Stainless Steel Coil Tube for Wall-Mounted Radiant Heating Systems
Product Overview
The stainless steel coil tube (盘管, Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product specifically designed for wall-mounted hot water radiant heating systems. This product category (Item No. 806) represents a specialized segment within the stainless steel tubing industry, where coiled tubing is embedded into wall structures to provide uniform, low-temperature radiant heat distribution. The coil tube serves as the core heat transfer medium in wall radiation systems, delivering thermal energy efficiently while maintaining structural integrity over extended service life.
Unlike conventional floor-embedded radiant systems, wall-mounted coil tube configurations offer superior thermal response times, reduced thermal inertia, and enhanced spatial flexibility. The coiled geometry maximizes heat exchange surface area within constrained wall cavities, making it an ideal solution for residential, commercial, and institutional heating applications.
Material & Properties
The coil tube is fabricated from austenitic stainless steel, predominantly utilizing grades that balance corrosion resistance, thermal conductivity, and formability. The primary material specifications are as follows:
- Base Material: Austenitic stainless steel (304 or 316 grade), offering excellent resistance to oxidation and scale formation at elevated operating temperatures
- Corrosion Resistance: Superior resistance to chloride-induced pitting corrosion, essential for long-term immersion in hot water circuits containing dissolved minerals
- Thermal Conductivity: Approximately 16.3 W/(m·K) for 304 grade, providing efficient heat transfer from the circulating medium to the wall surface
- Operating Temperature Range: Capable of sustained operation from ambient conditions up to 200°C without significant mechanical degradation
- Pressure Resistance: Designed to withstand operating pressures up to 1.0 MPa (10 bar) in closed-loop hydronic systems
- Creep Resistance: Maintains dimensional stability under prolonged thermal cycling conditions
Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 10 mm – 25 mm (customizable) | ASTM A269 / EN 10217 |
| Wall Thickness | 0.5 mm – 1.5 mm | — |
| Coil Diameter | 100 mm – 500 mm (configurable) | — |
| Coil Length per Spool | 50 m – 500 m | — |
| Surface Finish | No. 4 Brushed / Mirror Polish (Ra ≤ 0.4 μm) | ASTM A480 |
| End Condition | Cut to length, deburred, or threaded | — |
| Chemical Composition (304) | C ≤ 0.08%, Cr 18.0–20.0%, Ni 8.0–10.5% | ASTM A240 |
| Tensile Strength | ≥ 515 MPa | ASTM A269 |
| Yield Strength | ≥ 205 MPa | — |
| Maximum Operating Pressure | 1.0 MPa (10 bar) | EN 12828 |
| Design Service Life | ≥ 25 years | — |
| Delivery Form | Coiled (盘管) on spool or cut-to-length straight sections | — |
Manufacturing Process
The production of stainless steel coil tubes for radiant heating applications involves a multi-stage manufacturing sequence that ensures dimensional accuracy, mechanical performance, and surface quality:
- Slitting and Annealing: Cold-rolled stainless steel strip is slit to precise width and undergoes controlled annealing to relieve residual stresses and achieve desired grain structure for subsequent forming operations.
- Forming (Tube Milling): The flat strip is passed through a series of progressively reducing rollers in a tube mill to form the hollow tube cross-section. This cold-forming process ensures tight dimensional tolerances and consistent wall thickness.
- Seam Welding: The formed strip is joined using high-frequency induction welding (HFW) or orbital TIG welding to create a continuous, leak-tight seam. Weld quality is verified through non-destructive testing (NDT).
- Coiling: The continuous tube is wound into precise coil diameters using computer-controlled coiling equipment. The coiling process is carefully calibrated to avoid work hardening, kinking, or ovality introduction.
- Post-Coil Annealing (if required): Select grades undergo solution annealing followed by controlled cooling to restore full austenitic microstructure and eliminate any cold-work hardening induced during coiling.
- Precision Cutting and Finishing: Tubes are cut to specified lengths, deburred, and subjected to surface finishing (pickling and passivation) to remove any scale or contamination and enhance corrosion resistance.
- Quality Inspection: Each batch undergoes dimensional verification, hydrostatic pressure testing, and visual/ultrasonic inspection to confirm compliance with applicable standards.
Applications
The stainless steel coil tube is primarily engineered for the following applications:
- Wall-Mounted Radiant Heating Systems: The coil tube is embedded within wall structures (typically between structural wall and interior finish layer) to provide uniform surface radiation heating. Studies have demonstrated that the laying area of coil tubes directly influences thermal comfort parameters, including mean radiant temperature (MRT) and predicted mean vote (PMV) values.
- Partial Wall Coverage Heating: Localized coil tube installations can be strategically placed behind furniture walls, headboards, or partition walls to create targeted heating zones, optimizing energy consumption in occupied spaces.
- Hydronic Floor Heating (Alternative Configuration): In straightened form, the same tube can be deployed in floor-embedded radiant heating systems where stainless steel's corrosion resistance provides a significant advantage over conventional polymer piping.
- Industrial Process Heating: High-temperature coil tube configurations serve as heat exchangers in industrial processes requiring corrosion-resistant tubular heat transfer surfaces.
- Refrigeration and HVAC Systems: The excellent thermal conductivity and formability of the coil tube make it suitable for condenser and evaporator coil applications in air conditioning systems.
Unique Selling Points
- Exceptional Longevity: Austenitic stainless steel construction ensures a service life exceeding 25 years without degradation, significantly outperforming copper and polymer alternatives in closed-loop hydronic systems.
- Superior Corrosion Resistance: Immunity to galvanic corrosion when in contact with dissimilar metals, eliminating a common failure mode in mixed-material heating installations.
- Compact Coil Geometry: The pre-coiled configuration reduces on-site installation time and labor costs by minimizing the need for on-site bending and forming operations.
- Thermal Performance Optimization: The coiled arrangement within wall cavities provides a higher heat transfer surface area per unit of wall volume compared to straight-tube configurations, enabling more efficient thermal distribution with smaller pipe diameters.
- Hygienic Surface Quality: Mirror-polished or passivated inner surfaces prevent biofilm accumulation and scale deposition, maintaining consistent flow characteristics and heat transfer efficiency over the system's operational life.
- Environmental Sustainability: Stainless steel is 100% recyclable, contributing to reduced lifecycle environmental impact compared to single-use polymer alternatives.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality management systems and ensures all stainless steel coil tube products comply with the following international standards and certifications:
- ISO 9001:2015 — Quality Management System certification for consistent product quality and process control
- ISO 14001:2015 — Environmental Management System certification for sustainable manufacturing practices
- EN 10217-7 — Seamless and welded stainless steel tubes for pressure purposes
- ASTM A269/A269M — Welded austenitic stainless steel tube for chemical and similar severe service applications
- EN 12828 — Heating systems in buildings, component requirements and performance
- GB/T 12771 — Chinese national standard for welded stainless steel tubes for general application
- Mill Test Certificates (MTC): Provided for each batch, documenting chemical composition, mechanical properties, and heat treatment history in accordance with EN 10204 Type 3.1
- Pressure Testing: All production lots undergo hydrostatic pressure testing at 1.5× the maximum design pressure with zero leakage tolerance
Technical Note: Research published regarding wall-mounted hot water coil tube radiant systems has demonstrated that the thermal comfort performance of these systems is significantly influenced by the coil tube laying area relative to the total wall surface. Optimal configurations typically achieve coil coverage ratios between 60–80% of the heated wall area, balancing thermal output, installation cost, and occupant comfort metrics (PMV/PPD). This product line is engineered to accommodate various coverage ratios, providing designers with flexibility in system optimization.