Stainless Steel Coil Tube for Heat Exchange & Cold Water Systems
Product Code: JX-CT-397 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
1. Product Overview
The Stainless Steel Coil Tube (盘管 / Coil Tube) is a precision-engineered tubular product formed into a helical or spiral geometry, designed specifically for heat exchange applications and cold water distribution systems. Unlike conventional straight tubing, coil tubes offer significantly enhanced surface-area-to-volume ratios, thereby maximizing thermal transfer efficiency within compact installation footprints. This product line addresses critical engineering challenges identified in the study of "Cold Water Balance Based on Heat Transfer Characteristics of Cold Coil Tubes and Cold Water System Solutions", providing a comprehensive solution for maintaining thermal equilibrium in chilled water loops, HVAC systems, and industrial process cooling circuits.
Wenzhou Jixing Metal Materials Co., Ltd. leverages decades of metallurgical expertise to produce coil tubes that combine superior corrosion resistance, mechanical integrity, and thermal conductivity — making them the preferred choice for demanding environments where fluid-structure interaction and long-term reliability are paramount.
2. Material & Properties
2.1 Base Material Composition
The primary alloy grades offered include Austenitic Stainless Steels conforming to ASTM and EN standards:
- 304 / 1.4301 (AISI 304): General-purpose grade with excellent weldability and moderate corrosion resistance. Contains 18–20% Chromium (Cr) and 8–10% Nickel (Ni).
- 316 / 1.4401 (AISI 316): Enhanced chloride resistance grade with 2–3% Molybdenum (Mo) addition. Ideal for coastal, chemical, and food-grade applications.
- 316L / 1.4404 (AISI 316L): Low-carbon variant (C ≤ 0.03%) designed for welding-intensive applications to prevent intergranular corrosion.
- 321 / 1.4541 (AISI 321): Titanium-stabilized grade offering superior resistance to sensitization at elevated temperatures (up to 870 °C).
2.2 Key Mechanical & Physical Properties
| Property | 304 / 1.4301 | 316 / 1.4401 | 316L / 1.4404 |
|---|---|---|---|
| Tensile Strength (Ultimate, UTS) | ≥ 515 MPa | ≥ 515 MPa | ≥ 485 MPa |
| Yield Strength (0.2% Proof) | ≥ 205 MPa | ≥ 205 MPa | ≥ 170 MPa |
| Elongation (A50) | ≥ 40% | ≥ 40% | ≥ 45% |
| Thermal Conductivity (at 20 °C) | 16.3 W/(m·K) | 16.3 W/(m·K) | 16.3 W/(m·K) |
| Specific Heat (at 20 °C) | 0.50 J/(g·K) | 0.50 J/(g·K) | 0.50 J/(g·K) |
| Density | 7.93 g/cm³ | 8.00 g/cm³ | 8.00 g/cm³ |
| Maximum Service Temperature | 870 °C | 870 °C | 870 °C |
| Corrosion Resistance (Pitting) | Good | Excellent (PREN ≥ 24) | Excellent (PREN ≥ 24) |
2.3 Surface Finish Options
- Pickled & Passivated (2B Finish): Standard mill finish with a chromium oxide passive layer for general corrosion protection.
- Electropolished (Ra ≤ 0.4 μm): Electrochemical polishing for sanitary and pharmaceutical applications; removes surface contaminants and enhances passive film integrity.
- Mirror Polished (Ra ≤ 0.1 μm): High-lustre finish for decorative or specialized optical applications.
3. Specifications
3.1 Dimensional Parameters
| Parameter | Range / Value | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 3 mm – 108 mm | ASTM A554 / EN 10217-7 |
| Wall Thickness (WT) | 0.3 mm – 6.0 mm | ASME B36.19M |
| Coil Pitch | 5 mm – 50 mm (customizable) | Per customer specification |
| Coil Diameter (Bundle) | 50 mm – 2000 mm | Per customer specification |
| Tube Length (per coil) | 1 m – 50 m | Per customer specification |
| Dimensional Tolerance (OD) | ±0.05 mm – ±0.15 mm | EN 10217-7 Class 1 |
| Dimensional Tolerance (WT) | ±10% (min ±0.05 mm) | ASTM A554 |
| Maximum Operating Pressure | Up to 4.0 MPa (40 bar) | ASME B31.3 |
| Working Temperature Range | −196 °C to +450 °C | Per alloy grade |
3.2 Geometric Configuration Options
- Spiral Coil (平面螺旋盘管): Single-plane helical winding; suitable for shell-and-coil heat exchangers and compact radiators.
- Helical Coil (螺旋盘管): Three-dimensional helical geometry; optimized for forced-convection air-side heat exchange.
- U-Tube Bundle (U型管束): Pre-formed U-bend configurations for fixed tubesheet heat exchangers.
