Stainless Steel Coil Tube for Variable Fin-Spacing Evaporator Systems
Product Overview
The Stainless Steel Coil Tube (盘管, Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered heat exchange tubing solution designed for evaporator systems, particularly those employing three-row variable fin-spacing configurations. This product category encompasses seamless and welded stainless steel tubes formed into coil geometries that serve as the core heat transfer elements in refrigeration and air conditioning evaporators. The coil tube architecture enables optimized airflow distribution, enhanced heat transfer efficiency, and improved frosting performance characteristics in low-temperature and high-humidity operating environments.
Based on advanced research findings regarding the frosting behavior of three-row variable fin-spacing coil tube evaporators, Wenzhou Jixing Metal Materials has integrated empirical data and aerodynamic modeling into the design and manufacturing of their coil tube products, ensuring superior de-icing performance and extended operational cycles in refrigerated display cases, cold storage facilities, and industrial refrigeration systems.
Material & Properties
Primary Material Grades
- AISI 304 (UNS S30400): Austenitic stainless steel with 18% Chromium (Cr) and 8% Nickel (Ni). Excellent general corrosion resistance, weldability, and formability. Suitable for most refrigeration and food-grade applications.
- AISI 316 (UNS S31600): Austenitic stainless steel with 16-18% Cr, 10-14% Ni, and 2-3% Molybdenum (Mo). Superior resistance to chloride-induced pitting and crevice corrosion. Ideal for marine and chemical processing environments.
- AISI 316L (UNS S31603): Low-carbon variant of 316 with Carbon (C) content ≤ 0.03%. Enhanced weldability and resistance to sensitization during welding operations.
- AISI 321 (UNS S32100): Titanium (Ti)-stabilized austenitic stainless steel. Resistant to intergranular corrosion at elevated temperatures. Suitable for high-temperature evaporator applications.
- AISI 430 (UNS S43000): Ferritic stainless steel with 16-18% Cr. Cost-effective option with adequate corrosion resistance for indoor evaporator applications.
Mechanical Properties (Typical Values for AISI 304 Annealed Condition)
| Property | Symbol | Value | Unit |
|---|---|---|---|
| Tensile Strength (抗拉强度) | σb | ≥ 520 | MPa |
| Yield Strength (屈服强度) | σ0.2 | ≥ 205 | MPa |
| Elongation (延伸率) | A50 | ≥ 40 | % |
| Hardness (硬度) | — | ≤ 217 | HV |
| Thermal Conductivity (热导率, 25°C) | λ | 16.3 | W/(m·K) |
| Specific Heat Capacity (比热容, 25°C) | cp | 500 | J/(kg·K) |
| Coefficient of Thermal Expansion (热膨胀系数, 20-100°C) | α | 17.3 × 10-6 | 1/K |
Chemical Composition (AISI 304, wt%)
| Element | C | S | P | Cr | Ni | Mn | Si | N | Fe |
|---|---|---|---|---|---|---|---|---|---|
| Specification | ≤ 0.08 | ≤ 0.03 | ≤ 0.045 | 18.0-20.0 | 8.0-11.0 | ≤ 2.0 | ≤ 1.0 | ≤ 0.10 | Balance |
Specifications
Dimensional Parameters
| Parameter | Specification Range | Notes |
|---|---|---|
| Outer Diameter (外径, OD) | 6.0 mm – 12.7 mm (¼" – ½") | Standard refrigeration tube sizes |
| Wall Thickness (壁厚) | 0.3 mm – 1.0 mm | Customizable per application |
| Coil Bend Radius (盘管弯曲半径) | ≥ 3 × OD (minimum) | Ensures no wall thinning or wrinkling |
| Tube Length per Coil (单排管长) | 300 mm – 3000 mm | Configurable per evaporator design |
| Number of Rows (排数) | 1 – 5 rows (up to 7 for special orders) | Three-row configuration optimized for frosting resistance |
| Tube Pitch (管间距) | 10 mm – 25 mm | Variable pitch available for frosting optimization |
| Surface Treatment (表面处理) | Bright annealed (BA), Electropolished (EP), Passivated | EP surface reduces frost adhesion |
| Pressure Rating (耐压等级) | Up to 2.5 MPa (design pressure) | Hydrostatic test at 1.5 × design pressure |
| Operating Temperature Range (工作温度范围) | −196°C to +450°C | Full austenitic range for 304/316 grades |
| Standard References | ASTM A213, ASTM A269, GB/T 12771, EN 10216-5 | Multiplex standard compliance |
Variable Fin-Spacing Configuration (Three-Row Evaporator)
| Row Position | Fin Spacing (mm) | Design Rationale |
|---|---|---|
| Row 1 (Inlet/First Pass) | Wider spacing (e.g., 2.5–3.0 mm) | Reduces initial airflow resistance and frost formation at the leading edge |
| Row 2 (Middle Pass) | Medium spacing (e.g., 2.0–2.5 mm) | Balances heat transfer surface area with airflow penetration |
| Row 3 (Outlet/Last Pass) | Closer spacing (e.g., 1.5–2.0 mm) | Maximizes heat transfer where air is warmer and frost formation is minimal |
Manufacturing Process
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Raw Material Selection & Inspection (原材料筛选与检验):
Hot-rolled stainless steel strips or seamless pipe blanks are sourced from certified mills. Incoming material undergoes spectroscopic analysis (OES), chemical composition verification, and mechanical property testing per ASTM E1011 and ASTM A370 standards.
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Coil Forming & Cold Bending (盘管成型与冷弯):
Flat stainless steel strips are roll-formed into circular tube cross-sections using precision rotary draw bending machines. For seamless tube products, the bending process employs a minimum bend radius of 3×OD with internal and external mandrel support to prevent wall thinning (controlled ≤ 5% wall reduction at bend apex) and ovality distortion (≤ 2% of nominal OD).
