Stainless Steel Coil Tube — HVAC Fan Coil Unit Heat Exchanger Coil

Product No.: 1133 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.

1. Product Overview

The Stainless Steel Coil Tube (盘管, Coiltube) is a precision-engineered heat exchange component designed primarily for use in HVAC (Heating, Ventilation, and Air Conditioning) fan coil units (FCUs). This product represents a critical subsystem in building climate control systems, where it facilitates efficient thermal energy transfer between circulating refrigerant or hot water and the ambient air stream. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this coil tube is engineered to meet the demanding operational requirements of commercial, industrial, and residential air conditioning systems.

The coil tube is delivered in a continuous coiled (盘管, coil) configuration, which enables compact installation within fan coil unit housings while maximizing the effective heat transfer surface area. The coiled geometry is optimized for laminar flow characteristics and minimal pressure drop across the heat exchange surface, contributing to overall system energy efficiency.

2. Material & Properties

The coil tube is fabricated from high-grade stainless steel, selected for its exceptional corrosion resistance, mechanical strength, and long-term thermal stability under repeated heating and cooling cycles.

2.1 Base Material Composition

• Grade Options: SUS304 (AISI 304), SUS316L (AISI 316L), and SUS321 (AISI 321), depending on application-specific corrosion and temperature requirements.
• Key Alloying Elements: Chromium (Cr) ≥ 18%, Nickel (Ni) ≥ 8% (for 304 grade); Molybdenum (Mo) ≥ 2% (for 316L grade) for enhanced chloride corrosion resistance.
• Maximum Carbon Content: ≤ 0.08% (standard grade); ≤ 0.03% (L-grade, low-carbon variant for welding applications).

2.2 Mechanical Properties

• Tensile Strength: ≥ 520 MPa (SUS304); ≥ 550 MPa (SUS316L)
• Yield Strength: ≥ 205 MPa
• Elongation: ≥ 40% (indicating excellent formability for coil winding processes)
• Hardness: ≤ 200 HB (annealed condition)

2.3 Thermal & Physical Properties

• Thermal Conductivity: 16.3 W/(m·K) at 20°C (SUS304); 14.6 W/(m·K) at 20°C (SUS316L)
• Operating Temperature Range: −196°C to +870°C (oxidation resistance up to 870°C in continuous air)
• Thermal Expansion Coefficient: 17.3 × 10⁻⁶ /°C (20–315°C)
• Density: 8.0 g/cm³ (SUS304); 8.03 g/cm³ (SUS316L)

2.4 Corrosion Resistance

• Excellent resistance to atmospheric corrosion, mild acids, and alkaline solutions
• SUS316L grade provides superior resistance to chloride-induced pitting and crevice corrosion, making it suitable for coastal and humid environments
• Resistance to stress corrosion cracking (SCC) at temperatures below 60°C in chloride environments

3. Technical Specifications

Parameter	Specification
Product Name	Stainless Steel Coil Tube (盘管, Coiltube)
Product Code	1133
Material Grade	SUS304 / SUS316L / SUS321 (selectable)
Outer Diameter (OD)	6.35 mm (1/4"), 9.52 mm (3/8"), 12.7 mm (1/2") — customizable
Wall Thickness	0.5 mm – 1.5 mm (standard); 0.3 mm – 2.0 mm (custom)
Coil Winding Diameter	25 mm – 150 mm (adjustable per FCU design)
Coil Height / Stack Height	100 mm – 600 mm (configurable)
Number of Rows	2, 4, 6, or 8 rows (standard configurations)
Tube Pitch (Lateral)	14.0 mm – 25.0 mm
Tube Pitch (Longitudinal)	16.0 mm – 30.0 mm
Fin Material	Aluminum (Al) or Stainless Steel (SUS304)
Fin Spacing	1.6 mm – 2.5 mm (FPI: 10–16 fins per inch)
Surface Treatment	Plain, Hydrophilic Coating, or Anti-Corrosion Coating
Connection Type	Flare, Flange, Solder, or Brazed connection
Maximum Operating Pressure	2.5 MPa (gas side); 1.6 MPa (liquid side)
Refrigerant Compatibility	R410A, R32, R22, R134a, R404A, R407C
Water Flow Rate (Hot Water)	0.5 – 5.0 L/min (depending on coil size)
Heat Transfer Capacity	2.0 – 25.0 kW (sensible + latent, depending on configuration)
Pressure Drop (Air Side)	≤ 150 Pa at rated air flow
Pressure Drop (Fluid Side)	≤ 50 kPa at rated flow rate
Delivery Form	Continuous coil (盘管, Coiltube) or pre-assembled heat exchanger unit
Customization	Available upon request — dimensions, material grade, and configuration

4. Manufacturing Process

The production of the stainless steel coil tube follows a rigorous, multi-stage manufacturing workflow designed to ensure dimensional accuracy, surface integrity, and mechanical reliability:

1. Raw Material Selection & Inspection:

   Stainless steel strip or seamless tube stock is procured from certified suppliers. Incoming material undergoes spectroscopic analysis (OES — Optical Emission Spectroscopy) to verify chemical composition compliance with the specified grade (e.g., ASTM A270 for stainless steel tubing).

2. Surface Cleaning & Degreasing:

   Raw material surfaces are cleaned using alkaline degreasing solutions followed by acid pickling to remove oxide scales and contaminants. This ensures optimal adhesion for subsequent coatings and prevents corrosion initiation sites.

3. Forming & Dimensional Shaping:

   For tube-based coils: seamless or welded stainless steel tubes are precision-cut to required lengths and deburred. For fin-and-tube configurations: aluminum or stainless steel fins are stamped from coil stock and slotted for tube insertion.

4. Coil Winding (盘管成型):

   The formed tubes are wound into the specified helical coil geometry using CNC-controlled winding machines. Winding parameters (pitch, diameter, tension) are precisely controlled to ensure uniform spacing and mechanical stability. The coiled configuration is critical for maximizing heat transfer surface area within a compact footprint.

5. Fin Attachment (if applicable):

   Fins are mechanically expanded or soldered onto the tubes to create the fin-and-tube heat exchanger structure. The bonding process ensures minimal thermal contact resistance between fins and tubes.

6. Hydrostatic Pressure Testing:

   Each coil assembly undergoes hydrostatic pressure testing at 1.5× the maximum rated operating pressure (typically up to 3.75 MPa) to verify structural integrity and detect any leaks or manufacturing defects.

7. Surface Coating Application:

   Hydrophilic or anti-corrosion coatings may be applied to the fin surfaces to enhance condensation performance and extend service life in aggressive environments. Coating thickness is controlled within ±10% tolerance.

8. Final Quality Inspection:

   Finished products undergo dimensional verification (using laser measurement systems), visual inspection, and performance testing (heat transfer coefficient measurement, pressure drop measurement) before packaging and dispatch.

5. Applications

The stainless steel coil tube is a versatile component with broad application across multiple industries:

5.1 HVAC Fan Coil Units (FCUs)

The primary application domain. The coil tube serves as the core heat exchange element in fan coil units used for:

• Commercial office buildings and retail spaces
• Hospital and healthcare facility air conditioning
• Hotel and hospitality industry climate control
• Residential central air conditioning systems

5.2 Energy Efficiency Optimization

As highlighted in the referenced study on fan coil unit control, operation regulation methods, and energy saving analysis, the coil tube design directly impacts the energy consumption profile of the entire HVAC system. Key energy-related considerations include:

• Variable Refrigerant Flow (VRF) system compatibility for demand-based capacity modulation
• Optimized coil geometry for reduced fan power consumption (lower air-side pressure drop)
• Hydrophilic fin coatings to improve latent heat transfer and reduce compressor cycling losses
• Enhanced thermal conductivity path to minimize temperature differential losses

5.3 Additional Application Domains

• Industrial Process Cooling: Heat recovery and cooling coils in manufacturing processes
• Food & Beverage Industry: Chiller coils and refrigeration heat exchangers (SUS316L grade for food-grade compliance)
• Pharmaceutical Facilities: Clean room HVAC systems requiring corrosion-resistant, easy-to-sanitize surfaces
• Marine & Offshore: HVAC systems in ships and offshore platforms (SUS316L for chloride resistance)
• Data Centers: Precision cooling systems for server room temperature control

6. Quality Certifications & Standards Compliance

Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management systems and product certifications to ensure international standards compliance:

6.1 Management System Certifications

• ISO 9001:2015 — Quality Management Systems
• ISO 14001:2015 — Environmental Management Systems
• ISO 45001:2018 — Occupational Health and Safety Management Systems

6.2 Product & Material Standards

• ASTM A269 / A270 — Standard specifications for austenitic stainless steel seamless, welded, and wrought austenitic stainless steel tubing
• ASTM A213 — Standard specification for seamless austenitic chromium-nickel stainless steel heat-exchanger and heat-treat exchanger tubing
• JIS G3446 — Japanese Industrial Standard for stainless steel tubing
• EN 10216-5 — European standard for seamless stainless steel tubes
• GB/T 14976 — Chinese national standard for seamless stainless steel tubes

6.3 Performance & Safety Certifications

• CE Marking — European Conformity for machinery and components
• UL Listed — Underwriters Laboratories safety certification (where applicable)
• CRAA Certification — China Refrigeration and Air Conditioning Industry Association product certification
• NSF/ANSI 61 — Drinking Water System Components (for food-grade applications)

6.4 Testing & Verification Protocols

• 100% hydrostatic pressure testing on all production units
• Random sampling for chemical composition verification (OES analysis)
• Dimensional inspection per AQL (Acceptable Quality Limit) sampling plans
• Heat transfer performance testing per AHRI (Air-Conditioning, Heating, and Refrigeration Institute) standards
• Corrosion resistance testing (salt spray test per ASTM B117, minimum 1000 hours for SUS316L)

7. Unique Selling Points

• Premium Material Grade: Full range of austenitic stainless steel grades (SUS304, SUS316L, SUS321) offering tailored corrosion resistance and mechanical properties for diverse operating environments.
• Precision Coiled Geometry: CNC-controlled winding ensures uniform tube spacing and optimal airflow distribution, directly contributing to energy efficiency and reduced fan power consumption.
• Energy-Saving Design: