Stainless Steel Evaporator Coil Tube (Coiltube) — Two-Circuit Configuration

Product Overview

The stainless steel evaporator coil tube is a precision-engineered heat exchange component designed for advanced refrigeration and air-conditioning systems. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this coil tube product is specifically engineered for two-circuit evaporator configurations, delivering superior thermal performance under variable operating conditions including fluctuating wind speeds and compressor frequencies.

Based on rigorous experimental research into the effects of Wind Speed (WS) and Compressor Frequency (CF) on heat exchange and dehumidification performance, this product line represents the culmination of academic-industrial collaboration. The two-circuit design enables optimized airflow distribution, enhanced latent heat transfer, and improved dehumidification efficiency compared to single-circuit alternatives.

Key performance characteristics have been validated through systematic experimental studies, demonstrating that the coil tube maintains consistent thermal efficiency across a wide range of operating parameters, making it an ideal solution for precision climate control applications.

Material & Properties

The coil tube is fabricated from high-grade stainless steel, selected for its exceptional corrosion resistance, mechanical durability, and thermal conductivity. The following materials and properties are characteristic of this product:

• Base Material: Austenitic stainless steel conforming to ASTM A213 / ASME SA-213 standards
• Alloy Grades: SUS304, SUS316L (Low Carbon), or SUS321 depending on application requirements
• Corrosion Resistance: Superior resistance to chlorides, moisture, and chemical attack; suitable for humid and corrosive environments
• Mechanical Strength: High tensile strength (≥ 520 MPa for SUS304) ensuring structural integrity under pressure cycling
• Thermal Conductivity: 14.9–16.3 W/(m·K), providing reliable heat transfer performance
• Temperature Range: Operational range from −196°C to +870°C
• Surface Finish: Polished or passivated inner and outer surfaces to minimize flow resistance and fouling
• Hygienic Properties: Non-reactive, non-toxic, and suitable for food-grade and pharmaceutical applications

Specifications

Parameter	Specification	Standard / Reference
Product Type	Two-Circuit Evaporator Coil Tube	—
Material Grade	SUS304 / SUS316L / SUS321	ASTM A213, JIS G3446
Outer Diameter (OD)	6.35 mm – 12.70 mm (1/4" – 1/2")	ASME B8.37.1
Wall Thickness	0.50 mm – 1.20 mm	—
Tube Length	Customizable; standard 1.0 m – 6.0 m	—
Coil Diameter	150 mm – 600 mm (configurable)	—
Circuit Configuration	Two-circuit parallel arrangement	—
Operating Pressure	Up to 2.5 MPa (375 psi)	ASME BPV Code
Refrigerant Compatibility	R134a, R410A, R407C, R32, R290	—
Wind Speed Range (Validated)	1.0 m/s – 5.0 m/s	Experimental Study Ref.
Compressor Frequency Range	20 Hz – 100 Hz (inverter-driven)	Experimental Study Ref.
Fin Configuration	Aluminum or stainless steel fins; fin density 10–16 FPI	—
Connection Type	Flared, brazed, or threaded	ASME B31.5
Surface Treatment	Passivation, electropolishing, or PVD coating	—
Weight (Typical)	0.8 kg – 3.5 kg per coil assembly	—

Manufacturing Process

The production of the two-circuit evaporator coil tube involves a multi-stage precision manufacturing sequence designed to ensure dimensional accuracy, structural integrity, and optimal thermal performance:

1. Raw Material Selection & Inspection: Stainless steel seamless tubes are sourced from certified mills and subjected to spectroscopic analysis (OES), hydrostatic testing, and ultrasonic examination to verify chemical composition and internal soundness.
2. Dimensional Preparation: Tubes are cut to specified lengths using precision laser or cold saw cutting methods, followed by deburring and end-preparation to ensure clean, burr-free entry and exit points.
3. Coil Forming: Tubes are cold-bent into the prescribed coil geometry using CNC-controlled bending machinery. The bending process is carefully controlled to avoid ovality exceeding 1.5% and to prevent work-hardening that could compromise fatigue life.
4. Circuit Configuration: For the two-circuit design, header pipes and U-bend connections are fabricated to create two parallel flow paths, ensuring balanced refrigerant distribution and optimized heat transfer surface utilization.
5. Fin Attachment (if applicable): External fins are mechanically or welded onto the coil tubes to increase heat transfer area by up to 400%. Fin-to-tube bonding integrity is verified through pull-off testing.
6. Welding & Brazing: All joints are fabricated using TIG (Tungsten Inert Gas) welding or vacuum brazing under inert atmosphere (argon) to prevent oxidation. Weld quality is verified through dye penetrant testing (DPT) or radiographic examination.
7. Surface Treatment: The finished coil tube undergoes passivation treatment (nitric acid or citric acid immersion) to restore and enhance the passive chromium oxide layer, ensuring maximum corrosion resistance.
8. Pressure Testing: Each unit is hydrostatically tested at 1.5× the maximum operating pressure for a minimum dwell time of 15 minutes to verify leak-tightness.
9. Final Inspection & Packaging: Products undergo dimensional verification, visual inspection, and material traceability documentation before protective packaging for shipment.

Applications

The two-circuit stainless steel evaporator coil tube is designed for demanding applications where reliability, corrosion resistance, and thermal efficiency are paramount:

• Commercial & Industrial Air Conditioning: Chiller systems, rooftop units (RTUs), and packaged air handlers requiring high dehumidification capacity
• Heat Pump Systems: Cold-climate heat pumps and dual-source heat pumps operating with variable-speed compressors
• Food Processing & Cold Chain: Refrigerated storage, blast freezers, and food-grade cooling systems where hygienic stainless steel construction is mandated
• Pharmaceutical & Laboratory Cooling: Precision temperature-controlled environments requiring non-reactive, cleanable heat exchange surfaces
• Marine & Offshore HVAC: Corrosion-resistant cooling systems for vessels and offshore platforms exposed to salt-laden atmospheres
• Data Center Cooling: High-density server room cooling systems requiring efficient latent heat removal
• Agricultural Refrigeration: Greenhouse climate control and cold storage facilities for perishable goods
• Variable Refrigerant Flow (VRF) Systems: Multi-split air conditioning systems with inverter-driven compressors operating across wide frequency ranges

Performance Characteristics

Experimental studies have demonstrated the following performance behavior for the two-circuit evaporator coil tube under variable operating conditions:

• Wind Speed Effect: Increasing air-side wind speed from 1.0 m/s to 5.0 m/s results in a proportional increase in convective heat transfer coefficient, improving overall coil efficiency. However, excessive wind speed may reduce dehumidification effectiveness due to shortened contact time.
• Compressor Frequency Effect: Higher compressor frequencies increase refrigerant mass flow rate and evaporating temperature, enhancing sensible cooling capacity. The two-circuit configuration maintains balanced flow distribution across both circuits even at low frequencies (≥ 20 Hz).
• Dehumidification Performance: The two-circuit design achieves superior latent heat transfer compared to single-circuit configurations, particularly at moderate wind speeds (2.0–3.5 m/s) and lower compressor frequencies (30–60 Hz).
• Operating Stability: The coil tube maintains stable performance across the validated parameter range without significant performance degradation or flow maldistribution.

Quality Certifications & Standards Compliance

Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring full compliance with international standards:

• ISO 9001:2015 — Quality Management System certification
• ISO 14001:2015 — Environmental Management System certification
• ASME BPV Code Section I — Power Boiler Code compliance for pressure-containing components
• EN 10204 3.1 — Material certificates conforming to European standard for product inspection
• ASTM A213 / ASME SA-213 — Seamless austenitic stainless steel tubing standards
• EN 10216-5 — European standard for seamless stainless steel tubes
• NSF/ANSI 61 — Drinking water system components (where applicable)
• CE Marking — European Conformity for pressure equipment (PED 2014/68/EU)
• RoHS 2011/65/EU — Restriction of Hazardous Substances compliance

Unique Selling Points

• Research-Validated Performance: Two-circuit design parameters are informed by systematic experimental research on wind speed and compressor frequency effects, ensuring optimized real-world performance
• Superior Dehumidification: Dual-circuit configuration provides enhanced latent heat transfer, critical for high-humidity environments
• Variable Speed Compatibility: Engineered for seamless integration with inverter-driven compressors operating across 20–100 Hz frequency range
• Exceptional Corrosion Resistance: Stainless steel construction ensures decades of service life in aggressive environments without degradation
• Hygienic & Food-Grade: Non-reactive surfaces suitable for food processing, pharmaceutical, and medical applications
• Customizable Geometry: Flexible manufacturing capability allows adaptation to specific system layouts and performance requirements
• Full Traceability: Complete material certification and lot traceability from raw material through final product delivery

Technical Notes

Note: This product is specifically engineered for two-circuit evaporator applications. Performance data is derived from controlled experimental conditions and may vary based on installation configuration, refrigerant charge, ambient conditions, and maintenance practices. Wenzhou Jixing Metal Materials Co., Ltd. recommends consulting technical documentation and performing site-specific thermal calculations for optimal system integration.