- Coil-in-Coil (盘管套盘管): Nested double-coil configuration for direct fluid-to-fluid heat recovery.
4. Manufacturing Process
4.1 Process Flow
- Raw Material Inspection: Incoming stainless steel strip or seamless tube undergoes spectroscopic verification (OES analysis) to confirm chemical composition compliance with the specified grade.
- Cold Rolling & Annealing: Strip is cold-rolled to target thickness with intermediate annealing cycles to maintain ductility and achieve the desired grain structure (austenitic FCC crystal lattice, ASTM E10 grain size 1–8).
- Precision Slitting & Straightening: The rolled product is slit to exact width and straightened to within ±0.1 mm/m flatness tolerance.
- Coil Forming (盘管成型): Using CNC-controlled coiling machines with variable-diameter tooling, the tube is cold-formed into the specified helical or spiral geometry. Real-time monitoring ensures uniform pitch and minimal residual stress.
- Stress Relief Annealing: Post-forming annealing at 850–1050 °C in a protective atmosphere (nitrogen or argon) to eliminate cold-work hardening, restore full ductility, and relieve internal stresses that could cause springback or distortion during service.
- Pickling & Passivation: Immersion in a mixed acid bath (HNO₃ + H₃PO₄) to remove oxide scale, followed by passivation to establish a chromium-rich protective oxide layer (Cr₂O₃, typically 2–5 nm thick).
- Hydrostatic Testing: Each coil is pressure-tested at 1.5× the maximum operating pressure to verify weld integrity and detect porosity or micro-cracks.
- Final Dimensional & Visual Inspection: Coordinate Measuring Machine (CMM) verification of coil geometry; dye-penetrant testing (PT) per ASTM E709 for surface defect detection.
4.2 Key Process Advantages
- Cold forming without welding: Eliminates weld-induced sensitization and reduces risk of intergranular corrosion.
- CNC precision control: Ensures repeatable pitch accuracy of ±0.5 mm across the entire coil length.
- Atmospheric annealing: Prevents carbon pickup and maintains the low-carbon composition critical for 316L applications.
5. Applications
5.1 Heat Exchange Systems
- Shell-and-Coil Heat Exchangers: The coil serves as the tube-side or shell-side heat transfer element in compact exchangers for process heating/cooling.
- Air-Source Heat Pumps: Evaporator and condenser coils leveraging the high surface-area ratio for efficient latent and sensible heat transfer.
- Plate-and-Frame Alternative Systems: Coil configurations provide superior flow distribution and reduced pressure drop compared to traditional plate designs in high-viscosity fluid applications.
5.2 Cold Water Distribution & Chilled Water Systems
- Chilled Water Loop Balancing: As discussed in the referenced thermal study, stainless steel coil tubes facilitate precise cold water balance by providing predictable, uniform heat absorption profiles — critical for maintaining set-point temperatures in multi-zone HVAC systems.
- Chiller Internal Components: Evaporator coils within centrifugal and screw chillers for water-to-refrigerant heat exchange.
- Cooling Tower Recirculation: Durable coil bundles for water-cooled condensers in industrial refrigeration.
5.3 Industrial & Process Applications
- Food & Beverage Processing: Pasteurization, sterilization, and cooling coils in sanitary-grade environments (FDA-compliant electropolished finish).
- Pharmaceutical Manufacturing: CIP (Clean-in-Place) compatible coils for bioreactor jacketing and heat recovery.
- Chemical Processing: Corrosion-resistant coil reactors and heat exchangers for aggressive chemical environments (316L grade).
- Power Generation: Feedwater heaters, condensers, and steam generators in thermal power plants.
5.4 Building Services
- Underfloor Radiant Heating/Cooling: Coil loops embedded in concrete slabs for hydronic radiant systems.
- District Heating Networks: High-pressure coil exchangers for heat recovery at substations.
6. Quality Certifications & Compliance
6.1 Standards & Certifications
| Certification / Standard | Scope | Relevance |
|---|---|---|
| ISO 9001:2015 | Quality Management System | Systematic quality assurance across all production stages |
| ISO 14001:2015 | Environmental Management System | Sustainable manufacturing practices |
| ISO/TS 22163 (IATF 16949 aligned) | Automotive Quality | For automotive A/C coil applications |
| EN 10204 Type 3.1 | Material Test Certificates | Third-party verified chemical & mechanical test reports |
| CE Marking (PED 2014/68/EU) | Pressure Equipment Directive | Compliance for pressure-vessel and heat exchanger integration |
| ASME / U Stamp | American National Standards | For North American pressure equipment applications |
| 3-A Sanitary Standard | Dairy & Food Equipment | Electropolished coil surfaces for food-grade compliance |
| NSF/ANSI 61 | Drinking Water Systems | Non-leaching certification for potable water contact |