Application of ASTM A335 P22 Serrated Fin Tubes in an Iraqi Chemical Project

In a major chemical processing facility in Iraq, YUHONG GROUP supplied custom-engineered ASTM A335 P22 serrated fin tubes for the high-temperature flue gas heat recovery system. Achieving efficient heat transfer between high-temperature flue gas and tube-side media is a critical process requirement for energy recovery and thermal efficiency optimization.

Operating under severe conditions—including elevated temperatures (500°C–600°C), high pressure, and particulate-laden flue gas—the heat exchanger tubes required high thermal efficiency, oxidation resistance, and long-term creep strength. Below is a technical overview and performance analysis of the product's application in the project's high-temperature flue gas heat recovery equipment.

The high-temperature flue gas heat exchanger in this project presented several technical challenges:

• High Gas-Side Thermal Resistance: The convective heat transfer coefficient on the flue gas side is significantly lower than that of the high-pressure liquid or steam media inside the tubes. Consequently, gas-side thermal resistance serves as the primary bottleneck restricting overall heat exchanger effectiveness.

• Severe Thermal Stress Loads: Operating flue gas temperatures consistently exceed 500°C with high internal pressure. System startup, shutdown, and load fluctuations generate substantial tangential thermal stresses across the tube bundle.

• Fouling and Ash Deposition: Industrial flue gas contains particulate matter that tends to accumulate on heat exchange surfaces, forming an insulating fouling layer that degrades heat transfer efficiency over time.

To withstand these severe operational challenges, YUHONG GROUP implemented a structural configuration pairing ASTM A335 P22 base tubing with high-frequency welded (HFW) serrated fins:

• Base Tube Material (ASTM A335 P22): Manufactured from 2.25Cr-1Mo low-alloy chromium-molybdenum steel, offering high creep-rupture strength, elevated-temperature toughness, and oxidation resistance. Rated for continuous design temperatures between 550°C and 600°C, it ensures structural safety for high-pressure media.

• Serrated Fin Geometry (HFW Process): YUHONG GROUP utilizes high-frequency resistance welding (HFW) to continuously bond serrated steel strips onto the outer wall of the base tube. The serrated cuts disrupt the gas boundary layer and induce local turbulence, significantly increasing the gas-side convective heat transfer coefficient. Furthermore, the segmented fin structure accommodates thermal expansion, relieving tangential stress and preventing fin cracking or weld detachment.

• Enhanced Heat Transfer Efficiency: Compared to bare tubes, the fins expand the external heat transfer surface area. Compared to solid fins, the serrated profile induces stronger fluid turbulence, further reducing gas-side film thermal resistance.

• Superior Fouling Resistance: The serrated geometry reduces the dead-wake area behind the tubes where ash typically accumulates, lowering dust deposition rates and maintaining steady thermal performance when paired with soot blowers.

• High Structural Reliability: YUHONG GROUP maintains strict quality control over the high-frequency welding process, establishing a metallurgical bond with virtually zero contact thermal resistance capable of enduring severe cyclic thermal shock.