Stainless Steel Coil Tube (Coiltube) for Shell-and-Coil Heat Exchanger GSN
Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered tubular component specifically designed for integration into the Shell-and-Coil Heat Exchanger (GSN) system, a novel architecture employed in modern air-cooled heat pump (Air-Cooled Heat Pump, AC-HP) units. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this coil tube serves as the core heat transfer element within the shell-and-coil configuration, facilitating efficient thermal exchange between the refrigerant circuit and the ambient air stream.
The GSN heat exchanger represents an innovative departure from conventional fin-and-tube and shell-and-tube designs, combining the compact geometry of a coil arrangement within a protective shell envelope. This architecture offers superior surface-area-to-volume ratios, reduced pressure drop across the coil passages, and enhanced resistance to fouling and icing—critical advantages in air-cooled heat pump applications operating across a wide range of ambient conditions.
Material & Properties
The coil tube is fabricated from high-purity austenitic stainless steel, selected for its outstanding corrosion resistance, thermal conductivity, mechanical integrity, and long-term serviceability in demanding HVAC (Heating, Ventilation, and Air Conditioning) environments.
- Base Material: Stainless Steel (SS) Grade 304 (UNS S30408) or Grade 316 (UNS S31603), depending on application-specific corrosion requirements
- Chromium (Cr) Content: 18–20% (Grade 304) / 16–18% (Grade 316)
- Nickel (Ni) Content: 8–10.5% (Grade 304) / 10–14% (Grade 316)
- Molybdenum (Mo) Content: ≤0.08% (Grade 304) / 2–3% (Grade 316)
- Carbon (C) Maximum: 0.08%
- Thermal Conductivity: 16.3 W/(m·K) at 100°C (Grade 304); 14.6 W/(m·K) at 100°C (Grade 316)
- Tensile Strength: ≥515 MPa (Grade 304); ≥515 MPa (Grade 316)
- Yield Strength: ≥205 MPa
- Elongation at Break: ≥40%
- Operating Temperature Range: −196°C to +870°C (Grade 304); −196°C to +870°C (Grade 316)
- Surface Finish: Mill finish or electropolished (Ra ≤ 0.4 μm) for reduced fouling resistance
Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) |
| Item No. | 572 |
| Designation | GSN Shell-and-Coil Heat Exchanger Component |
| Tube Outer Diameter (OD) | 6.0 mm / 7.94 mm / 8.0 mm / 9.53 mm (available options) |
| Tube Wall Thickness | 0.3 mm – 0.8 mm (customizable per design requirement) |
| Coil Mean Diameter (CMD) | 50 mm – 300 mm (application-dependent) |
| Coil Pitch | 8 mm – 15 mm (adjustable for thermal performance optimization) |
| Number of Turns | 10 – 120 turns (customizable) |
| Tube Length (Uncoiled) | 3 m – 25 m |
| Material Grade | SS 304 / SS 316 / SS 316L (Low Carbon) |
| End Connection Type | Straight ends / Flared ends / Threaded fittings / Brazed ends |
| Pressure Rating | Up to 4.0 MPa (40 bar) at 25°C |
| Refrigerant Compatibility | R410A, R32, R134a, R404A, R407C, R290 (Propane) |
| Compliance Standards | ASTM A269, ASTM A312, EN 10216-5, GB/T 12771 |
Manufacturing Process
The production of the GSN coil tube follows a rigorously controlled manufacturing sequence to ensure dimensional accuracy, metallurgical integrity, and consistent thermal performance:
- Raw Material Selection & Inspection: Cold-rolled stainless steel strip is sourced from certified mill producers and subjected to spectroscopic analysis (Optical Emission Spectrometry, OES) to verify chemical composition within ASTM/EN specification limits.
- Tube Forming (Cold Drawing): The strip is cold-formed into a seamless circular tube using high-precision rotary draw bending (Rotary Draw Bending, RDB) or orbital forming equipment, ensuring uniform wall thickness and minimal residual stress.
- Coil Winding: The formed tube is wound into the specified coil geometry using CNC-controlled coil winding machinery. The winding process maintains constant pitch, avoids kinking or flattening, and produces a helical coil with tight dimensional tolerances (±0.5 mm on CMD, ±0.3 mm on pitch).
