Heat Exchange Tube FAQ - Technical Questions Answered

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.

Yes, we offer complete tube bundle manufacturing services, including tubesheet drilling, tube insertion, expansion or welding, and hydrostatic testing. We can provide partial assemblies (tubes cut to length, tubesheets drilled only) or fully assembled bundles ready for installation into the heat exchanger shell. This integrated service ensures consistent quality, shortens your manufacturing lead time, and eliminates the risk of tube-to-tubesheet joint failure. Please share your heat exchanger drawings with our team for a complete quotation.

Internally grooved tubes are typically 10-20% more expensive than smooth tubes of the same diameter and wall thickness. However, because they provide 30-50% higher heat transfer efficiency, you can use fewer tubes or a smaller heat exchanger to achieve the same thermal performance, potentially reducing overall system costs. The return on investment is particularly attractive for high EER and inverter AC products.

R32 operates at higher pressures than R410A and R22. For R32 applications, we recommend optimized groove designs with slightly increased fin height and modified helix angles to enhance heat transfer while maintaining mechanical strength under high pressure. Kenergy has developed specific R32-optimized tube designs, verified through extensive testing.

Yes, with specific design considerations. CO₂ transcritical systems operate at extremely high pressures (up to 130 bar). We offer enhanced internally grooved tube designs for CO₂ applications, with thicker walls and groove geometries. These tubes are made from high-strength copper alloys to ensure safe and reliable operation under transcritical conditions.

For standard sizes and groove patterns, our minimum order quantity is typically 500 kg per specification. For custom groove designs or non-standard diameters, the MOQ is 1000 kg. Sample quantities (under 50 kg) are available for qualification testing and prototype development. Please contact our sales team with your specific requirements for detailed MOQ information.