Stainless Steel Coil Tube (盘管 / Coil Tube) — HVAC & Thermal Transfer Applications
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
Product Series No.: 519
Classification: Industrial Literature & Technical Reference
1. Product Overview
The Stainless Steel Coil Tube (盘管) is a precision-engineered tubular component manufactured by Wenzhou Jixing Metal Materials Co., Ltd., designed for high-efficiency thermal transfer applications, particularly within HVAC (Heating, Ventilation, and Air Conditioning) systems. This product is specifically optimized for use in Fan Coil Units (FCUs), including advanced configurations such as series-connected fan coil terminals operating under large temperature differential (LTD) conditions.
Coil tubes serve as the critical heat exchange medium in air conditioning end-terminal systems. In conventional HVAC architectures, coil tubes are arranged in serpentine or helical configurations within the evaporator and condenser sections of fan coil units. The product described herein is engineered to address the thermal management challenges inherent in large temperature differential systems, where supply air temperatures deviate significantly from ambient conditions, demanding superior thermal conductivity, structural integrity, and corrosion resistance.
Based on the research framework outlined in the study "Research on Large Temperature Differential Air Conditioning Terminals Based on Series-Connected Fan Coil Units", this coil tube product represents a technological advancement in the field of thermal end-terminal systems, enabling more efficient energy distribution and superior indoor climate control.
2. Material & Properties
The coil tube is fabricated from premium-grade stainless steel, selected for its exceptional combination of mechanical strength, thermal performance, and long-term durability in demanding environmental conditions.
2.1 Primary Material Grades
- SUS304 (AISI 304 / UNS S30408): The standard-grade austenitic stainless steel offering excellent general corrosion resistance, formability, and weldability. Suitable for most HVAC applications.
- SUS316L (AISI 316L / UNS S31603): Low-carbon austenitic stainless steel with added molybdenum (Mo) content, providing enhanced resistance to pitting and crevice corrosion. Recommended for coastal, marine, or chemically aggressive environments.
- SUS321 (AISI 321 / UNS S32100): Titanium-stabilized austenitic stainless steel offering superior resistance to intergranular corrosion at elevated temperatures, suitable for high-temperature differential applications.
2.2 Key Material Properties
| Property | SUS304 | SUS316L | SUS321 |
|---|---|---|---|
| Chemical Composition (Cr) | 18.0–20.0% | 16.0–18.0% | 17.0–19.0% |
| Chemical Composition (Ni) | 8.0–10.5% | 10.0–14.0% | 9.0–12.0% |
| Chemical Composition (Mo) | — | 2.0–3.0% | — |
| Tensile Strength (MPa) | ≥520 | ≥485 | ≥515 |
| Yield Strength (MPa) | ≥205 | ≥170 | ≥205 |
| Elongation (%) | ≥40 | ≥40 | ≥40 |
| Thermal Conductivity (W/m·K) | 16.3 | 14.6 | 16.3 |
| Maximum Service Temperature (°C) | 870 | 870 | 900 |
| Density (g/cm³) | 8.00 | 8.00 | 8.00 |
2.3 Surface Finish Options
- 2B Finish: Cold-rolled, annealed, and pickled surface with a moderate luster; standard industrial finish.
- No.4 Brushed Finish: Uniform linear grain pattern providing enhanced aesthetic appearance and scratch resistance.
- Mirror (8K) Finish: High-polish reflective surface for premium applications requiring maximum visual quality.
- Pickled & Passivated: Chemically cleaned surface with a protective chromium oxide passive layer for maximum corrosion resistance.
3. Technical Specifications
| Parameter | Specification |
|---|---|
| Product Type | Stainless Steel Coil Tube (盘管 / Coil Tube) |
| Product Series No. | 519 |
| Outer Diameter (OD) | 6.0 mm / 8.0 mm / 9.52 mm / 12.0 mm / 15.88 mm / Custom |
| Wall Thickness | 0.5 mm – 2.0 mm (Customizable) |
| Tube Length (Straight Section) | Up to 6,000 mm per coil |
| Coil Inner Diameter (ID) | 200 mm – 600 mm (Configurable) |
| Coil Height | 50 mm – 200 mm |
| Number of Rows | 2 – 8 rows (Series-Connected Configuration Available) |
| Pitch (Horizontal) | 12 mm – 25 mm |
| Pitch (Vertical) | 15 mm – 30 mm |
| Bend Radius | ≥ 3× OD (Minimum Bend Radius) |
| Operating Pressure | Up to 1.6 MPa (Standard); Up to 4.0 MPa (Reinforced) |
| Operating Temperature Range | −40°C to +250°C |
| Heat Transfer Medium | Water, Glycol-Water Mixture, Refrigerant (R-410A, R-32, R-134a) |
| End Treatment | Flanged, Threaded (BSP/NPT), Grooved, or Plain |
| Welding Method | TIG (Tungsten Inert Gas) / Argon Arc Welding |
| Manufacturing Standard | GB/T 14976, ASTM A269, EN 10216-5 |
| Customization | Available upon request (OD, Wall Thickness, Configuration, Finish) |
3.1 Dimensional Tolerances
- OD Tolerance: ±0.05 mm (Precision Grade); ±0.10 mm (Standard Grade)
- Wall Thickness Tolerance: ±0.03 mm (Precision Grade); ±0.05 mm (Standard Grade)
- Coil Roundness: ≤ 0.5% of nominal ID
- Straightness of Tangent Sections: ≤ 1.0 mm/m
4. Manufacturing Process
The production of Wenzhou Jixing's stainless steel coil tubes follows a rigorous, multi-stage manufacturing workflow designed to ensure dimensional accuracy, structural integrity, and superior surface quality.
