ? The spiral grooves create more turbulence inside the tube and disrupt the normal flow regime . This increases the pressure drop and friction factor at the tube wall , which in turn increases the heat transfer rate . For the HPT Fin Tube with Microfin ID the approximate expected gain on the tube-side is 80 % in heat transfer rate and 60 % in pressure drop . And for the Helix tube , it is a 30-40 % increase in both heat transfer and pressure drop . Of course , these are
NEOTISS Helix Tube™ NEOTISS HPT Fin Tube with Microfin ID .
700.00
600.00
Average Udot ( BTU / hr-ft 2 - ° F )
500.00
400.00
300.00
200.00
100.00
Tube 1 Tube 2 ( control ) Tube 3 Tube 4
0.00 |
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24-5-2023 |
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23-6-2023 |
3-7-2023 |
13-7-2023 |
23-7-2023 |
2-8-2023 |
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Table 1 . Heat transfer degradation in tested tubes . |
20 Heat Exchanger World September 2024 www . heat-exchanger-world . com