- Stress Relief Annealing: The coiled tube undergoes controlled stress relief annealing at 350–450°C under inert atmosphere (Nitrogen, N₂) to eliminate cold-work-induced residual stresses while preserving the desired mechanical properties and preventing sensitization.
- Surface Treatment: Optional electropolishing or passivation treatment is applied to remove surface contaminants, enhance chromium oxide layer formation, and improve long-term corrosion resistance and antifouling characteristics.
- End Processing: Tube ends are trimmed, deburred, and prepared for the specified connection type (brazing, threading, flaring, or welding) using automated end-finishing stations.
- Quality Inspection: Each coil tube undergoes non-destructive testing (NDT), including dye penetrant inspection (DPI) for surface defects, hydrostatic pressure testing at 1.5× working pressure, and dimensional verification via coordinate measurement machine (Coordinate Measuring Machine, CMM).
- Packaging & Dispatch: Inspected coils are packaged in protective packaging with moisture-absorbing desiccants to prevent intergranular corrosion during storage and transportation.
Applications
The Stainless Steel Coil Tube for GSN heat exchangers is engineered for deployment in the following application domains:
- Air-Cooled Heat Pumps (AC-HP): Primary application—serving as the condenser or evaporator coil within the shell-and-coil heat exchanger, enabling high-efficiency heat transfer between refrigerant and ambient air in commercial and industrial heat pump systems.
- Commercial HVAC Systems: Rooftop units, packaged terminal units, and central air handling units requiring compact, high-performance heat exchanger components.
- Industrial Process Heating & Cooling: Applications requiring corrosion-resistant heat transfer in chemical processing, food and beverage production, and pharmaceutical manufacturing.
- Marine & Offshore Systems: Where chloride-induced corrosion resistance is paramount, SS 316/316L grade coil tubes provide reliable performance in saltwater-laden environments.
- Low-Temperature Refrigeration: Freezer and cold storage systems operating at sub-zero temperatures where austenitic stainless steel retains full ductility and toughness.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring that every coil tube product meets international standards and regulatory requirements:
- ISO 9001:2015 — Quality Management System certification for consistent manufacturing quality
- ISO 14001:2015 — Environmental Management System certification for sustainable production practices
- EN 10204 3.1 — Material Certification (Third-party verified test reports)
- ASTM A269 / A312 — Conformity with American Society for Testing and Materials (ASTM) specifications for austenitic stainless steel tubing
- GB/T 12771 — Compliance with Chinese National Standard for stainless steel seamless tubes
- CE Marking — Conformity with European Union directives for market access
- RoHS Compliance — Restriction of Hazardous Substances directive adherence
Unique Selling Points
The GSN Shell-and-Coil Heat Exchanger coil tube from Wenzhou Jixing Metal Materials Co., Ltd. distinguishes itself through several key technical advantages:
1. Superior Thermal Performance: The helical coil geometry maximizes heat transfer surface area within a compact shell envelope, achieving thermal efficiency gains of 15–25% compared to conventional straight-tube shell-and-tube designs.
2. Enhanced Anti-Icing & Anti-Fouling Characteristics: The continuous helical surface promotes self-draining of condensate and reduces ice adhesion, significantly extending service intervals in air-cooled applications.
3. Low Pressure Drop: The smooth, continuous coil path minimizes flow resistance and turbulence-induced pressure losses, reducing compressor power consumption and improving system Coefficient of Performance (COP).
4. Full Stainless Steel Construction: Eliminates galvanic corrosion risks inherent in copper-aluminum hybrid designs, ensuring service life exceeding 20 years without degradation.
5. Customizable Geometry: Flexible manufacturing capability allows coil mean diameter, pitch, number of turns, and tube dimensions to be tailored to specific thermal load requirements and spatial constraints.
6. Environmentally Friendly Refrigerant Compatibility: Certified for use with next-generation low Global Warming Potential (GWP) refrigerants including R290 and R1234ze, supporting compliance with evolving environmental regulations.
Technical Reference
This product specification is informed by the technical study and application analysis documented in "Novel Shell-and-Coil Heat Exchanger GSN for Air-Cooled Heat Pumps", reflecting industry-leading research into advanced heat exchanger architectures for high-efficiency thermal management systems.