Heat Exchange Tube FAQ - Technical Questions Answered

The fins are mechanically rolled from the base tube material, providing good mechanical strength suitable for normal operation and handling. However, they can be bent by excessive force or improper tools. During chemical cleaning, use recommended inhibitors and avoid acid concentrations that may attack the fin base. For mechanical cleaning, we recommend using a soft brush instead of a wire brush. If fins are accidentally damaged, the local performance impact is usually minimal, and severely damaged tubes can be replaced individually.

Yes, TC series externally finned tubes are well suited for ammonia (R717) condensing systems. However, material selection should be carefully considered. For ammonia systems, we recommend CuNi10Fe1Mn (copper-nickel) alloy instead of pure copper or TP2, as copper-nickel alloy offers better corrosion resistance in ammonia environments. The fin geometry can also be optimized for the thermophysical properties of ammonia. Please consult our engineering team with your specific ammonia condensing requirements.

The most common connection method for condenser tubes is mechanical tube expansion (rolling), where the tube end is mechanically expanded into the tubesheet to form a tight sealed joint. For high-pressure applications, we recommend welded joints or a combination of expansion plus seal welding. Explosion-bonded tubesheet cladding with tube expansion is also suitable for severe service conditions. The fin structure does not affect the tube end connection, as the finned section stops before the tube end, leaving a smooth plain section for tubesheet insertion.

In a flooded evaporator, the tubes are completely submerged in liquid refrigerant or coolant, and boiling occurs directly on the tube surface. In a falling film evaporator, the liquid is distributed as a thin film that flows along the tube surface, and evaporation occurs from the film. This key difference drives distinct tube surface requirements: flooded tubes require enhanced boiling surfaces (porous, fins) to promote nucleate boiling, while falling film tubes require surfaces that promote uniform film spreading and maintain film stability. Falling film designs also typically require less refrigerant charge and provide better temperature approaches.

Uniform film distribution is achieved through a combination of proper liquid distribution system design and tube surface optimization. Our tubes feature surface structures that promote rapid and uniform liquid spreading around the tube circumference. At the system level, proper inlet distributor design, tube spacing selection, and liquid loading per tube are critical. Kenergy provides tube products and distribution design recommendations to ensure optimal wetting. We also offer customized surface patterns to enhance film formation characteristics in challenging applications.

The cleaning method depends on the type of fouling. For soft and organic fouling, chemical cleaning with appropriate detergents or mild acids is effective. For hard mineral scale, controlled acid cleaning with inhibitors is recommended. For tubes with smooth or low-fin surfaces, mechanical cleaning with soft brushes or high-pressure water jets can also be used. Our anti-fouling surface treatments significantly reduce cleaning frequency. We recommend establishing a regular inspection and cleaning schedule based on your specific water chemistry and operating conditions.

Yes, falling film evaporator tubes are widely used in multi-effect distillation (MED) and mechanical vapor compression (MVC) seawater desalination plants. For seawater desalination, we recommend CuNi10Fe1Mn (90/10 copper-nickel) due to its excellent corrosion resistance in seawater environments. For higher temperatures or more aggressive conditions, 316L stainless steel or titanium (Grade 2) are also available. The tube surface structure can be optimized to enhance wetting and heat transfer for seawater. Kenergy has extensive experience supplying tubes for seawater desalination projects worldwide.

Compared to stainless steel, copper has significantly higher thermal conductivity (~400 W/m·K) (316L is ~15-20 W/m·K). However, stainless steel is chosen for applications where corrosion resistance, cleanliness, or mechanical strength takes priority over thermal performance. In many chemical, pharmaceutical, and food applications, copper is unsuitable due to corrosion or contamination issues. The lower thermal conductivity is often compensated for by using thinner walls, enhanced surfaces (fins/grooves), or increasing flow velocity. Despite the thermal conductivity trade-off, total system cost and reliability in corrosive environments often favor stainless steel.

For seawater cooling service, we do not recommend 304 because it is prone to chloride pitting and stress corrosion cracking in seawater. 316L has moderate resistance and, with careful design, is suitable for low-temperature seawater applications. For improved reliability and longer service life, especially in warm or polluted seawater, 2205 duplex stainless steel is preferred due to its higher pitting resistance equivalent (PRE) and excellent resistance to chloride stress corrosion cracking. For the most demanding marine environments, super duplex 2507 or titanium is recommended. Please contact our corrosion engineering team for specific material recommendations based on your seawater temperature and chemical composition.

No, expanding stainless steel tubes requires different parameters compared to copper. Stainless steel has higher yield strength and work-hardening characteristics, requiring greater expansion force and careful control of the expansion ratio. Specialized rolling tools with proper lubrication are needed to prevent galling and ensure consistent joint quality. For thick-walled stainless steel tubes or high-pressure applications, hydraulic expansion or explosive expansion may be preferred over mechanical rolling. Kenergy can provide detailed expansion recommendations for each stainless steel grade and wall thickness combination to ensure leak-tight tube-to-tubesheet joints.