4.1 Process Flow
- Raw Material Inspection: Incoming stainless steel tubing is subjected to spectroscopic analysis (OES), chemical composition verification, and mechanical property testing to confirm compliance with specified grades (SUS304, SUS316L, or SUS321).
- Cutting & Preparation: Tubes are precision-cut to required lengths using CNC-controlled cold-cut saws, ensuring square ends within ±0.1 mm tolerance.
- Forming & Bending: Tubes are formed into serpentine or helical coil configurations using CNC-controlled rotary draw bending machines. The minimum bend radius is maintained at ≥ 3× OD to prevent wall thinning, ovalization, or wrinkling.
- Welding (TIG/Argon Arc): Header connections and inter-row transitions are joined using Tungsten Inert Gas (TIG) welding under shielding gas (Argon, 99.99% purity). Weld parameters are precisely controlled to minimize heat-affected zone (HAZ) distortion and ensure full penetration.
- Heat Treatment (if applicable): For specific grades or applications, solution annealing (1010–1150°C) followed by rapid quenching is performed to restore full austenitic microstructure and maximize corrosion resistance.
- Pickling & Passivation: Welded assemblies undergo acid pickling (HNO₃/HF solution) to remove oxide scale, followed by passivation treatment to establish a uniform chromium oxide protective layer on the surface.
- Surface Finishing: Tubes receive the specified surface finish (2B, No.4 Brushed, or 8K Mirror) through mechanical polishing, chemical etching, or electropolishing processes.
- Pressure Testing: Each coil tube assembly is hydrostatically tested at 1.5× the maximum operating pressure (minimum 2.4 MPa) for a sustained period of ≥ 30 minutes to verify leak-tightness and structural soundness.
- Final Inspection & Quality Control: Comprehensive dimensional verification, visual inspection, and non-destructive testing (NDT) including dye penetrant testing (PT) or magnetic particle inspection (MT) are performed on critical weld joints and tube sections.
- Packaging & Dispatch: Finished coil tubes are packaged with protective end caps, anti-corrosion wrapping, and wooden crate or pallet securing for safe transportation.
5. Applications
The Wenzhou Jixing Stainless Steel Coil Tube (Series 519) is engineered for a broad spectrum of industrial and commercial applications, with particular emphasis on advanced HVAC thermal terminal systems.
5.1 Primary Applications
- Large Temperature Differential (LTD) Air Conditioning Systems: Specifically designed for series-connected fan coil unit (FCU) configurations where supply air temperatures range from −10°C to +40°C, enabling significant energy savings through reduced pumping power and enhanced system efficiency.
- Commercial & Industrial HVAC Systems: Evaporator and condenser coil tubes for chiller units, air handlers, rooftop units, and centralized air conditioning systems in commercial buildings, hospitals, and industrial facilities.
- Process Cooling & Heating: Heat exchanger coil tubes for chemical processing, food and beverage production, pharmaceutical manufacturing, and semiconductor fabrication facilities.
- Refrigeration Systems: Evaporator and condenser coils for commercial refrigeration units, cold storage facilities, and cryogenic applications.
- Geothermal & Renewable Energy Systems: Coil tubes for ground-source heat pump systems and solar thermal collectors.
5.2 Series-Connected Fan Coil Unit Configuration
In the series-connected fan coil architecture referenced in the research literature, multiple coil tube units are arranged in a cascading (series) configuration. This design allows for staged thermal output, where each coil tube stage progressively adjusts the air temperature. The stainless steel coil tubes in this configuration must withstand repeated thermal cycling and maintain consistent heat transfer performance across varying operating loads. Wenzhou Jixing's coil tubes are specifically optimized for this demanding application through enhanced thermal fatigue resistance and uniform wall thickness throughout the coil geometry.
5.3 Industry Sectors
- Commercial Real Estate & Building Services
- Healthcare Facilities (Hospitals, Laboratories)
- Food Processing & Dairy Industry
- Pharmaceutical Manufacturing
- Electronics & Semiconductor Cleanrooms
- Marine & Offshore Platforms
- Power Generation & Energy Systems
6. Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework to ensure that every coil tube product meets or exceeds international standards and customer requirements.
6.1 Management System Certifications
- ISO 9001: