Stainless Steel Coil Tube — Calorimeter-Grade Refrigerant Flow Application (Product No. 252)
1. Product Overview
The Stainless Steel Coil Tube (盘管 / Coil Tube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product designed for demanding thermal-fluid applications, particularly in calorimetric measurement systems, refrigerant circulation loops, and heat exchanger assemblies. This product is specifically optimized for the flow characteristics of R-134a (1,1,1,2-Tetrafluoroethane) refrigerant within calorimeter coil configurations, as validated through rigorous experimental analysis and structural optimization studies.
Coil tubes represent a critical component in thermodynamic research and industrial heat transfer systems. The geometry of a coil tube — characterized by its helical winding, uniform curvature, and consistent cross-section — directly influences the hydraulic resistance, heat transfer efficiency, and pressure drop behavior of the fluid traversing it. The product offered here embodies advanced metallurgical design principles to ensure superior flow stability, thermal conductivity, and long-term mechanical integrity under cyclic thermal loading conditions.
Technical Reference: The structural design and performance parameters of this coil tube are informed by the research paper "Analysis of Flow Characteristics of R-134a in Calorimeter Coil Tubes and Structural Optimization of Coil Tubes", which provides a comprehensive framework for optimizing coil geometry to minimize flow maldistribution and maximize heat exchange efficiency in refrigerant-based calorimetric systems.
2. Material & Properties
2.1 Base Material Composition
The coil tube is fabricated from AISI 304 or AISI 316L austenitic stainless steel (奥氏体不锈钢), selected for their exceptional corrosion resistance, thermal stability, and non-magnetic properties essential for precise calorimetric measurements.
- AISI 304 (UNS S30400): Contains 18–20% Chromium (Cr) and 8–10.5% Nickel (Ni), offering excellent general corrosion resistance and weldability. Suitable for non-chloride environments.
- AISI 316L (UNS S31603): Enhanced with 2–3% Molybdenum (Mo) and reduced carbon content (<0.03%), providing superior resistance to pitting corrosion, crevice corrosion, and stress corrosion cracking (SCC) in aggressive or chloride-containing environments.
2.2 Key Mechanical & Thermal Properties
| Property | AISI 304 | AISI 316L | Unit |
|---|---|---|---|
| Tensile Strength (抗拉强度) | ≥ 515 | ≥ 485 | MPa |
| Yield Strength (屈服强度, 0.2% Offset) | ≥ 205 | ≥ 170 | MPa |
| Elongation (延伸率) | ≥ 40 | ≥ 40 | % |
| Thermal Conductivity (导热系数, 20°C) | 16.3 | 14.6 | W/(m·K) |
| Specific Heat Capacity (比热容, 20°C) | 500 | 500 | J/(kg·K) |
| Thermal Expansion Coefficient (热膨胀系数, 20–100°C) | 17.3 | 16.0 | ×10⁻⁶ /K |
| Density (密度) | 8.00 | 8.03 | g/cm³ |
| Operating Temperature Range (工作温度范围) | −196 to +870 | −196 to +870 | °C |
2.3 Surface Finish
The interior surface of the coil tube is machined to a RA (Roughness Average) ≤ 0.4 μm finish, ensuring minimal frictional losses and preventing nucleation sites that could disrupt laminar-to-turbulent flow transitions critical for accurate calorimetric measurements. The exterior surface may be supplied in a 2B finish (bright annealed) or No. 4 brushed finish, depending on the application requirement.
