Heat Exchange Tube FAQ - Technical Questions Answered

Smooth tubes are typically 10-20% cheaper than internally grooved tubes of the same diameter and wall thickness. For applications with moderate heat transfer requirements, smooth tubes provide a more economical solution without compromising system performance. For high-efficiency applications, we recommend evaluating the overall system cost-effectiveness, as internally grooved tubes can reduce the size and material usage of heat exchangers.

Our coil products are wound on sturdy steel spools with proper tension control to maintain coil integrity. Each coil is secured with multiple circumferential straps and wrapped with moisture-proof polyethylene film and woven fabric. The spool design supports the coil weight and prevents deformation during handling and transportation. For large coils, we use wooden frames or pallets to provide additional protection.

Our internal wall residual carbon content is controlled at ≤0.02 g/m², which meets industry standard requirements for AC applications. This low residual level prevents capillary tube blockage and ensures long-term system reliability. For applications requiring stricter control, we offer enhanced cleaning processes upon request, achieving ≤0.01 g/m².

Yes, we offer customized non-standard outer diameters to meet specific application requirements. Custom sizes may require specialized tooling and are subject to minimum order quantities. Please provide your desired diameter, wall thickness, and tolerance requirements to our engineering team, and we will evaluate feasibility and provide a quotation. Typical lead time for custom sizes is 3-4 weeks.

In a dry expansion evaporator, refrigerant flows inside the tube and gradually evaporates along the tube length. The groove design must promote nucleate boiling while handling two-phase flow and increasing vapor quality. In contrast, a flooded evaporator has refrigerant on the shell side and water inside the tube, requiring enhanced boiling on the outer diameter. DX tubes focus on internal groove optimization for flow boiling, while flooded tubes typically have external enhancement for pool boiling heat transfer.

Our tubes have tight wall thickness tolerances of ±0.02 mm, ensuring uniform expansion into the tube sheet without excessive thinning or cracking. Consistent bottom wall thickness across the entire tube circumference and length guarantees a reliable mechanical rolled joint. For high-pressure applications, we recommend our O-annealed tubes, which provide optimal ductility for expansion. The groove geometry is designed to maintain structural integrity during expansion without groove collapse.

Compared to traditional HFCs, low GWP refrigerants such as R290 have different thermophysical properties and lower mass flow rates. For R290 and similar hydrocarbons, we recommend groove designs with lower fin heights and optimized helix angles to maintain efficient heat transfer under reduced refrigerant charge. Kaineng's engineering team can develop custom groove profiles based on your specific low-charge system requirements. We have successfully supplied DX tubes for R290 heat pump projects with a 40% reduction in charge.

Yes, we offer several anti-corrosion treatment options depending on the application environment. For seawater or high-humidity applications, we can apply a specialized epoxy coating on the outer surface of the tube. To improve corrosion resistance in harsh water conditions, we also offer tin plating services. Please specify your water chemistry and operating conditions when inquiring, and our technical team will recommend the most suitable protective treatment.

We do not recommend direct replacement. Heat pump evaporator tubes are specifically designed for low evaporation temperature conditions (-10°C to -25°C), featuring optimized groove geometry and thicker anti-freeze walls. Standard AC inner groove tubes are optimized for higher evaporation temperatures (typically 5°C to 10°C). When used in heat pump applications, especially in cold climates, they may reduce efficiency and increase the risk of freezing.

R32 operates at higher pressures than R410A, and as a mildly flammable (A2L) refrigerant, safety considerations are paramount. For R32 heat pump systems, we recommend our specially optimized groove profiles to balance heat transfer performance and reduce refrigerant charge. The tubes are manufactured with enhanced wall thickness consistency to withstand higher operating pressures. Additionally, the groove geometry is fine-tuned according to the thermophysical properties of R32 to maximize efficiency under low ambient temperatures.