Stainless Steel Coil Tube for Double-Layer Floor Heating Systems
Product Overview
The Stainless Steel Coil Tube (盘管, Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered product specifically designed for double-layer floor radiant heating systems (Double-Layer Floor Heating System). Based on extensive numerical simulation and optimization analysis of thermal-fluid dynamics within multi-layer coil configurations, this product delivers superior heat transfer efficiency, uniform temperature distribution, and long-term structural integrity under cyclic thermal loading conditions.
Unlike conventional single-layer coil floor heating installations, the double-layer coil tube system enables enhanced thermal output density while maintaining manageable hydraulic resistance. The coil tube geometry is optimized to minimize flow maldistribution and maximize convective heat exchange between the working fluid and the floor slab, as validated through computational fluid dynamics (CFD) and finite element analysis (FEA).
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional combination of corrosion resistance, thermal conductivity, mechanical strength, and weldability. The primary material grades offered include:
- 304 (AISI 304 / UNS S30408) — General-purpose austenitic stainless steel with excellent corrosion resistance in non-chloride environments. Composition: ≥18% Cr, ≥8% Ni, ≤0.08% C.
- 316L (AISI 316L / UNS S31603) — Low-carbon, molybdenum-bearing austenitic stainless steel offering superior resistance to pitting and crevice corrosion in chloride-containing media. Composition: ≥16.5% Cr, ≥10% Ni, ≥2% Mo, ≤0.03% C.
- 321 (AISI 321 / UNS S32100) — Titanium-stabilized austenitic stainless steel providing enhanced resistance to intergranular corrosion at elevated temperatures. Composition: ≥17% Cr, ≥9% Ni, 0.5–0.8% Ti.
Key material properties of the base steel (304 grade, annealed condition):
- Tensile Strength (抗拉强度): ≥515 MPa
- Yield Strength (屈服强度): ≥205 MPa
- Elongation (延伸率): ≥40%
- Thermal Conductivity (热导率): 16.3 W/(m·K) at 20°C
- Thermal Expansion Coefficient (热膨胀系数): 17.3 × 10⁻⁶ /°C
- Maximum Operating Temperature (最高使用温度): 870°C (oxidizing atmosphere)
Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Outer Diameter (OD, 外径) | 10 mm, 12 mm, 14 mm, 16 mm, 20 mm | ASTM A269 / EN 10216-5 |
| Wall Thickness (壁厚) | 0.8 mm, 1.0 mm, 1.2 mm, 1.5 mm, 2.0 mm | ASTM A269 / EN 10216-5 |
| Coil Pitch (盘管间距) | 50 mm, 80 mm, 100 mm, 120 mm, 150 mm | ISO 12645 |
| Coil Diameter (盘管直径) | 50 mm – 300 mm (customizable) | Enterprise Standard (Q/JX) |
| Tube Length per Coil (单圈管长) | 5 m – 100 m (configurable) | Enterprise Standard (Q/JX) |
| Surface Finish (表面光洁度) | Mirror polished (Ra ≤ 0.2 μm) or Pickle & Passivate (Ra ≤ 0.8 μm) | ASTM A240 |
| Operating Pressure (工作压力) | ≤ 1.0 MPa (standard); ≤ 1.6 MPa (reinforced) | EN 12828 |
| Operating Temperature Range (工作温度范围) | -30°C to +95°C | EN 12828 / ASHRAE 90.1 |
| Layer Configuration (层数配置) | Double-layer (双层) — Upper layer + Lower layer | Enterprise Standard (Q/JX) |
| Hydraulic Connection (液压接口) | Compression fittings, threaded adapters (G1/2", G3/4", G1") | EN 1254 / DIN 2353 |
| Maximum Flow Velocity (最大流速) | ≤ 2.5 m/s (recommended ≤ 1.5 m/s) | ASHRAE Guideline 3 |
| Service Life (设计寿命) | ≥ 50 years (under design conditions) | EN 12828 |
Manufacturing Process
The production of the stainless steel coil tube follows a rigorous, multi-stage manufacturing workflow designed to ensure dimensional accuracy, metallurgical integrity, and hydraulic performance:
- Raw Material Inspection (原材料检验) — Incoming stainless steel strip or tube stock is verified for chemical composition (via spark OES and wet chemistry), mechanical properties, and surface quality in accordance with ASTM E415 and ASTM E8.