3. Specifications
| Parameter | Specification |
|---|---|
| Product Name (产品名称) | Coil Tube (盘管) |
| Product No. (序号) | 252 |
| Material Grade (材质) | AISI 304 / AISI 316L |
| Outer Diameter (OD, 外径) | 6 mm – 38 mm (customizable) |
| Wall Thickness (壁厚) | 0.5 mm – 2.0 mm |
| Coil Diameter (CD, 盘管外径) | 50 mm – 500 mm |
| Coil Length (盘管展开长度) | Up to 50 meters per coil (continuous) |
| Winding Pitch (螺距) | 3 mm – 25 mm (adjustable) |
| Tolerance on OD (外径公差) | ±0.05 mm (precision grade) |
| Tolerance on Wall Thickness (壁厚公差) | ±0.03 mm |
| Surface Roughness (Ra, 内壁) | ≤ 0.4 μm |
| End Preparation (端部处理) | Beveled (GB/T 12162), Plain, or Threaded |
| Welding Type (焊接方式) | Butt Weld (对焊) / Socket Weld (承插焊) |
| Packaging (包装) | Wooden crate / Export-standard packaging |
| Standard Reference (执行标准) | GB/T 14976, ASTM A213, EN 10216-5 |
4. Manufacturing Process
4.1 Raw Material Selection & Incoming Inspection
Raw stainless steel seamless tubes are sourced from certified mills and subjected to rigorous incoming quality control, including spectroscopic analysis (光谱分析) for chemical composition verification, ultrasonic testing (UT) for internal defect detection, and hydrostatic pressure testing (水压试验) to confirm wall integrity. Only materials meeting the specified chemical and mechanical requirements proceed to the coil forming stage.
4.2 Precision Coil Forming (精密盘管成型)
The straight tube stock is fed into a CNC-controlled coil winding machine (数控盘管绕制机), which forms the helical geometry with high dimensional accuracy. The winding process employs:
- Constant-bend-radius forming: Ensures uniform curvature throughout the coil, eliminating stress concentrations that could lead to premature fatigue failure or flow maldistribution.
- Spring-back compensation: Computer-aided compensation algorithms account for elastic recovery during forming, achieving final dimensions within ±0.05 mm tolerance.
- Inter-passage clearance control: The winding pitch is precisely maintained to ensure uniform flow distribution across all turns of the coil, a critical factor in calorimetric accuracy as identified in the referenced optimization study.
4.3 Stress Relief Annealing (去应力退火)
Following coil forming, the product undergoes a controlled stress relief annealing cycle at 870–900°C in a protective atmosphere (argon or vacuum) for 2–4 hours, followed by furnace cooling. This process:
- Eliminates residual stresses induced during cold forming
- Prevents distortion during subsequent welding or thermal cycling
- Restores the full austenitic microstructure and mechanical properties
4.4 Surface Treatment & Cleaning (表面处理与清洗)
The coil tube is acid-pickled (酸洗) and passivated (钝化) to remove any oxide scale or contamination introduced during manufacturing. The interior bore is cleaned using high-pressure deionized water flushing to achieve the required internal surface roughness of Ra ≤ 0.4 μm, essential for minimizing parasitic heat losses and ensuring laminar flow conditions in calorimetric applications.
4.5 Quality Inspection & Testing (质量检验与测试)
- Dimensional Inspection: Laser scanning and coordinate measurement machine (CMM) verification of coil diameter, pitch, OD, and wall thickness at multiple axial stations.
- Visual & Dye Penetrant Testing (PT): Surface defect detection per ASTM E165.
- Ultrasonic Testing (UT): Internal defect detection per ASTM E1270.
- Hydrostatic Pressure Testing: Each coil is pressure-tested at 1.5× the maximum operating pressure for a minimum dwell time of 60 seconds.
- Flow Characteristic Verification: For calorimeter-grade coils, a sample is tested for pressure drop vs. flow rate characteristics using R-134a refrigerant, confirming compliance with the optimized design parameters from the referenced study.
5. Applications
5.1 Calorimetric Measurement Systems (量热器系统)
The primary application domain for this product is in precision calorimetric systems used in refrigeration and HVAC research. The coil tube serves as the heat exchange element within a calorimeter, where the flow characteristics of refrigerants such as R-134a are measured to determine thermodynamic properties including enthalpy, entropy, and specific heat. The optimized coil geometry minimizes flow maldistribution, ensuring uniform heat transfer across the entire coil surface and thereby improving measurement accuracy to within ±0.5%.