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Welding Operations (焊接工序):
Where welded tube construction is specified, longitudinal or helical welds are performed via Automatic Submerged Arc Welding (SAW) or Gas Metal Arc Welding (GMAW). In-tube welding employs TIG (Tungsten Inert Gas) welding with Argon (Ar) shielding gas for both internal and external protection. Weld quality is verified per ASME Section IX qualification standards.
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Heat Treatment & Annealing (热处理与退火):
Post-forming annealing is conducted at 1050°C – 1100°C in a controlled atmosphere (Argon or Nitrogen) followed by rapid cooling. This restores full solution-annealed microstructure, eliminates cold-work hardening, and ensures maximum corrosion resistance. Solution annealing per ASTM A213/A269 specifications.
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Precision Dimensional Truing (精密定径):
Finished coil tubes pass through precision sizing rolls to achieve dimensional tolerances of ±0.05 mm on OD and ±10% on wall thickness per ASTM A269 tight tolerance specifications.
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Surface Finishing & Passivation (表面处理与钝化):
Electropolishing (EP) removes surface contaminants, reduces surface roughness to Ra ≤ 0.4 μm, and enhances the passive chromium oxide film. Chemical passivation with nitric acid (HNO3) or citric acid solution per ASTM A967 ensures formation of a stable, protective chromium oxide layer (Cr2O3) on the surface.
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Quality Inspection & Testing (质量检测与试验):
Non-Destructive Testing (NDT) includes dye penetrant testing (DPT) per ASTM E709, eddy current testing (ECT) per ASTM E309, and ultrasonic testing (UT) per ASTM E127. Hydrostatic pressure testing is performed at 1.5× design pressure for a minimum hold time of 30 seconds. Spectroscopic verification (PMI) confirms material grade compliance.
Applications
- Commercial Refrigeration (商用制冷): Refrigerated display cases, open-top merchandisers, and blast freezers where variable fin-spacing coil tube evaporators provide optimal frosting management and energy efficiency.
- Industrial Cold Storage (工业冷库): Plate-type evaporators and air-cooled evaporator units for warehouses, food processing plants, and pharmaceutical cold chain storage.
- Automotive Refrigeration (车用制冷): Refrigeration units for reefer trucks, maritime containers, and rail freight cooling systems operating in demanding environmental conditions.
- Food & Beverage Processing (食品饮料加工): Heat exchange systems requiring food-grade material compliance (FDA 21 CFR, EU 1935/2004) for pasteurization, chilling, and freezing applications.
- Pharmaceutical & Medical (医药医疗): Low-temperature storage for vaccines, biological samples, and pharmaceutical manufacturing processes requiring ultra-clean, corrosion-resistant heat exchange surfaces.
- Air Conditioning Systems (空调系统): Low-ambient temperature evaporator coils for commercial HVAC systems operating in cold climate regions.
Quality Certifications & Compliance
- ISO 9001:2015 — Quality Management System (质量管理体系认证)
- ISO 14001:2015 — Environmental Management System (环境管理体系认证)
- ISO 45001:2018 — Occupational Health & Safety Management System (职业健康安全管理体系认证)
- EN 10204 3.1 — Material Test Certificate (材质检验证书)
- EN 10204 3.2 — Inspection Report (第三方检验报告, where applicable)
- CE Marking — European Conformity for Pressure Equipment Directive (PED 2014/68/EU)
- ASME Stamp — National Board Registration for pressure vessel components (where applicable)
- NSF/ANSI 61 — Drinking Water System Components (for potable water applications)
- GB/T 12771 — Chinese National Standard for Seamless Stainless Steel Tubes for Fluid Transport
- GB/T 13296 — Chinese National Standard for Welded Stainless Steel Tubes for Fluid Transport
Unique Selling Points
Research-Driven Frosting Optimization: Wenzhou Jixing Metal Materials integrates peer-reviewed research findings on three-row variable fin-spacing coil tube evaporator frosting characteristics into product design, delivering coil tubes engineered for reduced frost accumulation, extended defrost cycles, and lower energy consumption compared to conventional uniform-spacing designs.
- Superior Frost Management: The variable tube pitch and optimized coil geometry reduce frost formation rate by up to 25–35% compared to uniform-spacing configurations, extending defrost intervals and improving system COP (Coefficient of Performance).
- Precision Manufacturing Tolerances: Cold-forming processes with computerized CNC bending ensure dimensional accuracy critical for fin-tube interface contact resistance, minimizing thermal contact resistance and maximizing heat transfer efficiency.
- Full Material Traceability: Every coil tube batch carries a unique heat number traceable to mill certificates, enabling complete supply chain transparency and regulatory compliance.
- Custom Engineering Capability: Custom coil configurations tailored to specific evaporator geometries, operating conditions, and frosting profiles, supported by CFD (Computational Fluid Dynamics) modeling and thermal performance simulation.
- Extended Service Life: Austenitic stainless steel construction with electropolished surfaces provides exceptional resistance to condensate corrosion, dehumidification cycle degradation, and long-term mechanical fatigue in continuous duty applications.
Technical Reference
This product specification is informed by the research study "Frosting Characteristics of Three-Row Variable Fin-Spacing Coil Tube Evaporator" (《三排变片距翅片盘管蒸发器结霜特性研究》), which provides empirical data on frost growth dynamics, airflow maldistribution patterns, and thermal performance degradation mechanisms in multi-row coil tube evaporator configurations. The findings directly inform the geometric optimization parameters specified in the dimensional specifications above.