- Forming & Bending (成型与弯曲) — Precision CNC tube bending equipment forms the straight tube into the specified coil geometry. Bend radii are controlled to prevent wall thinning (thinning ratio ≤ 8%) and ovality (ovality ≤ 3% of OD). The double-layer configuration is achieved through sequential bending and layering with controlled inter-layer spacing.
- Welding (焊接) — Where continuous tube lengths require joining, orbital TIG welding (Gas Tungsten Arc Welding, GTAW) is employed per ASTM A213 and ISO 6844. Weld procedures are qualified per ASME Section IX. Back-purging with argon gas ensures a clean, oxide-free weld interior.
- Pickle & Passivation (酸洗钝化) — The finished coil tube undergoes chemical pickling (HNO₃/HF blend) and passivation treatment to remove welding oxides and establish a protective chromium oxide layer. Passivation effectiveness is verified via ferric ion spot test (ASTM A380).
- Hydrostatic Pressure Testing (水压试验) — Each coil assembly is pressure-tested at 1.5× the maximum operating pressure for a minimum of 15 minutes to verify leak-tightness and structural integrity.
- Final Dimensional & Visual Inspection (最终尺寸与目视检验) — Coil pitch, tube OD, wall thickness, and surface finish are measured and documented. All units receive a unique traceability identification number.
Applications
The double-layer stainless steel coil tube system is engineered for high-performance radiant floor heating applications where thermal efficiency, space utilization, and durability are critical:
- Residential Floor Heating (住宅地板采暖) — Whole-home and room-level hydronic floor heating with dual-layer coil architecture providing enhanced heat flux density in compact floor areas.
- Commercial & Institutional Buildings (商业与公共建筑) — Large-scale installations in hotels, hospitals, office buildings, and educational facilities requiring uniform temperature control and energy efficiency.
- Industrial Process Heating (工业过程加热) — Floor-mounted heating in manufacturing facilities, greenhouses, and cold storage transition zones where corrosion resistance is paramount.
- Snow Melt Systems (融雪系统) — Coil tube embedded in driveways, walkways, and parking structures for passive and active de-icing.
- Underfloor Radiant Cooling (地板辐射冷却) — High-temperature differential (HTD) cooling systems utilizing the thermal mass of the coil slab for latent heat management.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management and product certification programs to ensure international market readiness:
- ISO 9001:2015 — Quality Management Systems (质量管理体系)
- ISO 14001:2015 — Environmental Management Systems (环境管理体系)
- ISO 45001:2018 — Occupational Health & Safety Management Systems (职业健康安全管理体系)
- EN 10204 3.1 — Material Test Reports (材料试验报告) provided with each shipment
- CE Marking — Conformity with European Construction Products Regulation (CPR), EN 12828 for floor heating systems
- SGS / TÜV / BV — Third-party inspection and verification available upon request
- Mill Test Certification — Full chemical and mechanical analysis certificates for all material grades
Unique Selling Points
1. Numerically Optimized Double-Layer Architecture (数值优化双层结构)
The coil tube geometry is derived from rigorous numerical simulation of conjugate heat transfer and fluid flow in double-layer floor systems. This optimization minimizes hydraulic imbalance between layers, ensures uniform heat flux distribution across the floor surface, and reduces the total tube length required compared to single-layer equivalents — resulting in lower installation cost and reduced pumping energy consumption.2. Superior Corrosion & Fatigue Resistance (优异的耐腐蚀与抗疲劳性能)
Austenitic stainless steel construction provides immunity to galvanic corrosion in mixed-material piping systems and resistance to thermal fatigue under repeated heating/cooling cycles. This ensures a design service life exceeding 50 years without degradation of hydraulic or thermal performance.3. Precision Manufacturing & Traceability (精密制造与全程追溯)
CNC-controlled bending, orbital welding, and multi-stage inspection ensure consistent dimensional accuracy. Each product unit carries a unique traceability identifier linked to raw material mill certificates, weld logs, and pressure test records — enabling full lifecycle quality accountability.4. Modular & Customizable Design (模块化与定制化设计)
Coil pitch, tube diameter, wall thickness, layer spacing, and connection configurations are customizable to match specific project requirements, floor construction types, and heat load calculations. Standard modular units facilitate rapid on-site installation with minimal waste.5. Energy Efficiency Contribution (节能贡献)
The optimized coil tube system operates at lower supply water temperatures (35°C – 50°C) compared to conventional radiator systems, enabling seamless integration with high-efficiency heat pumps, solar thermal collectors, and district heating networks — reducing primary energy consumption by 20–35%.