5.2 Heat Exchangers (换热器)
- Air-cooled heat exchangers for industrial refrigeration systems
- Shell-and-coil heat exchangers for process heating and cooling
- Plate-and-coil heat exchangers for compact thermal management
5.3 Refrigeration & HVAC Systems (制冷与暖通空调系统)
The coil tube is widely used as evaporator or condenser coils in commercial and industrial refrigeration systems, where its corrosion resistance and thermal performance ensure long service life and energy efficiency.
5.4 Chemical & Pharmaceutical Processing (化工与制药加工)
In chemical processing and pharmaceutical manufacturing, the coil tube is employed in reactors, distillation columns, and heat recovery systems where resistance to aggressive chemicals and high-purity requirements are paramount.
5.5 Food & Beverage Industry (食品饮料工业)
Compliant with NSF/ANSI 61 and 3-A Sanitary Standards, the coil tube is suitable for pasteurization systems, CIP (Clean-in-Place) loops, and thermal processing equipment in the food and beverage industry.
5.6 Medical & Laboratory Equipment (医疗与实验室设备)
Used in laboratory-scale calorimeters, cryogenic systems, and medical device manufacturing where precise temperature control and biocompatibility are required.
6. Quality Certifications & Standards Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System (质量管理体系) |
| ISO 14001:2015 | Environmental Management System (环境管理体系) |
| GB/T 14976 | Seamless Stainless Steel Tubes for Fluid Transport (流体输送用无缝不锈钢管) |
| ASTM A213 / A213M | Seamless Austenitic Stainless Steel Tubing for High-Temperature Service |
| EN 10216-5 | Technical Delivery Conditions for Seamless Stainless Steel Tubes for General Purposes |
| NSF/ANSI 61 | Drinking Water System Components — Health Effects (饮用水系统组件) |
| PED 2014/68/EU | Pressure Equipment Directive — Conformity Assessment |
| CE Marking | European Conformity — Product Safety & Performance |
7. Unique Selling Points
- Calorimeter-Optimized Geometry: The coil tube design is based on validated research into R-134a flow characteristics, ensuring minimal flow maldistribution and superior heat transfer uniformity — a critical advantage for precision thermodynamic measurement applications.
- Ultra-Low Interior Surface Roughness: The Ra ≤ 0.4 μm interior finish significantly reduces frictional pressure drops and eliminates nucleation sites, enhancing both flow accuracy and heat transfer performance.
- Precision Dimensional Tolerance: ±0.05 mm OD tolerance and ±0.03 mm wall thickness tolerance ensure consistent hydraulic performance across all coils in a multi-coil system.
- Customizable Coil Parameters: Coil diameter, winding pitch, OD, and wall thickness can be tailored to specific application requirements, enabling optimization of the flow regime (laminar/turbulent) and heat transfer coefficient for the target refrigerant and operating conditions.
- Full Traceability: Each coil is accompanied by a Mill Test Certificate (MTC, 材质证明书) with full chemical composition, mechanical property data, and heat number traceability for quality assurance and regulatory compliance.
- Long Service Life: The austenitic stainless steel construction combined with stress relief annealing provides exceptional resistance to thermal fatigue, corrosion, and mechanical degradation, ensuring reliable operation over extended service periods.
8. Technical Notes & Recommendations
Note: For calorimetric applications involving R-134a refrigerant, the coil tube geometry (coil diameter, pitch, and tube OD) should be selected based on the desired Reynolds number (Re) range to achieve the target flow regime. The referenced optimization study demonstrates that a coil diameter of 100–200 mm with a pitch-to-OD ratio of 1.5–2.5 provides optimal flow uniformity and pressure drop characteristics for